Offline VM Migration auto convert RDM to VMDK format

Due to some reconfiguration work we performed on our Virtual Infrastructure, we had required to relocate some of the VM to a different datastore. These VMs which required to be moved had been attached with Raw Device Mapping (RDM). Previously I thought the offline storage migration will not move the RDM over to the datastore as RDM is referring to the raw device from the SAN storage.Actually I was planned to convert the RDM to VMDK which I planned to manual transfer the files I need from RDM to the new virtual disk I created.

In a test yesterday, we found that a offline VM migration will auto convert the RDM which attach to the virtual machine to the VMDK format when I selected the data store to be moved in offline mode. This was really surprise myself and simplify my work actually, as I do not require some manual file transfer from the RDM to the new virtual disk.

Oracle to buy Sun Microsystem

Break news today which shocked most of the IT folks as Oracle had announced to buy over Sun Microsystems for 9.50 a share. I am really shocked to see this as last week, we were still talked about the deal called off with the possible merging from Sun Microsystems with IBM, which may end up IBM monopolize some high end computing market. Oracle could make a good move by taking over Sun. This may direct or indirect many environment which related to Virtualization, Java and MYSQL which is the strength of Sun Microsystems. There are chances to reduce the dependency of Oracle to Redhat and Enterprise Linux and move over to Sun Solaris or open solaris. This is more positive VS the buy over that suggested by IBM previously.

Oracle is no longer a software company today. With buy over for Sun Microsystems, they will able to deliver the hardware, platform, software, database, virtualization and etc. I think they will be more aggressive strategy to move themselves into the virtualization and integration market which may end up competing themselves with their partner such as VMware. This will definitely heat up the market or virtualization and hypervisor competition.

6 cores limitation per socket for vSphere enterprise

As the new licensing model from VMware vsphere 4, it clearly show that you may require additional 620USD per sockets to entitle yourself for the enterprise plus if which come with 12 cores per sockets, host profiles, distribution switch and etc.

For existing enterprise users, they will no longer entitle everything as they did in the past due to the new scheme that will apply by vmware. There is a clause which stated by the official documentation released from vmware.

" vSphere Enterprise is available for USD$2,875 per one processor with up to six cores for use on a server with up to 256GB of memory. "

This clearly stated as six cores per sockets is the max you can go if you are previous or new enterprise customer. Here is the concern now, as six cores is in the market now, and soon we will see 8 cores and 12 cores in the market too. When the hardware technology improve and provide more cores per CPU, we will end up require to pay for additional charges to entitle the features due to this licensing model.

Personal point of view, to provide alternative licensing model with new features should be acceptable, but it shouldn't fix the limit for number of cores to be allowed in each CPU sockets licenses. A customer may end to pay more not because the new features they really need, it may just purely due to the maximum number of cores per socket is allowed. I hope VMware should reconsider the clause they had included in the release.

Calculation of Max LUN Supported in ESX Server

I found my ESX servers could not recover the 65th LUNs that I tried to present to it and myself did log a support call and still pending the reply from VMWare. Beside that, I found another interesting article with the details below.

Article Copy from VMWare

In Multipathing Configurations the Number of Paths Per LUNIs Inconsistent
The hpsa driver in ESX Server might reduce the number of supportable LUNs below the expected maximum limit of 256 when the controller is used in multipath configurations. In multiplath configurations, if all four paths are configured, the total supportable LUNs is reduced to 64. In certain multipath configurations, because each target path consumes an available LUN slot, the total number of supportable LUNs might be reduced to 60.

Workaround
Reduce the number of LUNs on a server until the product of LUNs and paths is less than 256 (LUNs * Number of paths < 256), and if necessary, reduce the LUN count depending on use of multipath until each LUN has the expected number of paths.
The following example shows a configuration with the maximum supportable LUNs presented to an ESX Server installation on four paths, providing all LUNs with the expected number of usable paths:
Path 1: 63 LUNs seen through this path; Total LUN count (63 + 1 path) is less than 256
Path 2: 63 LUNs seen through this path; Total LUN count (63 + 63 + 2 paths) is less than 256
Path 3: 63 LUNs seen through this path; Total LUN count (63 + 63 + 63 + 3 paths) is less than 256
Path 4: 63 LUNs seen through this path; Total LUN count (63 + 63 + 63 + 63 + 4 paths) = 256

If I do use the formula above to calculate my environment, yes, I am at the full limit of 256 LUNs. I have 2 ESX servers which only have 2 HBA connection, and had no problem to present more than 67 physical LUNs to it until now. What I had done now is, I removed 2 HBA connection from each of my ESX servers, and run the rescan, and I found that the LUN is presented as I expected. Again, I am not confirmed with the solution yet and will do another round confirmation with the VMware engineer on this.

Manual commit snapshots delta file to vmdk flat file

I had a tough time this week to deal with the snapshot issue with one of the VM. The VM is containing an important snapshot that previously taken for system restoration. When I browsed through the snapshot manager from vCenter, the system show my VM was running without any snapshots. Here was the kicked start of my problem and excited journey until I managed to recover it this morning.

I tried to SSH to the ESX host and browse to the specified datastore, and I found the snapshot file which end with file extension .vmsn were available in the correct location. No matter how many times I tried and rebooted my Virtual center, the snapshot were not visible to the snapshot manager still.

I read through some articles and forums which suggested to clone the snapshot by using vmkfstools -i option, but it didn't success in my case here, and I continue my research and here I found a useful blog post from 1 of the blogger Oliver O'Boyle who experienced similar issue previously.

After I read through his article, which explained the chain within the CID and parent CID, it does help me to resolve my issues. I found that the root cause of my VM was due to the snapshot problem & vmdk config file corruption. For snapshot issues, we can recreate a new snapshots and we select to delete all snapshot afterward, it should force the vmdk flat files and delta files to be committed. In 1 of the virtual hard disk, we experience difficulty as the ESX servers will force the virtual HDD to be detached from the VM. The root cause of that was caused by the file missing on the parent file which should be VMxxxx.vmdk.

During this troubleshooting, you should ensure that the delta files and flat files are always retained and not overwritten. There are 2 delta files which end with VMxxxxx-000001.vmdk and VMxxxxx-000001-delta.vmdk. Your flat file should end with VMxxxxx-flat.vmdk. The 1st thing I did, was to ensure the virtual disk was able to re-attached the vm. I had manually created a new vmdk config file follow the guide from the Oliver O'Boyle, and I copy the parent CID and virtual disk value number require. I had manually configured the link within .vmdk and the flat file. After that, I was able to attach the virtual disk back to the VM from virtual center. Please take note that the virtual center will not see the flat files as the attachable virtual disk, as vCenter recognize the virtual disk base on the location of .vmdk. Recommended to keep the .vmdk and flat file within same datastore. You can also relocate the vmdk files to different datastore if you wish to do so.

Once the virtual disk had been attached to the VM, boot up the VM immediately. Please log in to the system and ensure everything is in normal and functioning correctly. The data I contained now, wasn't the latest data I needed as the result of the missing snapshot which was not committed by the system. Now, I take a new snapshot for my entire VM. Once I had done that, datastore in SSH showed up with plenty of delta files and newly created VMDK files which end with VMxxxxxxx-000003.vmdk and so on.

Here are the steps been taken to commit the snapshots manually

1. Power off the VM
   
2. Right click the VM and select edit settings from vCenter and select the virtual disk that you are trying to recover. The system will show which vmdk files this virtual disk is pointing to
3. Copy down the file names and go back to your SSH screen
4. Replace the VMDK and delta files that you previous retain from your original snapshots which you are recovering with the FILE NAMES that you copy on step 2
5. Open up the snapshot manager for the VM, and select delete all snapshots option. This process will take time as it depend the size of your delta files require to be committed.
6. It should stuck at 95 % or time out, but the system will still continue to commit the delta files back to the flat files. In my case, it took more than 2 hours to delete the snapshot
7. I noticed the ESX server load and disks activity increased from the performance chart
8. Once it completed, all the delta files will be deleted and everything should be back to normal
9. Power on the VM and double check all the data and mount point and I found the system was back to normal

VMware ESX 4 New features

According to VMware, the future of the VMware Enterprise Edition Virtualization which name as ESX 4 will be launched earlier next year, will contain some of the features which been show case during the seminar to the public. Below is some of the information which had been shared by VMware for reference

1. 64 bits kernel VS the current 32 bits kernel on ESX server
2. Thin Provisioning
3. Fault Tolerance
4. 8 way virtual SMP
5. 256 GB memory per single VM

There are also more to come in the roadmap of year 2009 which will specify on the vcloud, virtual data center and etc. At lease for today, this had been public demostrate to the end user about some of the technology roadmap and features in the next version. ESX 4 is still under private beta test at this moment, which aim to be launched at 1st quater next year.

VMware Workstation 6.5.1 Release

VMware had just official released the Workstation 6.5.1. There are some new features will be impress with the latest build number of 126130

For more information, please view it over at the link below

VMware Workstation 6.5.1

VMware Server 2.0

VMware Server 2.0 is free and open source version, which is different with enterprise ESX 3i which also a free version from VMware. In term to utilize VMware server 2.0, you will require to have a Windows or Linux install on your machine or server, and install VMware Server 2.0 on top of the operating system to enable the hypervisor to be executed. This is different with ESX 3i which is not require any Operating System to be installed.

We may see this is comparison which compete with VMware workstation 6.5 which recently launched. If you ask my opinion, I will say that both are on different product range. VMware Server 2 can be consider as alternative to the business users, who may not need the advance technology & features to simplify their IT environment with minimal administration require. This product is more suitable for the Small Medium Enterprise users which may not have a Data Center for their working location. I will say that a Junior IT professional will easily able to manage the VMware Server and take the opportunity as a entry level for Enterprise Virtualization with VMware Server 2. Besides that, it does provide opportunity for every users to have virtualization in place for their business to provide better ROI in term of hardware investment and utilization.

If we look VMware workstation, it provide more features and ability to the IT pro users to perform their test and development environment on their laptop, workstation or desktop which reduce the amount of servers require for a corporate to perform their application development. Somehow, ESX is targeting Enterprise level, 3i is provide for free which some cases we may not require VMotion and HA capability.Management wise, Workstation is simple and easy. You may not require to browse through the web console and easily can be launched as a program from your machine, but you will lost the administration features on the network. VMware Workstation has ACE integrated, drag and drop features and etc, which may not require for most of the VMware Server users for hosting purpose. VMware Server 2 will require a web browser for your management, and you able to manage it through LAN network. There is a tomcat installed while you configure you VMware server at the 1st time.

As well, you may compare the VMware Server 2 with XEN hypervisor free version. I believe in term of features, VMware always have better comparison. User freindly & Reliability are always important for a consumer when they consider the investment to a certain software.

Equallogic VS FC SAN

Economy Crisis this year has encouraged users to consider the ISCSI SAN Vs FC SAN today. Data Storage growth will never stop unless the business is stop. In order to keep the environment growth, the IT architect will have to provide a cost effective solution in the finance critical timing like now.

Performance wise, we may know that the Equallogic ISCSI might not beat the huge SAN box which easily cost you double as your TCO on ISCSI. I would like to share my finding relevant on the features it bundle with equallogic. In FC SAN, we are able to achive performance and functionality, which require always additional license cost and expensive infrastrucutre to support it. Today, ISCSI provide more flexibility in term of FC due to the common understanding we all have on the IP technology which we deal with it everyday.

In Equallogic ISCSI, you will entitle every features which bundle together with the storages you purchase.

• Snapshot Volume Manager
• Thin Provisioning
• Raid 5, Raid 50, Raid 10
  
• Auto Load Balancing
• Web Base Console
• DR Replication
• Storage Replication
• Volume Clone

The details of the available features is more than what I am stated here of course. Imagine if you own a FC SAN today, you may end up paying additional charges for every piece of licenses you require of the functionality. Beside this, Virtualization and VMware is become a main player for every Data Center today. Same with Equallogic, it had also become a powerful competitor to compete with the major vendor like Netapps, EMC, HP, HDS, IBM and etc.

Whithout comparing the cost and performance, I am really impress with the simplify management provided by Equallogic. You will not require to be long waiting of the web console, and it is user friendly and easy to be managed. Compare to FC SAN, you will require certain level of skillsets and patient for administration which you may suffer from the slow loading from the console always. Additional to that, FC SAN will become slower when the number of spindle and workload is increase, but equallogic has it advantage with every array will increase the processing power and throughput. Personal experience, I am only require less than 10 minutes to setup and configure my Equallogic Storage array, and able to start provisioning right after the configuration done. Is Really Fast!!

I run the performance test on my ESX server to compare the I/O performance Vs FC SAN, I realize that the performance is acceptable with the amount of money we pay for it. Simply becoz you may not virtualize the servers which require the real I/O intensive performance. I am able to achieve approximately 140MB/s with FC SAN for read/write, with Equallogic, I manage to achieve 115MB/s as maximum throughput in my VM. Again, this may be impacted due to the software ISCSI initiator. ISCSI HBA will able to improve the performance with minimize the overhead on ESX host. For my test, I only manage to run with single array. If we have more array in the future, it will able to increase the disk performance and storage throughput. 10Gb Ethernet are also on the way to the market next year. Equallogic are also design for SRM solution which provide by VMware to simplify the DR solution. With this storage solution, we will no longer require a big pipe for SAN storage replication as we did for the FC SAN previously.

Latest array PS 5500E are providing 48TB in RAW with SATA, which will be a good option for DR solution to provide cheaper hardware cost & better functionality. If I has been asked to reduce my CAPEX for SAN purchase, the only option I can think now is ISCSI as my option. Cisco 3750 is the recommended switches for DELL Equallogic, it is much more cheaper if we compare to the brocade FC SAN swithces.

Never the less, FC SAN are still the best option in term of reliable and performance, but as it is a tough time now for budget spending, I believe Equallogic has provide us an additional option with limited budget.

Netware 6.5 on VMware

Netware 6.5 on VMware is not new thing. But you will find that is not allowed to have more than 1 Vcpu per VM by default. Actually there is ways to overcome this as you normally can't fo it through virtual center. VMware workstation allow you to change the number of Vcpu as usual. But, on ESX server is different. You may need to log in to the web access to specify host or virtual center, and power off the virtual machine. On the web console, you can edit the number or Virtual CPU from 1 to 2 or 4. Then you power up the VM again, and now you will able to see the extra Vcpu you added just now. Go back to the virtual center, you should able to see the extra cpu too. VMware not recommend to have more than 1 Vcpu per VM for netware as it has some performance impact on host level and is proven during my personal test on it. The CPU utilization on host will be very high consistantly but it only consume 5% from the VM level.

DELL Equallogic PS5500E provide Auto Snapshot Manager for VMware

The latest version of ISCSI SAN Equallogic PS 5500E which launched recently had provide better capacity, performance, extra functionality and more spindles in arrays. It could be support both 500GB and 1TB SATA II spindles up to 48 drives in a single array of 4U. A very impress usable storage space in single array which up to 48TB in Raw. If we compare to the capacity, it is hardly found that a single array would provide a huge capacity at 48TB in Raw today. In additional to that, DELL had provide all the necessary features as for storage management as free which integrated as part of the storage purchase for equallogic ISCSI SAN. The latest features is regarding the Snapshot Manager for VMware. Previous version is only supported on Microsoft environment, but now, it had also supported on VMWare environment.

This features provide more option which will allow the users to snapshot, backup, and restore the files, volume, VM or even a single file that you need. Many of us may think about using the VCB for our VM backup today, the equallogic had provide some interesting package which allow us to avoid of VCB in our environment, and provide better backup and restoration process.

If we talk about disk base backup, which is VTL, it always cost involve in term of disk space and software licenses. With the latest features from Equallogic, we will able to avoid the extra investment require on VTL, but provide the similar functionality on disk base backup, and from disk to tape backup. If I bought the equallogic previously and sign up with the maintenance, I entitle the upgrade of the new features today. It will be a excellent surprise for my investment. As economy crisis, IT budget is been tight and require to work smarter, this should be a great news for the consumers. Personally, I will still say that the 10Gbe will be my option as to get rid of the fiber channel storage that we current use for VMware. As 48 spindles in a single array, we may need the bigger through put from the array to reach the client always.

According to DELL, we should able to see the official launch on 10Gbe but 1st quater of 2009.

Intel Moving to Infiniband

Intel had recently acquired the company call Neteffect which is focusing on 10Gbps adapter’s technology. As 10Ge is no longer a new thing in the market, but we still do not see it become the popular solution in the industry due to the expensive switches, NIC and solution that been widely control by the technology leader in networking solution. As we may also see some technology related to Ethernet infiniband which provide 20Gbps by using HCA (host channel adapter), that will be another major competitor to be compared with the 10Ge.

Personally I had been urging the storage and network vendor over and over again regarding the 10Ge products. The reason of it is pretty simple that the Fiber Channel is just too expensive to be deployed and managed VS Ethernet 10Ge. But the concern is the vendors are very slow responding to the 10Ge release roadmap although customers are demanding on that.

With Intel moving to the market now, I will see that is a big opportunity to make this 10Ge become inexpensive in the future with the high volume production provide by Intel in the servers’ market NIC. As virtualization becomes an important piece in the data center, the bandwidth will require being growing as much as possible at the same time VS CPU Cores and Memory. Intel had proven their right track on the servers NIC as many of us can easily found that the servers NICs are produced by Intel. Even in VMware ESX servers, your VM will be provided either AMD or Intel virtual NIC drivers on top of the hypervisor Virtualization.

As a IT Consumers, I am more than happy to see the technology become cheaper and cheaper and of course personally I do believe Intel will able to make the popularization for 10Ge moving forward.

Efficient Data Center - Virtualize & Consolidation

As many of us may know that there are some article talk about the High Efficiency Data Center. I would like to talk about 1 of the major point here which is Virtualize & Consolidation, since our site is more focus on Virtualization.

High Gas/Petrol price become an global issues, no matter which region or which country are you from, this had become and issue which drive the Operational Cost for a Data Center to keep alive from daily basis. In Malaysia, the government had recently increase the commercial electricity for 26 %. Imagine that if you DC consume RM 30000.00 a mount from power perspective, you had to pay RM 37800.00 a month. that had been significant impact the entire IT budgets plus the operational cost. As IT always be the main driver for most business today, we may need to provide a highly efficient Data center solution which able to recover the ROI within the shortest period as possible. Virtualization & Consolidation had come to the point for this.

As if we compare the power consumption from major chip maker like AMD and Intel, the watts per processor had stack and remain the same for the last 3 generations at least. The only improvement they made was really the performance per watt. 6 cores and 8 cores had been down the road, I will be strongly encourage who had not adapt to virtualization need to start virtualize or prepare to virtualize 80% of thier production environment.

My environment currently had running the entire DR solution with VMware technology. In production, I do have more than 50 production VM which provide web hosting, middleware, file & print servers and etc. Imagine you had a tight budget with only 50k USD, how many of physical servers will you able to buy from there? and wat about the amount of power you need to absorb on monthly basis? That is the real cost as many of you may had not see the electric bill. For my case, my cost center had to paid for the power bill ourselves.

To achieve 15:1 in VMware is no longer a big thing with the high capacity server from DELL, HP and IBM. By doing this, you can avoid the multi million renovation to expand your DC which may had nearly full. Technology is cool, but again as human being, we had to work smart. High efficient Data Center sometimes do equivalent to High Productivity of the support team too.

How Hyper-V quick migration fails

This article show how the Hyper-V migration failed. Another failure from Microsoft to deliver for their Hyper-V.

http://malaysiavm.com/blog/how-hyper-v-quick-migration-fails/

Please click on this to have a look

SSH on ESXi

This had been disable by default. Alternatively you can enable following the instruction below:

1. Go to the ESXi console and press alt+F1
2. Type: unsupported
3. Enter the root password
4. At the prompt type vi /etc/inetd.conf
5. Look for the line that starts with #ssh
6. Remove the #
7. Save /etc/inetd.conf by typing :wq!
8. Restart the management service /sbin/services.sh restart

Try it!

ESX and VM Guest - Round Robin Storage Setting

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 To improve the I/O performance for ESX Virtual Infrastructure, VMware had come out with the round robin option for both ESX and VM guests. Although is an experimental option in the ESX setting today, but I will encourage you all to try this option which provide fail over and load balancing on the storage path to connect to you SAN storage. For VM guests, you will allow to use this when you have RDM - Raw Device Mapping option to direct read write to the physical LUN from your SAN storage without using VMFS.
ESX Hosts

To enable this on ESX host, you need to browse to the configuration tab of the ESX host, and right click the data store and select properties, and click on manage paths option in the GUI wizard. Click on Change button after that, and choose the Round Robin (Experimental) option and click OK. You will need to go through this process 1 by 1 to ensure you had round robin from each ESX host to each of the VMFS Data store.

VM Guests

Just right click the VM

and choose edit setting, and select to the hard disk which has shown as Mapped Raw LUN on the summary tab. Click on the Manage Paths and follow by the change button, and same you can easily

configure to have the Round Robin enable.

Update Manager - VMware Virtual Center for Patching Activities

After couple of months we had performed the patch activities for our ESX hosts and VM guests by using the Update Manager, here is my review of the Update Manager from VMware.

Update Manager had simplified the life of the system engineers who manage the VM farm with the huge number of VM guests and ESX hosts which may require a frequent patch update. Before the Update Manager released, most of the time we had patched the server by using satellite servers, Altiris, SMS and others patching tools. That will require additional cost required to be implemented on the VM guests or esx host due to the licensing agreement from the vendor.

Update Manager is fully compatible with VMware ESX patches update for ESX 3.0, 3.5 and ESX 3i. From the Host level, you will able to get all the patches downloaded by the update manager schedule task once the VMware had officially release their patch on their official system. Update Manager had also integrated well with Microsoft patches as well as others famous software patches like Red Hat, Adobe and etc. It even allow us to patch the template image which we store for deployment purpose, without manual interaction to convert the template back to virtual machine. If you try to patch a windows 2003 template image, the entire process is fully automated. This is really impressive. I had also patch my DR servers which is 30 miles away from my major Data Center, and we had 30 Mb MPLS across the WAN, it worked perfectly without any issue at all, and of course, the patching timing will be slightly longer due to the location of the DR servers.

To get the update manager deployed in your environment, here is couple of step you may need to configure or enable.

A dedicated DB for update manager in the SQL or Oracle - Depend on the choice of database servers you are using. This Database will store all the information and patches to be used for patching purpose. If you have proxy server in your environment, you need to configure the proxy address and port number in the virtual center configuration for Update Manager. Schedule task to refresh and check the latest patches release from the official site, recommend to run the schedule task at least once in a week. I do schedule it to be run on weekly basis, to ensure you getting the latest patches when you try to patch you VM guest or ESX host.

Baseline - baseline is been use to define the patches required for specify product or platform by the update manager. ESX host baseline is been built in by default and categorize under Critical and Non Critical. You are also require to create you own baseline for specify OS and software you are using.

Please make sure you had update manager plug-in install on your virtual infrastructure client. To attach the baseline to the ESX or VMs you would like to deploy, you need to switch the view mode to Virtual machines and template mode, then select the system you would like to patch, and click on the update manager tab on it, and start attach the suitable baseline on it.

After you attach the baseline, right click the virtual machine or ESX host and select Scan. Scan will not actually apply the patches, this is allow the update manager to compare the current patch level for the ESX hosts and Virtual Machines and preview of the number of patches needed to be applied to be compliance. After the scan result display, right click the machine and select remmediate. This will start to apply the patches automatically.

For ESX hosts, you need to Vmotion all the VM guests to another ESX host. This will provide 0 down time during the maintenance, thanks to the cool technology by vmware on Vmotion. This had worked for me all the time. Once the ESX hosts is ready, is recommend to send the ESX host to maintenance mode, then start the remediation after that. Once the patch is completed, it will show the ESX host at a different patch level or update code by vmware release. You can verify this with the VMware website information easily.

For VM guests patching, down time will be required as usual, due to the reboot require from the operating system perspective. Again, this tools is bundle together with the Virtual Infrastructure by VMware, is really useful for the VMware engineers to patch thier VM guests.

The only disadvantage at this moment, SUSE linux is not supported by update manager. According to the VMware, they will soon release the next version of update manager to support patch activities on SUSE Linux VMs.

Resolution - ESX hosts unexpected disconnect from Virtual Center ( ESX 3.5 update 2 )

When I try to log in to my virtual center to verify my VM farm today, the virtual center show my ESX host had been disconnected from the virtual center by itself. The ESX host itself should be running in critical mode as production and had HA and DRS enable on the cluster. The 1st thing I try to verify is to ensure all my VM and the ESX host is still in production mode, and yes, all the VM is not been down and it still run as normal while it disconnected.

Here is what I did to reconfigure my ESX host and re-join it back to the HA and DRS cluster in my production farm.

Disable the HA and DRS features from the cluster, and totally remove the ESX host from the inventory on Virtual Center server. Follow by that, I SSH in to the ESX host with su -, then I path to the /etc/init.d and look for the services mgmt-vmware status command

It show the services is running. Then I issue the command services mgmt-vmware restart. This will take couple of minutes to get the service fully restarted. At the same time I had actually Remote log on to 1 of the VM to ensure no impact on the VM guest which sit on the ESX host. The result is perfectly work without any downtime on the VM guests, and should credit to the ability from VMware technology.

Once the services restarted, you can easily add host to the virtual center and reconfigure the HA and DRS cluster mode again. The ESX host is back to normal now and work perfectly as usual.

High Availability (HA) and DRS in ESX

The HA and DRS features become an important and a must for enterprise usage in production. For the latest updated patch release from VMware, you will realize some changes had been made in the way the HA communicated.

there is an incident for myself that the HA keep disconnect and reconnect automatically for every couple of minutes. The work around is you need to make sure the hostname that you configure for your esx server is still with lower case or upper cases. If you do have mix environment with upper case and lower case in the physical cluster for ESX, you will experience this technical issue due to the way of the HA communication had been tie to the DNS name. In linux, case sensitive is always apply

For DRS, is not recommend to configure to aggressive level as during the vmotion, it do generate the overhead and network traffic for vmkernel port for both original host and destination host. 1 of the test I had done previously, I Vmotion 20 VM to another host in 1 time, and I do face the CPU bottleneck which stop the vmotion activity. Advice here is to Vmotion 1 by 1 if you are not in rush as it will generate less overhead for the vmotion activity and of course higher success rate.