fd1smith
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Contributor

Buying New Hosts

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We are looking for some information regarding host performance using different types of RAID.

Does RAID 1 versus RAID 5 noticeably affect host performance under the following conditions?

  • Host disks are used for the ESX operating system and storage of ISO files for quick access from the vSphere client to install software on virtual machines.
  • All virtual machines are stored on SAN storage and not locally on the hosts.
  • All data is stored in raw mapped LUNs and not locally on the hosts.
  • Virtualcenter is being utilized.

The entire reason for this question revolves around having more host disk space accessible for the use of ISO storage without impacting performance.

Yes we know mirroring is “faster” than striping.  We just want to know if anyone has experience with how much it affects host performance.

Thank you for your comments and suggestions.

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kjb007
Immortal
Immortal

This is difficult to generalize.  It will depend on your application IO profile, as well as your underlying disk array.  Storage providers have several ways to work around any IO penalties incurred through the use of various RAID flavors.  Your application will determine how much and which type of IO you are doing, which will require a certain baseline performance from the disk to perform satisfactorily to you.  The big question is how much IO are you looking to do?  You can take the underlying disk array, and figure out how much IO you can get out of your disk subsystem, and that may or may not be enough for what you want it to do.

Using vcenter will not make any difference or bearing on the RAID type you use.

The question you need to ask, is how muc I/O do you expect, and then you can figure out if your underlying system can handle it or not.

-KjB

vExpert/VCP/VCAP vmwise.com / @vmwise -KjB

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eeg3
Commander
Commander

I'd go with RAID-5. It will be plenty fast for storage of ISOs and the ESX{i} OS.

I wouldn't be too concerned with it unless you start putting VMs on there.

Blog: http://blog.eeg3.net
kjb007
Immortal
Immortal

This is difficult to generalize.  It will depend on your application IO profile, as well as your underlying disk array.  Storage providers have several ways to work around any IO penalties incurred through the use of various RAID flavors.  Your application will determine how much and which type of IO you are doing, which will require a certain baseline performance from the disk to perform satisfactorily to you.  The big question is how much IO are you looking to do?  You can take the underlying disk array, and figure out how much IO you can get out of your disk subsystem, and that may or may not be enough for what you want it to do.

Using vcenter will not make any difference or bearing on the RAID type you use.

The question you need to ask, is how muc I/O do you expect, and then you can figure out if your underlying system can handle it or not.

-KjB

vExpert/VCP/VCAP vmwise.com / @vmwise -KjB

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fd1smith
Contributor
Contributor

That's the problem.  I don't know how much I/O to expect from the ESX operating system.  ESX is the only thing that will be accessing the drives on a regular basis.

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eeg3
Commander
Commander

The ESX[i] operating system puts negligible IO load on the disks.

Blog: http://blog.eeg3.net
kjb007
Immortal
Immortal

ESX itself does not do much IO to the disk.  It is logging, but other than that, the I/O profile of ESX itself would not require high IO capable disk.  What makes a difference is how much IO your virtual machines will be doing.  For that, ESX is very close if not exactly at the requirement your server would have for a physical environment.  So, the idea is to build your disk to support your server, not ESX specifically.  Treat the workload as if it were physical, determine how much IO you need, and then build from that.  I have not personally had the need for high IO in my general environment, and would therefor opt for more disk than more speed. In that case, I would go with RAID5.

-KjB

vExpert/VCP/VCAP vmwise.com / @vmwise -KjB
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fd1smith
Contributor
Contributor

Thanks, I appreciate the help.  I am going to leave the post open for a while to see if anyone else has an opinion.

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msemon1
Expert
Expert

RAID 1 or RAID 5 will work just fine. I always use RAID 1 for servers and RAID 5 for Storage. You can use RAID 5 on 1 or 2 of your ESX(I) servers if you want extra space for your ISO's and get the rest as RAID 1. I don't think you will see a big performance difference unless you are doing something I/O intensive. This would be cheaper than storing your ISO's on some other type storage.

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samansalehi
Enthusiast
Enthusiast

I use RAID one for my hosts and raid 5 for my SAN and run my VMs on this SAN.

I know I can manage the Network with Team NICing up to 4 Gbps or more(depend on NIC of server) but even using a Host with 2Gbps Fiber Channel did not make any difference in IO performance of my VMs and MY ESX Host.

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