ESX server's local hard disks; are they a performance consideration?

[doggy]

Hi,

Couple of hdd Q's:

When spec'ing up an ESX server to work with VMs on shared storage, does the ESX server's local hard disk setup have any bearing on the VMs performance?

Do the local hard disks need to be very big - are they used for anything other than holding the ESX system?

Many thanks

d

[VirtualKenneth]

No local disk don't have to be very big.

In fact you can even install it on boot-from-san systems but performance wise I would advise you to install ESX on the local disk (just use a simple RAID1 set)

VM's are stored on the SAN as well as their individual swap files (.vswp)

[esiebert7625]

Yes it will have a impact, not a huge one though, the disk subsystem is typically the slowest component and can be a bottleneck if you have disk I/O intensive VM's. You can offset this by using a RAID controller with a large cache (at least 512MB) using 15K rpm drives and by using more drives in your RAID group, having more spindles in the RAID group will give better performance. You can also create multiple RAID groups locally if you have a 2 channel SCSI controller. One group for the ESX host OS the other for the VM's.

[VirtualKenneth · Accepted solution]

Extra information, when using the best practices disk layout:

/ 5000 MB

/boot 200 MB

/home 2000 MB

/var 3000 - 5000 MB

/tmp 2000 MB

Swap 1600 MB

Vmkcore 100 MB

/opt 2000 MB

You get a total of 17900 MB.

So in fact you can just do with a 18,2 GB disk (or 2, in case of mirroring)

This is when not using local VMFS obviously

[doggy]

Perfect, thanks.

I plan to use shared storage (Equallogic P50e running iSCSI) for all VMs, so for the ESX server itself I guess I'll spend money on getting smaller quicker hdds.

I guess I may as well mirror them unless you think having one standalone will be quicker and affect the ESX server performance? Redundancy would be thru VMotion anyhow..

d

[VirtualKenneth]

I would advise you to use mirroring since you won't notice the speed between mirroring and stand alone.

VMotion isn't for redundancy!, when 1 ESX hosts fails VMotion will not work since the VM is down as well.

VMware HA could help you in that case but you will experience a unplanned downtime.

[doubleH]

if you're talking about redundancy then i would like to point out that the PS50 isn't fully redundant because it only has 1 controller. dual controllers start at PS100 and up. just wanted to point that out to you.