How to plan the lun size for the ESX Server

[zhangfred_vm]

Dear friends,

Is there best practise to plan the lun size for the ESX Server?

What is the lun size for the virtual machine?

Thanks.

[Dave_Mishchenko]

There's some links to threads below that you might want to check out.

http://www.vmware-land.com/Vmware_Links.html#Storage

Basically, the size of your LUNs will depend. In general you'll see people using around 500 - 600 GB per LUN without about 10 to 15 VMs per LUN. If you put too many VMs onto a LUN you can end up with SCSI reservation issues. That occurs when a host has to lock the entire LUN to perform certain file operations (power on a VM, create a new, etc) which has the effect of pausing I/O for all other VMs. You will see people go with larger LUNs 1 TB plus, but often that will be to accommodate larger VMs like file servers.

You'll also want to give some attention to the disks that comprise the LUN to ensure that they are capabale of sufficient I/O to keep up with the needs of your VMs. If you're also splitting VMs across LUNs that are on seperate disks, then you'll want to spread the high I/O VMs over the LUNs to spread out your I/O load.

What sort of VMs do you have plans for?

[davewhitaker]

Just to add to what was already said, I'm pretty sure HBA load balancing in VMWare is accomplished on a per-LUN basis, so putting all of your VMFS storage on one LUN would remove the benefits of load balancing across HBA ports on the host.

[IOWDave]

It is a good idea to check with your SAN supplier as there are different recommendations from different companies. I believe that HP, for example, suggest no more than 8 to 12 VMs per LUN. If you go over that then you are in danger of the dreaded SCSI reservation problem as mentioned earlier in this thread.

[zhangfred_vm]

thanks.

I want to create the windows 2003, xp, 2000 virtual machine on the lan.

Each Virtual machine may use 100－500GB disk.

[Dave_Mishchenko]

Each Virtual machine may use 100－500GB disk.

When you create the VMFS data stores you'll want to select a block size of at least 2 MB, otherwise you won't be able to create a file larger than 256 GB. You can't change the block size of a data store later on without a reformat of the entire line.

Block Size Maximum Size of VMDK

1 MB 256 GB

2 512

4 1024

8 2048