jauner
Contributor
Contributor

Load balancing Virtual Machines

We have a san with 2 luns used by are vmware installation. Each lun is 600 GB. I am trying to figure out how to balance the VMs we now have. I was thinking something like the following: have active directory on one lun and backup active directory on another lun. Where it gets iffy is where i should put things like SQL Server, file server etc.

We currently run an ERP system which uses a terminal server, sql server and utility server. I am not sure if those should be on the same lun or if they should be separated or if it really matters.

Any input would be helpful.

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Craig_Baltzer
Expert
Expert

Prob. a few considerations

  1. Are the LUNs on different sets of disks on the SAN , or are they just carved out of the same set of disks? If they're the same set of disks you prob. aren't going to gain much in the way of performance by moving VMs from one LUN to the other.

  2. Are there any SAN snapshot type technologies in use, or will any of the VMs require RDM disk (clustering?) rather than using VMDK files? If you need to use RDM then that will use one LUN...

  3. What is the change rate for the VM configuration (including power on/off of the VM). These events cause SCSI reservations that temporarily hold up IO to the LUN. So you wouldn't want to put say a SQL Server VM that does a lot of IO and needs fast transactional response on the same LUN as a set of test/development VMs that were being frequently reconfigured/powered on/powered off...

  4. What VMs provide "redundancy" for each other. It would prob. make sense to split those VMs onto seperate LUNs (as you've suggested in putting one DC on each LUN) to provide some isolation from errors causing the loss of a LUN

  5. What is the disk growth expectation for the VMs? You'd want to try and balance things out so that you didn't have all of the VMs that were expecting to grow on a single LUN where you'd run out of space while your other LUN had lots free

jauner
Contributor
Contributor

Each lun is a set of 6 separate discs and the only redundancy we have as far as vms at this point is the backup active directory server. We are using VCB to do backups via Backup Exec so I think that would qualify as snapshot technology and we are not using RDM.

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