vmotion

DRS, Vmotion, and Snapshots

I think setting DRS(Distributed Resource Scheduling) to manual mode when removing snapshots, should be best practice, especially when you are only running two ESX servers and they are slightly taxed. Why? Mainly because when you remove a snapshot, especially a two tiered one, it can cause the hard disk to “thrash” and thus signaling DRS to Vmotion a Virtual Machine from one ESX Server to the other ESX Server automatically. This will of course cause more stress on the hardware and eventually the client may notice the decrease in performance. Hey I’m just speaking from personal experience. When the snapshot is removed, re-enable DRS. Comments?

-NS

VMFS and Block Sizes

Well i ran into this error today (4:30 am CST, don’t ask me why I am up right now!) “File too large” when trying to create a virtual machine with a 30GB drive and a 300GB drive. I tracked it down to the fact that the block size on my second LUN is 1MB which gives a max file size of 256GB. I will have to change the block size to 2MB which will let me create 512GB files, unfortunately I need to move a couple VMs off there to do so, I will just end up utilizing vmotion to move the VMs then reformat the LUN using a 2MB block size, then vmotion back. Sounds like fun! Well it isn’t, but its an interesting learning experience. Don’t make the same mistake, and you wont have to deal with this issue yourself.

The table below is the Block size in correspondence with the max file size

1MB Block Size: Maximum filesize = 256GB
2MB Block Size: Maximum filesize = 512GB
4MB Block Size: Maximum filesize = 1024GB
8MB Block Size: Maximum filesize = 2048GB

NS