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Disclaimer: I know nothing about SAN configurations.

If you have large windows-install SAN backed VM, what is the common practice for the SAN configuration? Do the files exist purely on an NTFS LVM partition on the SAN? Or, does the SAN expose a block device to the VM? Can a quota be placed on file/io operations (as compared to throughput) on the SAN itself (I imagine this would preclude the block-device implementation).

Any guidance on SANs/VMs will be appreciated.

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I asked a pretty similar question not too long ago, as well: serverfault.com/questions/103638/… –  Matt Simmons Feb 9 '10 at 16:44
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up vote 3 down vote accepted

The SAN present a LUN to the VMWare server. This LUN has a specific fixed size. It is a block device.

What goes on from there goes on in the VMWare server. The VMWare Server puts the VMFS filesystem inside the LUN. It then puts VM images in that filesystem. It can then put restrictions on the size of the VM within the limits of the LUN.

A quota for the entire LUN is configured at SAN level. Quotas for specific VMs is configured at VMWare level.

As far as I know, IO quotas are configured at SAN level in high end SAN installations only. Entry level SAN definently don't have this feature. I believe most configurations allow you to configure it on a per-LUN basis but more on a per-host status.

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