esx reports more free space than SAN does

[blenderman]

I have a student that has a Dell Eqallogic PS400E ISCSI SAN and ESX 3.5i servers using the VMware software initiator. They have observed that LUNS formatted with VMFS show different amounts of free space depending on whether you view from ESX or from the SAN. The SAN reports most LUNs are low on space but ESX reports that there is a good bit of free space on the datastore. The variation in reports can be as much as 50 GB.

Anyone have any ideas on why this might occur and what they should look at to reconcile the differences?

[AndreTheGiant · Accepted solution]

You can find some old thread on this argument.

It's true: Equallogic report less space that ESX, but the reason is simple...

Equallogic doesn't know VMFS and how it works.

Know only block marked as used (that could be free or unused in VMFS).

Andre