vSphere Storage Appliance

In the typical text about what causes SCSI reservations it is mentioned actions like adding new VMDKs or delete them or expanding snapshots, but not ongoing expanding/growing of Thin Disks. Is there any reasons why the expanding of thin disks does not cause this? If the VMFS block size is small as 1 MB the thin vmdk will likely expand quite often when the guest file system grows?

There are a lot of discussions on the various blogs about this topic. The most interesting answer iI saw, is the one at http://www.yellow-bricks.com/2009/05/14/block-sizes-and-growing-your-vmfs/ by Satyam Vaghani.

André

every single time it needs to expand a SCSI reservation will be required. Now with the advanced locking mechanism vsphere has the locking mechanism has been relaxed so it shouldn\t be too big of an issue. on top of that you could also, if your array is capable, leverage VAAI capabilities to offload the locking and do it on a block level vs datastore level.

Again, I spoke extensive with Satyam about it and you shouldn't be too worried. Especially if you are not overloading the array/datastore.

Duncan (VCDX)

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