Hello Everyone,

We have virtualized an FS5200 behind an IBM SVC. The FlashSystem has FlashCore Modules which are capable of doing inline compression, hence to make efficient use of the compression feature, we created a Standard Pool on the FlashSystem --> exposed the volumes to SVC --> and created a Standard Pool on the SVC. Created Thin Volumes on the SVC under the Flash Pool, and everything seems to be working as expected, but there is a small confusion.

As it can be seen in the screenshot above, there is "Usable Capacity" and "Capacity Details". Usable capacity reflects the compressed size of the provisioned volume which is inline with what we see on the FlashSystem. Capacity Details is the Provisioned space used by the thin-provision volume residing in the pool.

I wanted to understand, which of the two should we refer to, when it comes to usage of the pool. Over a period of time, "Capacity Details" will reach 103TiB before "Usable Capacity"... the confusion is, will that state prevent us from provisioning anything more in the pool, although we still would have usable capacity available ?

Any advice would be helpful.

Dear Imran

Compression of volumes workes like Thinprovisioning. You present a Volume of lets say 10TiB to a Host, but only 6 TiB are written to "Disk". So there is physical Capacity available, where you can create a new Volume.

A second thing, why these numbers differs : A provisioned Volume uses a number of Extents from the Pool. The Extentsize was fixed when creating the pool. By default the extentsize is 1 GiB on FS5200 on the FS7300 it will be 2 GiB. This may lead to unused capacity in the last extent and with many small Volumes, there will be a noticeable amount of unused storage.

One point, i do not know is : what does Storage Virtualize count? Written bytes : is this the number of occupied extents or the number of bytes written?

So numbers may differ from each other. You will have to pay attention to the usable Capacity, working with Thin Volumes on SVC AND FS5200

kind regards
Martin