Hello everyone, a few capacity usage questions on the system described below;

- FS9500 with FCM3 drives, Compression Accelerator cards installed and a single Non DRP storage pool.

- All  vdisks are "fully allocated", ie created without specifying compression or Thin-provisioning.

1. From the dashboard, I see compression savings and thin savings, Am I correct to assume this is entirely from the FCM compression feature running, regardless of which options were chosen during the vdisk creation?

2. I would like confirmation on the output of the capacity savings report (comprestimator).  Are the compression, thin and total savings reported actual savings or potential ?

3/ Looking at GUI reported pool capacity , what is the difference between usable capacity and capacity details and which value should be monitored for threshold breaches ?

    Current values on this pool respectively.

    188.50 TiB / 505.52 TiB (37%)        546.06 TiB / 1.48 PiB (36%)            Available usable capacity:316.83 TiB

4. Are compression cards only utilized if DRP pools are present.?

5. Is there any benefit to creating compression enable vdisks in a DRP pool if FCM is already doing compression by default ?

Thank You.

1. "Yes" per your configuration.
2. You actually do not need the IBM FlashSystem comprestimator command for that purpose. There are analyzevdisk and analyzevdiskbysystem commands available and their corresponding GUI operation on the system.
3. You should monitor the usable capacity.
4. Yes, I would set some alerts on it by specifying lower percentage values, say 55, 65, 75, and 85 on your IBM Storage Insights instance, if it is available.
5. I do not think of it unless you are going to use the deduplication volumes which are also DRP compressed at the same time.

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Keigo Matsubara, Storage Solution CTS, IBM Japan
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Some minor corrections above what the excellent Keigo Matsubara has already stated:

2 - analyzevdisk does on board what compresstimator did - it will tell you the sampled data compression ratio.  It runs automatically every 24ish hours and the output is generally useful to see for capacity planning.  I would also HIGHLY recommend looking at the capacity dashboards in SI, they are getting very very sophisticated and have excellent reporting generally.

3- Usable capacity == Physical capacity - in the case of fully allocated on FCMs, this will be the NAND cells capacity.
  Capacity Details - this is the logical capacity, sometimes called effective or addressable capacity.  you should ALSO Monitor this as standard pools will not reclaim capacity from unmaps and if you have a VERY VERY compressible data, you may run out of addressable space before you run out of physical capacity.

4- The on board compression cards are only utilized IF Data reduction volumes are created.  We use this hardware offload for compression and deduplication SHA hashing at this point in time.

5- We answer this in our Storage FAQs here: https://www.ibm.com/downloads/cas/9OGKVW2R (if that link doesn't work go to IBM Storage FlashSystem Resources | IBM  and look at the bottom of the page for the FAQs and then look at slide 18 and there abouts)

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Evelyn Perez
IBM Senior Technical Staff Member
IBM Storage Virtualize Software Architect for SVC and FlashSystem
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    Current values on this pool respectively.

    188.50 TiB / 505.52 TiB (37%)      - Actual capacity without consideration of any compression

  546.06 TiB / 1.48 PiB (36%)           - Capacity with compression (3:1, which you're almost getting, this can change if non-compressible data is added to the storage)

Available usable capacity:316.83 TiB - Actual capacity available for consumption without any compression benefit, can change based on the data inserted since the storage will compress data by default.

Hope this helps.