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When running Data Domain Virtual Edition (DDVE) with the Active Tier on Object Store (ATOS), you must have virtual disks assigned to the DDVE to act as "local" metadata storage for the (remote) object data for backups as stored in the cloud provider bucket. Depending on the amount of data stored, the customer may have one or more virtual disks added to the DDVE as local metadata space, with the command "filesys show space tier active local-metadata" reporting on the total consumed, and use percentage for the combined local metadata space. However, some of the metrics shown by the command are not what the customer would expect, and may be confusing. For example, see the following disk allocation for a DDVE ATOS in Microsoft Azure: Disk Show Hardware ------------------ Disk Slot Manufacturer/Model Firmware Serial No. Capacity Type (pci/idx) ----- --------- ------------------------ -------- ---------- ---------- ---- dev1 0:0 Msft Virtual_Disk n/a (unknown) 250.0 GiB SAS dev2 1:0 Msft Virtual_Disk n/a (unknown) 400.0 GiB SAS dev3 3:0 Msft Virtual_Disk n/a (unknown) 10.0 GiB SAS dev4 3:1 Msft Virtual_Disk n/a (unknown) 1023.0 GiB SAS dev5 3:2 Msft Virtual_Disk n/a (unknown) 1023.0 GiB SAS dev6 3:3 Msft Virtual_Disk n/a (unknown) 1023.0 GiB SAS dev7 3:4 Msft Virtual_Disk n/a (unknown) 1023.0 GiB SAS dev8 3:5 Msft Virtual_Disk n/a (unknown) 1023.0 GiB SAS dev9 3:6 Msft Virtual_Disk n/a (unknown) 1023.0 GiB SAS dev10 3:7 Msft Virtual_Disk n/a (unknown) 1023.0 GiB SAS dev11 3:8 Msft Virtual_Disk n/a (unknown) 1023.0 GiB SAS dev12 3:9 Msft Virtual_Disk n/a (unknown) 1023.0 GiB SAS dev13 3:10 Msft Virtual_Disk n/a (unknown) 1023.0 GiB SAS dev14 3:11 Msft Virtual_Disk n/a (unknown) 1023.0 GiB SAS dev15 3:12 Msft Virtual_Disk n/a (unknown) 1023.0 GiB SAS dev16 3:13 Msft Virtual_Disk n/a (unknown) 1023.0 GiB SAS dev17 3:14 Msft Virtual_Disk n/a (unknown) 1023.0 GiB SAS ----- --------- ------------------------ -------- ---------- ---------- ---- Customer would expect the local metadata size to be 14 x 1024 GiB = 14 TiB, but the mentioned command reports this instead: Local MetaData Usage Stats -------------------------- Active Tier: local-metadata usage Size GiB Used GiB Avail GiB Use% -------- -------- --------- ----- 10459.7 6779.6 3680.1 65.0% -------- -------- --------- ----- Obviously, customer may be concerned of the several TiB of local metadata disk space which does not seem to be accounted for.
The output for the command and information printed in ASUPs is as designed, albeit a bit confusing to customers. "Local MetaData Usage Stats" reported size is only that for the file system Container SET (CSET) file in the local metadata tier. But metadata disks are being used for much more than just the FS CSET. The pool of storage used as metadata is dynamically allocated as needed to several FS components, so the reported size (which is only for the CSET) will not only be smaller (and sometimes, much smaller) than the raw metadata capacity (as the combined size of all disks used for metadata), but may also fluctuate (up and down) over time. Until a DDOS release is published with a more user-friendly output for the command, customers should rely on the "Use %" value, rather than on the GiB sizes reported. When the use percentage is high customers must add further disks to the DDVE metadata tier.
There is no change or workaround needed. Customers can continue to use the "filesys show space tier active local-metadata" command normally and rely on the command output "Use %" value as a means to keep track of effective utilization of the allocated local metadata disk space for the DDVE. Future DDOS releases may change the data output for the command so that it becomes more meaningful to customers.
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