understanding Compellent SC5020 utilization stats

Question

Hi, I am trying to understand different parameters in utilization stats, Could you please help me understand these in detail. we are using SC5020, trying to understand the utilization statistics. What is the difference between Allocated Space and Used Space , the help guide describes both as the same.    Configured Space — Total space of all configured volumes in the Storage Center. Available Space — Total capacity for all non-spare disks installed in the Storage Center. Storage Center 7.3 and later - Available Space is the total of Allocated Space plus Free Space. Storage Center 7.2 and earlier - Available Space is the total of Used Space plus Free Space. Free Space — Unused space for all Storage Types. Allocated Space — Space used by volume data, snapshots, and RAID overhead. Beginning with Storage Center 7.3, Allocated Space is also displayed as a percentage of Available Space. Used Space — Space used by volume data, snapshots, and RAID overhead. Prior to Storage Center 7.3, Used Space is also displayed as a percentage of Available Space. System Space — Space used for system administration. Storage Threshold Alert — Value, as a percentage of remaining space, when an alert is sent to indicate that disk space is getting low.

DELL-Sam L · Accepted Answer

Hello VNKR,

Allocated Space= Amount of disk space allocated on the disks for volumes plus RAID overhead.

Used Space= Amount of configured space used by the Storage Center plus RAID overhead.

Here is the link to the administrator guide and if you look on page 292 it explains all these fields. https://dell.to/3hAN0hf

Please let us know if you have any other questions.

Origin3k · Accepted Answer

@VNKR

for my understanding the system needs some (pre)allocated space to get its job done. The system moves data around within the RAID Tiering and also for the Dataprogression and maybe also for Dedup/Compression. Its also looks like a High Watermark or at least based on historical data and the allocated space usage isnt adjusted in realtime or when there is no need for.

If you take a look to storage types the system will tell you how much "free" space is within the allocated space and how much "virgin" space which is titled "Non Allocated".

For my Tier1 it means 5.77TB within allocated and 1.14 Non-Allocated which is in total 6.91TB.

Regards,
Joerg

Origin3k · Answer

Someone should add the information why the system allocated space at all and for what reason and how its managed by the system.   Regards,Joerg

VNKR · Answer

Thank you @DELL-Sam L . 7.4 admin guide has different explanation for used vs allocated. So it is sort of reservation on disk space, for the volumes that are created.

Sorry about few more questions,

Is this a dynamic reservation? or pre allocated capacity for specific volumes and will not be shared by the new volumes that would be created in the feature
What is max limit for allocated capacity ? is it equal to the available capacity.

I agree with @Origin3k , granular calculations with out the right explanation will confuse.

Thank you!!

VNKR · Answer

Thank you @Origin3k @DELL-Sam L  Got some insights and understanding

Compellent

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