Storage Space Question

Question

I feel really dumb asking this, but I'm expanding space out for the first time and don't want to mess things up - I've heard shrinking volumes can be messy, so I want to get this right the first go around.

I've attached a screenshot, but in case it doesn't show, we've got 71 TB of configured space between our volumes, and 132.19 TB of usable space.

If free space is including unused space in the configured volumes (not sure if that's correct), then I would think the amount of space I'm able to divide between my volumes would be 132.19 TB - 71 TB = 61.19 TB

Is that correct? Let me know if you need more info.

Origin3k · Accepted Answer

Yes your math is correct
Yes you can divide 61.19TB between your volumes

but... you have ask the wrong question or in case of a Compellent its some kind of unnecessary question because:

You are also able to divide 100TB, 200TB, $Whateveryouwant to your volumes as long you stay below some system limits, the Compellent wouldnt care
Your Servers will not able to storing 61.19TB of data (most likely) onto the SC

This is not a dumb question and after 10 years of selling and implementing Compellents your are in the same boat as most of (my) customers
Customers forget (i dont say that they never have understood how the system works) how a SC works in general and the GUI doesnt make it always easy to understand.

Your system

Create always thin provisioning volumes (possibilty to create prealocated volumes was added later and even than its not a default setting). So what ever you present as storage to your servers the Compellent dont allocate resources for ... until the servers starts writing
You can choose between different storage profiles which ends in different kind of RAIDs which have of course different space requirements/efficiency
Depending of the existing number of disks the systems support different sizes of Diskgroups (5/6 and 9/10). A larger group have better efficiency
Depending of the choice between single or double redundancy your RAID levels can vary
Depending of the fill ratio of your disks the amount of space needs for the distributed hotspare can vary because there is no fix dedicated hotspare disk anymore
Of course there is SCSI UNMAP
You can configure snapshots and the space which needs there depending of the daily change ratio of your and the configured blocksize of the Compellent
Than there is Data reduction as Compression/Dedup which is a post process so you can only the results later

So when someone ask how much space we have left on the system the answer will not match the assumption that we can store that amount of user data onto.

Regards,
Joerg

Compellent

Storage Space Question

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