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MSA Space

 
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KingTony
Occasional Advisor

MSA Space

 

MSA.PNG

Hi, I have an MSA whose capacity is almost full, but i cant understand what the unallocated means, considering my uncommitted space is 0. KIndly clarify.

 

I got this explanation from a forum, but still cant understand the unallocated and allocated being more than the total of pool B

 

  1. For virtual storage: (With virtual you create a bunch of disks as a pool and all LUNs inside use all available disks on their LUN specific RAID level (just like the EVA / P6000 disk array did) - so as an example even a 2 disk mirror may use 10 disks - so it is much faster and the I/O does not hit only 2 disks while other disks are idle - more reliability, more performance.)

  • Allocated space is the amount of space that the data written to the pools takes.
    • Unallocated space is space that is designated for a pool but has not yet been allocated by a volume within that pool.
    • Uncommitted space is the overall space minus the allocated and unallocated space.
  1. For linear storage: ("linear" is the old style used by the G1 to G3 model already. You create a vdisk on a number of disks, let's say 5 disks for a RAID5 and create LUNs within. Then another vdisk ... and so on. The vdisks already set the RAID level for all LUNs inside.)

  • Allocated space is the space designated for all volumes. (When a linear volume is created, space equivalent to the
    volume size is reserved for it. This is not the case for virtual volumes.)
    • Unallocated space is the difference between the overall and allocated space.
Enterprise Engineer
3 REPLIES 3
Solution

Re: MSA Space

You need to understand two things Physical space and Logical space as this is Virtual Array

There are two Virtual Disk Group here Per Controller and each size 2400.5GB so total physical Capacity of the System = 4801.0GB

Pool A
---------

Virtual Disk Group Size = 2400.5GB
Reserved = 1203.6GB >>>>>>>>>>>>>>>>>This is for RAID parity and metadata
So Pool A actual usable Space = 1196.9GB

Actual data written and for that space actually got allocated from Pool or VDG = 1144.8GB

So actual physical space left in Pool A is 52.1GB

As I don't know how much is the provisioned size of the Volume so here actual calculation will be difficult but as per the picture I see Unallocated space is 101.2GB which means we have created volume of such size where 49.1GB overcommitted which means this much space actually not present under Pool A but we have told or committed that this is there so in the picture it says "A is overcommitted by 49.2GB"

So unallocated space is space that is designated for a pool but has not yet been allocated by a volume within that pool. Provisioned space which we have told at the time of volume creation that this volume will be of this size eventhough we don't know at the backend or physically that much space available or not. This is nothing but Thin provisioned volume.

Sameway you can calculate Pool B as well.

Let me know if you still have doubt on this.


Hope this helps!
Regards
Subhajit

If you feel this was helpful please click the KUDOS! thumb below!

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KingTony
Occasional Advisor

Re: MSA Space

Thanks Subhajit. I actually now get the idea. The actual space I have would also mean it's the unallocated space minus the overcommitted?

Enterprise Engineer

Re: MSA Space

Yes your understanding is correct.

Kindly mark the forum as resolved so that others can get the update as well who are all following this.

 

Hope this helps!
Regards
Subhajit

If you feel this was helpful please click the KUDOS! thumb below!

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