HPE StoreVirtual Storage / LeftHand
cancel
Showing results for 
Search instead for 
Did you mean: 

Space Consumed By Snapshots?

Paul Hutchings
Super Advisor

Space Consumed By Snapshots?

I have a P4500 virtualisation SAN (14.4tb).

 

On it, amongst other volumes I have a pair of volumes for Exchange 2010, one for databases, one for logs.

 

The database volume is 500gb, the log volume is 100gb, both are full provisioned and both are network RAID 10.

 

My cluster utilization was running at 47%.  I took an application aware snapshot of the Exchange volumes and the utilization immediately jumped up to 55%.  I took another application aware snapshot right away and the utilization stayed at 55%.  I then deleted both snapshots and it dropped to the original 47%.  I took another snapshot and it climbed to 55%.

 

I'm not clear why this should be as I thought snapshots are thin provisioned so only consume space at the same rate as the volume grows, whilst this has obviously used 8% of the entire SAN capacity which under network RAID10 is around 450gb or so.

 

Thanks for any light you can shed.

11 REPLIES
bublik
Valued Contributor

Re: Space Consumed By Snapshots?

I agree with you that logically it should work like that but I can't seem to find anything in the documentation that talks about application-managed snapshots should be thin provisioned. Do you have a Thin volume that you can take a application-managed snapshot?

 

Paul Hutchings
Super Advisor

Re: Space Consumed By Snapshots?

Only a fully provisioned volume.  I could change it to thin if it would help.

 

As a bit of a side question, is there any performance difference between thin and fully provisioned volumes or is the difference simply allocation of space up-front?

Jitun
HPE Pro

Re: Space Consumed By Snapshots?

Hi Paul

Snapshots are Thin Provisioned.
You would not see any appreciable difference is performance between Full Provisioned and Thin Provisioned Volumes.
--------------------------------------------------------------
How to assign points? Click the KUDOS! star!
bublik
Valued Contributor

Re: Space Consumed By Snapshots?

Jitun,

I have ran the same test and not seeing that the snapshot is thin provisioned.

If I look at the property of a snapshot, yes, it says Thin. But when I take the application-managed snapshot it take exact same size out of my cluster as the size of the volume.

 

 

 

Paul Hutchings
Super Advisor

Re: Space Consumed By Snapshots?

Jitun, as said, it certainly appears that whilst the subsequent snapshots are thin provisioned, and they all state thin in the CMC, the initial snapshot seems to take up an equal amount of space to the volume being snapshotted.

 

There's no other way the utilisation of a 5tb cluster can go from 48% to 55% just by taking a snapshot and then drop back to 48% by deleting it.

Jitun
HPE Pro

Re: Space Consumed By Snapshots?

@bublik
Snapshots are thin Provisioned on the SAN.
When you want to take a Backup of the Volume, out of SAN, then it should be an exact copy of the volume at that point of time. Which is the total size of the Volume.

@Paul
Initial Snapshot would always be the Size of the Volume when it is taken (Thin Provisioned), subsequent Snapshots are thin provisioned and only contains the Differential (changes since the previous snapshot was created)

I can have a look on your setup, you know how to reach me.
--------------------------------------------------------------
How to assign points? Click the KUDOS! star!
Jitun
HPE Pro

Re: Space Consumed By Snapshots?

Paul Take the snspshot and then email me the Logs.

I will reply back with the answer.

 

--------------------------------------------------------------
How to assign points? Click the KUDOS! star!
Paul Hutchings
Super Advisor

Re: Space Consumed By Snapshots?


Jitun wrote:

Paul Take the snspshot and then email me the Logs.

I will reply back with the answer.

 


Will do John, be tomorrow when I'm in the office.  Do you want me to raise a ticket or just email them?

Jitun
HPE Pro

Re: Space Consumed By Snapshots?

Just email is fine.

--------------------------------------------------------------
How to assign points? Click the KUDOS! star!
mdegraaf
Occasional Contributor

Re: Space Consumed By Snapshots?

Hi,

 

I have a simmilar problem:

 

When I take a snapshot from a 1TB full provisioned volume (network raid 10 2-way) the size of the first snapshot is 1,5TB so the total usage becomes 3,5TB. If I delete all the snapshots and convert the volume to thin the total volume usage is 1,25TB when I then take the first snapshot the total volume usage stays 1,25TB.

See attachments

 

Can anyone explain this behavior?

 

Best regards,

 

Martin

Emilo
Trusted Contributor

Re: Space Consumed By Snapshots?

Go to CMC and run diagnostics on off the nodes.

Then goto the logs and save the file clientmgrbin.log or something like that???

Anyway post that here I I can a look.