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 Post subject: Reclaiming unused space from ESX datastores
PostPosted: Fri Jun 24, 2016 10:42 am 

Joined: Fri Jul 17, 2015 6:08 am
Posts: 30
Hi guys,

In the 'HP 3PAR StoreServ Storage and VMware vSphere 6 best practices' document, HP state 'Thin persistence can reclaim space in chunks of 128MB of contiguous unused or zero-filled space on the LD'.

In the VMware doc 'Using esxcli in vSphere 5.5 and 6.0 to reclaim VMFS deleted blocks on thin-provisioned LUNs (2057513)' VMware say 'The default value of 200 for the -n number or --reclaim-unit=number argument is appropriate in most environments, but some array vendors may suggest a larger or smaller value depending on how the array handles the SCSI UNMAP command'.

Are HP saying that the reclaim-unit argument should be 128 or is the default value of 200 still adequate?

Thanks.


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 Post subject: Re: Reclaiming unused space from ESX datastores
PostPosted: Wed Jun 29, 2016 2:01 pm 

Joined: Wed Jun 29, 2016 11:20 am
Posts: 17
My understanding is:
Vmware sends the unmap command on 200MB chunks. This is a convenient number, and nothing in HPE's documentation countermands this as far as I can tell. This space is returned to the volume directly, leading to the disparity between reserved and used space.

In the background, completely outside of your control, the array may return logical disks to the CPG. This space is then available for any volume attached to the CPG, and can be freed to the completely free pool by running a compactcpg. Unfortunately, it is entirely possible for terabytes of space to stay attached in the reserved but unused state for at least 6 months (still counting on mine!), and there's nothing you can do about it aside from migrating off that volume and deleting it.


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 Post subject: Re: Reclaiming unused space from ESX datastores
PostPosted: Thu Jun 30, 2016 4:34 am 

Joined: Fri Jul 17, 2015 6:08 am
Posts: 30
I don't think it's acceptable that we should have to wait more than a few weeks for unused space to be released back to the system. HP are selling the zero detect feature with the "start thin, get thin stay thin" sales pitch.

I've raised this via support. I would expect to see at least 100GB per day to be released back to the system. It's just been raised to L2, so will have to see what they say.


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 Post subject: Re: Reclaiming unused space from ESX datastores
PostPosted: Thu Jun 30, 2016 6:25 am 

Joined: Mon Sep 21, 2015 2:11 pm
Posts: 1191
Location: Europe
What type of 3PAR you got?

My experience is that this seems to be somewhat resource based. On 7200s, things take time. Some improvement on the 7200c, but generally 7400 and above tend to reclaim faster. 3PAR OS 3.1.2 was also painfully slow no matter what, 3.2.1 seems better. No experience with 3.1.3 or 3.2.2.

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 Post subject: Re: Reclaiming unused space from ESX datastores
PostPosted: Thu Jun 30, 2016 6:47 am 

Joined: Fri Jul 17, 2015 6:08 am
Posts: 30
They're 7200s running 3.2.1 MU2.

Hopefully support will be able to advise us on how this space can be reclaimed quicker.


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 Post subject: Re: Reclaiming unused space from ESX datastores
PostPosted: Thu Jun 30, 2016 8:34 am 

Joined: Wed Jun 29, 2016 11:20 am
Posts: 17
I have a 4-node 7400 which was on 3.2.1 MU2, and is now on 3.2.2 EMU2. I logged the same ticket about 6 months ago now. There's no way to accelerate it, it's done based on how busy the LUN is. The only way to view its progress is from CLI to run showeventlog -oneline -debug -min (how far back you want to go) -msg reclaim, and if you're on 3.2.2 you'll want to add -type notification as in 3.2.2 they intro'd a log that just spams that there is space to be reclaimed.

That will show you which volumes are reclaiming space, SD2 is snapshot space, SD is actual user space. I have a volume that has had over a TB to be reclaimed for 6 months now. I've also got some volumes that have reclaimed a couple terabytes in the course of a few weeks to a month. 3.2.2 EMU2 doesn't appear to be accelerating the reclaim process unfortunately.


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 Post subject: Re: Reclaiming unused space from ESX datastores
PostPosted: Thu Jul 14, 2016 8:41 pm 

Joined: Mon Jul 29, 2013 9:01 pm
Posts: 62
My 2 x7400 sans are reclaiming reasonable amounts every 24 hour period.

But I do run compact cpg's tasks every night except our full backup window nights


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 Post subject: Re: Reclaiming unused space from ESX datastores
PostPosted: Wed Dec 02, 2020 9:31 am 

Joined: Wed Jun 29, 2016 11:20 am
Posts: 17
Primera has added a compactvv command to condense the VV immediately. I've been asking for this for 5 years... and I'm currently bugging product management to backport to 3PAR.


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 Post subject: Re: Reclaiming unused space from ESX datastores
PostPosted: Thu Dec 03, 2020 1:12 pm 

Joined: Sat Jan 07, 2017 3:50 am
Posts: 32
More info available on compactvv with Primera? Lets hope one can do compactvv when remote replication on vv is active :D


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