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 Post subject: Garbage Collector
PostPosted: Sun Nov 12, 2017 11:02 pm 

Joined: Thu Nov 02, 2017 12:56 pm
Posts: 3
Does anyone have any knowledge of this process? I get that it is supposed to reclaim space, but what are you supposed to do when it stops doing its job? Seems to be the issue we are facing at the moment.


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 Post subject: Re: Garbage Collector
PostPosted: Tue Nov 14, 2017 6:39 am 

Joined: Wed May 07, 2014 10:29 am
Posts: 137
It is a magical mystery to me. I have given up.
Just wait a week after UNMAP for the process to finish.

AFAIK there is a hidden task running, I do not think it is user interactive.
If anyone from HPE or partners who actually know, feel free to share!

- Anders


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 Post subject: Re: Garbage Collector
PostPosted: Tue Nov 14, 2017 8:07 am 

Joined: Mon Sep 21, 2015 2:11 pm
Posts: 478
Just throwing it out there, contact 3PAR support?

I've yet to find anywhere I can see the status of the process. If my memory serves me right you can do this in CLI to check what it has done (if running) for the last 24 hours

showeventlog -debug -oneline -msg GC -min 1440


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 Post subject: Re: Garbage Collector
PostPosted: Tue Nov 14, 2017 4:13 pm 

Joined: Thu Nov 02, 2017 12:56 pm
Posts: 3
Thanks for the replies. I had a elevated case open with HP and it eventually made it to the engineer level, our 3par actually dropped down to 3GB free space! We are still waiting for an official RCA.


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 Post subject: Re: Garbage Collector
PostPosted: Sun Nov 26, 2017 10:38 am 

Joined: Fri Nov 24, 2017 4:35 am
Posts: 1
Have you got any answer from the support?
After unmapping the unused storage space I see very slow process of decreasing the reserved user space. And at the same the same time the result of the command compactcpg -dr shows nothing to compact which isn't understandable by me.

The only way I see to return unused space is to use command tunevv.
Am I right?


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 Post subject: Re: Garbage Collector
PostPosted: Sun Dec 10, 2017 9:30 pm 

Joined: Mon Jul 29, 2013 9:01 pm
Posts: 49
The garbage collection is a very slow process (in fact its capped)

How do I know this.....we had a 3par upgrade done by HP on one of our full SSD sans

They forgot to turn garbage collection back on......over the course of a few weeks we noticed it going down ....and logged calls.....it was not until I insisted that this started happening after the upgrade that an escalation engineer found this process off....Because its so slow...HP were forced to give us 4 SSD's for free or else our daily loads would have stopped the SAN in its tracks.

SSD's and garbage collection and using Dedupe on luns this use of space grows very quickly and needs to be reclaimed.

it took 3 to 4 weeks to get our space back...but we got to keep our new ssd's


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 Post subject: Re: Garbage Collector
PostPosted: Mon Dec 11, 2017 8:51 am 

Joined: Tue Dec 23, 2014 2:04 pm
Posts: 11
Scenario: After performing zeroing/unmapping of volumes, there is a large discrepancy between volume used space and volume reserved space so the released capacity is not available for other volumes and cannot be released/re-used in other CPG's.

Two ways to address this issue:

1) Wait for defrag to create contiguous space and release this capacity to the cpg (segments of 128MB - region stripe size). Defrag is a system internal process - there is no way to configure or influence it unless you have a root login. You can open a support case and they can configure defrag to run more frequently and in a more aggressive mode. They require to undo the settings afterwards despite no guarantee that it wont happen again and usually it still takes forever to release all the space as defrag takes one volume at a time and only limited segments of each volume for each run.

2) Volume conversion from thin -> thick and thick -> thin will defrag all the volume space and release it back to the cpg, this is usually faster than waiting for defrag + can be scripted. The downside is that it requires available space.

/Morten


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