From: Ronny Aasen <ronny+pve-user@aasen.cx>
To: pve-user@lists.proxmox.com
Subject: Re: [PVE-User] PBS : is dirty-bitmap really accurate ?
Date: Fri, 24 Jul 2020 09:54:13 +0200 [thread overview]
Message-ID: <acb18e3e-f8d8-64c3-aaaf-319d79668b39@aasen.cx> (raw)
In-Reply-To: <945247964.82475.1595574150577.JavaMail.zimbra@fws.fr>
On 24.07.2020 09:02, Daniel Berteaud wrote:
> ----- Le 23 Juil 20, à 23:59, Roland devzero@web.de a écrit :
>
>> i just had a look on that, too - i was backing up a VM i backed up this
>> afternoon,
>>
>> and for my curiosity 1GB out of 15GB was marked dirty.
>>
>> that looks a quite much for me for a mostly idle system, because there
>> was definitely only a little bit of change on the system within logfiles
>> in /var/log
>>
>> so i wonder what marked all that blocks dirty....
>>
>> i'm also suspecting atime changes...will keep an eye on that....
>
>
> It was my daily fstrim in my case. Each time you trim, it'll dirty all the blocks corresponding to unused space.
> I've switched this to a weekly job so bacups can run most of the time efficiently. Since then, dirty blocks went from ~15GB per VM on average to something betwwen 800MB and 4GB, which is much closer to what I expect, considering the 4MB granularity of the bitmap.
>
> I'll check on my biggest VM (Zabbix server) but I expect similar results
>
> Thanks Fabian and Jorge for pointing this out
>
> Cheers
> Daniel
>
would mounting the disk with discard help on this ? where it only trims
blocks that are actually discarded ? instead of touching the whole disk
with fstrim ?
Ronny
next prev parent reply other threads:[~2020-07-24 7:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-22 16:40 Daniel Berteaud
2020-07-23 6:43 ` Fabian Grünbichler
2020-07-23 6:53 ` Daniel Berteaud
2020-07-23 9:00 ` Jorge Boncompte
2020-07-23 9:34 ` Fabian Grünbichler
2020-07-23 9:40 ` Daniel Berteaud
2020-07-23 21:59 ` Roland
2020-07-24 7:02 ` Daniel Berteaud
2020-07-24 7:54 ` Ronny Aasen [this message]
2020-07-26 9:24 ` Mark Schouten
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