GNU bug report logs - #51787
GC takes more than 9 hours on berlin

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Message #82 received at 51787 <at> debbugs.gnu.org (full text, mbox):

From: Mathieu Othacehe <othacehe <at> gnu.org>
To: Ricardo Wurmus <rekado <at> elephly.net>
Cc: 51787 <at> debbugs.gnu.org
Subject: Re: Disk performance on ci.guix.gnu.org
Date: Mon, 20 Dec 2021 22:53:45 +0100

Hey,

> Do you mean time the copy or time the removal from that storage?  You
> know what, I’ll time both.  I’ll need to get more space first.  I think
> the trash directory is larger than the 500G that I got for testing the
> SAN.

Yeah I meant removal time :) I found this article[1] that suggests that
over time the ext4 fragmentation can cause a performance drop that is
very noticeable on hard drives.

I'm trying to determine how fragmented is the sdb1 file-system, by
running e4defrag and e2freefrag[2], but I'm not sure if they will
complete soon.

Copying and removing /gnu/store/trash on the SAN will be interesting but
the ultimate test would be to be able to re-create the ext4 file-system
directly on Berlin's sdb drive to evaluate the fragmentation role in
this funny business.

Thanks,

Mathieu

[1]: https://www.usenix.org/system/files/hotstorage19-paper-conway.pdf
[2]: https://cromwell-intl.com/open-source/performance-tuning/file-systems.html

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