From: Efraim Flashner <efraim@flashner.co.il>
To: Maxim Cournoyer <maxim.cournoyer@gmail.com>
Cc: "Ludovic Courtès" <ludo@gnu.org>,
"Pierre Neidhardt" <mail@ambrevar.xyz>,
40236@debbugs.gnu.org,
"Jonathan Brielmaier" <jonathan.brielmaier@web.de>
Subject: [bug#40236] [PATCH] doc: Suggest Btrfs with compression instead of ext4 for root partition.
Date: Mon, 1 Jun 2020 09:16:03 +0300 [thread overview]
Message-ID: <20200601061603.GF7397@E5400> (raw)
In-Reply-To: <878sh75scf.fsf@gmail.com>
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> >
> > Two more things:
> > /var/guix/db should probably have CoW disabled, as should /tmp
>
> I haven't bothered and my system seems to be doing OK. When I asked in
> #btrfs, people told me to keep CoW unless I was really sure it was a
> problem (i.e., run benchmarks), as it implies loosing the checksum
> validation and compression. The command 'man 5 btrfs' also states that
> "Updates in-place improve performance for workloads that do frequent
> overwrites, at the cost of potential partial writes, in case the write
> is interrupted (system crash, device failure).", which doesn't sound
> safe to do for something as important as /var/guix/db.
Fair enough. I had heard that the CoW stuff wasn't great for databases.
I thought Leo ran into some issues with CoW on /tmp with the syncthing
tests.
> > would the deduplication of btrfs be "better" than the deduplication from
> > the daemon?
>
> On my system (with zstd compression), compsize -x /gnu/store suggests
> a resounding yes:
>
> --8<---------------cut here---------------start------------->8---
> sudo compsize -x /gnu/store
> Processed 3479664 files, 954748 regular extents (3002677 refs), 1451082 inline.
> Type Perc Disk Usage Uncompressed Referenced
> TOTAL 57% 51G 88G 217G
> none 100% 32G 32G 81G
> zstd 33% 18G 56G 135G
> --8<---------------cut here---------------end--------------->8---
>
> The delta between the Uncompressed and Referenced column is attributed
> to the deduplication done by Btrfs, and provides massive space savings
> in my case (this is just for /gnu/store).
>
> I'd need 217 GiB over a traditional fs such as EXT4 to hold my current
> store, while an uncompressed Btrfs partition would use only 88 GiB.
> With zstd compression, it's down to 51 GiB, or less that a quarter of
> what would have been required using EXT4.
I always understood that as with compression you're using 51G instead of
88G, and because of deduplication from the daemon it would only be 88G
instead of 217G. I took the numbers from 'none' to mean that the daemon
itself already did a lot of deduplication.
--
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next prev parent reply other threads:[~2020-06-01 6:17 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-26 8:35 [bug#40236] [PATCH] doc: Suggest Btrfs with compression instead of ext4 for root partition Pierre Neidhardt
2020-03-31 1:52 ` Maxim Cournoyer
2020-03-31 7:52 ` Pierre Neidhardt
2020-03-31 14:53 ` Pierre Neidhardt
2020-03-31 23:20 ` Maxim Cournoyer
2020-04-01 7:00 ` Pierre Neidhardt
2020-05-02 13:29 ` Pierre Neidhardt
2020-05-02 13:50 ` Marius Bakke
2020-05-02 13:58 ` Pierre Neidhardt
2020-05-02 19:03 ` Maxim Cournoyer
2020-05-03 7:01 ` Pierre Neidhardt
2020-05-04 15:22 ` Maxim Cournoyer
2020-04-01 21:28 ` Ludovic Courtès
2020-04-02 7:15 ` Pierre Neidhardt
2020-04-02 8:04 ` Ludovic Courtès
2020-04-02 10:36 ` Jonathan Brielmaier
2020-04-04 1:28 ` Maxim Cournoyer
2020-04-06 20:20 ` Pierre Neidhardt
2020-04-06 20:42 ` Jonathan Brielmaier
2020-04-07 7:07 ` Pierre Neidhardt
2020-04-08 3:18 ` Maxim Cournoyer
2020-04-09 20:12 ` Efraim Flashner
2020-04-10 7:39 ` Pierre Neidhardt
2020-04-10 8:24 ` Efraim Flashner
2020-04-10 9:04 ` Pierre Neidhardt
2020-04-14 2:20 ` Maxim Cournoyer
2020-04-14 6:53 ` Pierre Neidhardt
2020-05-31 7:39 ` Pierre Neidhardt
2020-05-31 7:55 ` Efraim Flashner
2020-06-01 4:21 ` Maxim Cournoyer
2020-06-01 6:16 ` Efraim Flashner [this message]
2020-06-01 7:48 ` Pierre Neidhardt
2020-06-01 18:29 ` Maxim Cournoyer
2020-05-31 21:07 ` Ludovic Courtès
2020-06-01 5:03 ` Maxim Cournoyer
2020-06-02 13:37 ` Pierre Neidhardt
2020-06-03 20:00 ` bug#40236: " Ludovic Courtès
2020-06-04 9:17 ` [bug#40236] " Pierre Neidhardt
2020-06-01 4:49 ` Maxim Cournoyer
2020-03-31 12:09 ` Jonathan Brielmaier
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