From: Roman Mamedov <rm@romanrm.net>
To: Graham Cobb <g.btrfs@cobb.uk.net>
Cc: Forza <forza@tnonline.net>,
Cedric.dewijs@eclipso.eu, linux-btrfs@vger.kernel.org
Subject: Re: synchronize btrfs snapshots over a unreliable, slow connection
Date: Tue, 5 Jan 2021 16:53:31 +0500 [thread overview]
Message-ID: <20210105165331.31aa8aee@natsu> (raw)
In-Reply-To: <cc104d7c-b993-941c-2851-9366a1d87902@cobb.uk.net>
On Tue, 5 Jan 2021 11:24:24 +0000
Graham Cobb <g.btrfs@cobb.uk.net> wrote:
> used that approach as the (old) NAS I was using had a very old linux
> version and didn't even run btrfs.
One anecdote --
I do use an old D-Link DNS-323 NAS with old kernel and distro (older Debian),
and only ~60 MB of RAM to serve a 8 TB disk or two. How does that even work?
Simple: it exports the disk(s) over the network as block devices via NBD, and
they are mounted remotely on a much more modern and powerful host.
A bit of a secret sauce surprisingly turned out to be the QEMU's NBD server
(qemu-nbd), it allows to set disk access modes inherited from QEMU itself, and
there with "--cache=none" the little thing doesn't choke (anymore) RAM-wise,
even with full jumbo-frames enabled on the network side.
(Other NBD servers were much less performant and/or reliable on the hardware).
Transfer speeds are around 17 MBytes/sec. That's on a Gbit LAN, and admittedly
running blockdevice-level access over a network does prefer to have a low ping
for good performance.
--
With respect,
Roman
next prev parent reply other threads:[~2021-01-05 11:54 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-04 20:51 synchronize btrfs snapshots over a unreliable, slow connection
2021-01-05 8:34 ` Forza
2021-01-05 11:24 ` Graham Cobb
2021-01-05 11:53 ` Roman Mamedov [this message]
2021-01-05 12:24 ` Cerem Cem ASLAN
2021-01-06 8:18 ` Forza
2021-01-07 2:06 ` Zygo Blaxell
2021-01-11 9:32 ` Cerem Cem ASLAN
2021-01-07 3:09 ` Zygo Blaxell
2021-01-07 19:22 ` Graham Cobb
2021-01-07 1:59 ` Zygo Blaxell
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210105165331.31aa8aee@natsu \
--to=rm@romanrm.net \
--cc=Cedric.dewijs@eclipso.eu \
--cc=forza@tnonline.net \
--cc=g.btrfs@cobb.uk.net \
--cc=linux-btrfs@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox