From: "Theodore Y. Ts'o" <tytso@mit.edu>
To: Mike Snitzer <snitzer@redhat.com>
Cc: Jan Kara <jack@suse.cz>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
chengnt <chengnt@lenovo.com>, Dave Chinner <david@fromorbit.com>,
colyli <colyli@suse.de>, Christoph Hellwig <hch@infradead.org>,
"dm-devel@redhat.com" <dm-devel@redhat.com>,
Mikulas Patocka <mpatocka@redhat.com>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
Subject: Re: [dm-devel] Snapshot target and DAX-capable devices
Date: Thu, 13 Dec 2018 23:11:18 -0500 [thread overview]
Message-ID: <20181214041118.GE20880@thunk.org> (raw)
In-Reply-To: <20181212224321.GA2902@redhat.com>
On Wed, Dec 12, 2018 at 05:43:22PM -0500, Mike Snitzer wrote:
> > I would expect that dm-snapshot will be used quite a lot for
> > short-lived snapshots (that only live during a database backup or an
> > fsck run). I would hardly call that a "niche use case".
>
> dm-snapshot is only ~60% performant for 1 snapshot. Try to do
> additional snapshots and performance crawls to a stop (though I haven't
> reassessed performance in a while).
>
> dm-snapshot has been in Linux since before 2005, I don't know of all the
> users of it -- maybe there are a ton of users who only take a single
> temporary snapshot and we're all oblivious.
Well, here's one user:
https://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git/tree/scrub/e2scrub.in
This is a spiffed up version of my original script:
https://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git/tree/contrib/e2croncheck
I suppose we should look into enhancing e2scrub so it can deal with
volumes stored on dm-thin pools.....
> dm-thinp has the concept of an "external origin". Changes to origin LVM
> volume get copied out to the thin-pool (same copy cost as old
> dm-snapshot). But IIRC from that point on your LVM volume is a dm-thin
> device.
I would think the *snapshot* would have to be the dm-thin device, not
the origin volume, correct?
The original LVM module would still be mounted through the original
LVM device-mapper device, so it couldn't get transmogrified to be a
dm-thin device, right?
- Ted
_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm
next prev parent reply other threads:[~2018-12-14 4:11 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-27 16:07 Snapshot target and DAX-capable devices Jan Kara
2018-08-27 16:43 ` Kani, Toshi
2018-08-28 7:50 ` Jan Kara
2018-08-28 17:56 ` Mike Snitzer
2018-08-28 22:38 ` Kani, Toshi
2018-08-30 9:30 ` Jan Kara
2018-08-30 18:49 ` Mike Snitzer
2018-08-30 19:32 ` Jeff Moyer
2018-08-30 19:47 ` Mikulas Patocka
2018-08-30 19:53 ` Jeff Moyer
2018-08-30 23:38 ` Dave Chinner
2018-08-31 9:42 ` Jan Kara
2018-09-05 1:25 ` Dave Chinner
2018-12-12 16:11 ` Huaisheng Ye
2018-12-12 16:12 ` Christoph Hellwig
2018-12-12 17:50 ` Mike Snitzer
2018-12-12 19:49 ` Kani, Toshi
2018-12-12 21:15 ` Theodore Y. Ts'o
2018-12-12 22:43 ` Mike Snitzer
2018-12-14 4:11 ` Theodore Y. Ts'o [this message]
2018-12-14 8:24 ` [External] " Huaisheng HS1 Ye
2018-12-18 19:49 ` Mike Snitzer
2018-08-30 19:44 ` Mikulas Patocka
2018-08-31 10:01 ` Jan Kara
2018-08-30 22:55 ` Dave Chinner
2018-08-31 9:54 ` Jan Kara
2018-08-30 19:17 ` [dm-devel] " Jeff Moyer
2018-08-31 9:14 ` Jan Kara
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=20181214041118.GE20880@thunk.org \
--to=tytso@mit.edu \
--cc=chengnt@lenovo.com \
--cc=colyli@suse.de \
--cc=david@fromorbit.com \
--cc=dm-devel@redhat.com \
--cc=hch@infradead.org \
--cc=jack@suse.cz \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-nvdimm@lists.01.org \
--cc=mpatocka@redhat.com \
--cc=snitzer@redhat.com \
/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;
as well as URLs for NNTP newsgroup(s).