From: "Theodore Y. Ts'o" <tytso-3s7WtUTddSA@public.gmane.org>
To: Mike Snitzer <snitzer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>,
"linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org"
<linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org>,
chengnt <chengnt-6jq1YtArVR3QT0dZR+AlfA@public.gmane.org>,
Dave Chinner <david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org>,
colyli <colyli-l3A5Bk7waGM@public.gmane.org>,
Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
"dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org"
<dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Mikulas Patocka
<mpatocka-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
"linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.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-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
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
WARNING: multiple messages have this Message-ID (diff)
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
WARNING: multiple messages have this Message-ID (diff)
From: "Theodore Y. Ts'o" <tytso@mit.edu>
To: Mike Snitzer <snitzer@redhat.com>
Cc: Huaisheng Ye <yehs2007@zoho.com>, Jan Kara <jack@suse.cz>,
yehs1 <yehs1@lenovo.com>,
"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
next prev parent reply other threads:[~2018-12-14 4:11 UTC|newest]
Thread overview: 83+ 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 16:07 ` Jan Kara
2018-08-27 16:07 ` Jan Kara
[not found] ` <20180827160744.GE4002-4I4JzKEfoa/jFM9bn6wA6Q@public.gmane.org>
2018-08-27 16:43 ` Kani, Toshi
2018-08-27 16:43 ` Kani, Toshi
2018-08-27 16:43 ` Kani, Toshi
[not found] ` <e38303902267d2d8bae8b0c88da84a4ed668e9fb.camel-ZPxbGqLxI0U@public.gmane.org>
2018-08-28 7:50 ` Jan Kara
2018-08-28 7:50 ` Jan Kara
2018-08-28 7:50 ` Jan Kara
[not found] ` <20180828075025.GA17756-4I4JzKEfoa/jFM9bn6wA6Q@public.gmane.org>
2018-08-28 17:56 ` Mike Snitzer
2018-08-28 17:56 ` Mike Snitzer
2018-08-28 17:56 ` Mike Snitzer
[not found] ` <20180828175630.GA1197-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-08-28 22:38 ` Kani, Toshi
2018-08-28 22:38 ` Kani, Toshi
2018-08-28 22:38 ` Kani, Toshi
2018-08-30 9:30 ` Jan Kara
2018-08-30 9:30 ` Jan Kara
2018-08-30 9:30 ` Jan Kara
[not found] ` <20180830093028.GC1767-4I4JzKEfoa/jFM9bn6wA6Q@public.gmane.org>
2018-08-30 18:49 ` Mike Snitzer
2018-08-30 18:49 ` Mike Snitzer
2018-08-30 18:49 ` Mike Snitzer
[not found] ` <20180830184907.GA14867-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-08-30 19:32 ` Jeff Moyer
2018-08-30 19:32 ` Jeff Moyer
2018-08-30 19:32 ` Jeff Moyer
[not found] ` <x494lfbabwi.fsf-RRHT56Q3PSP4kTEheFKJxxDDeQx5vsVwAInAS/Ez/D0@public.gmane.org>
2018-08-30 19:47 ` Mikulas Patocka
2018-08-30 19:47 ` Mikulas Patocka
2018-08-30 19:47 ` Mikulas Patocka
[not found] ` <alpine.LRH.2.02.1808301545200.30950-Hpncn10jQN4oNljnaZt3ZvA+iT7yCHsGwRM8/txMwJMAicBL8TP8PQ@public.gmane.org>
2018-08-30 19:53 ` Jeff Moyer
2018-08-30 19:53 ` Jeff Moyer
2018-08-30 19:53 ` Jeff Moyer
2018-08-30 23:38 ` Dave Chinner
2018-08-30 23:38 ` Dave Chinner
2018-08-30 23:38 ` Dave Chinner
2018-08-31 9:42 ` Jan Kara
2018-08-31 9:42 ` Jan Kara
2018-08-31 9:42 ` Jan Kara
2018-09-05 1:25 ` Dave Chinner
2018-09-05 1:25 ` Dave Chinner
2018-09-05 1:25 ` Dave Chinner
[not found] ` <20180831094255.GB11622-4I4JzKEfoa/jFM9bn6wA6Q@public.gmane.org>
2018-12-12 16:11 ` Huaisheng Ye
2018-12-12 16:11 ` Huaisheng Ye
2018-12-12 16:11 ` Huaisheng Ye
[not found] ` <167a3303a01.11a848ab768799.5161498967766415143-ytc+IHgoah0@public.gmane.org>
2018-12-12 16:12 ` Christoph Hellwig
2018-12-12 16:12 ` Christoph Hellwig
2018-12-12 16:12 ` Christoph Hellwig
[not found] ` <20181212161254.GA20790-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2018-12-12 17:50 ` Mike Snitzer
2018-12-12 17:50 ` Mike Snitzer
2018-12-12 17:50 ` Mike Snitzer
[not found] ` <20181212175047.GA24962-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-12-12 19:49 ` Kani, Toshi
2018-12-12 19:49 ` Kani, Toshi
2018-12-12 19:49 ` Kani, Toshi
2018-12-12 21:15 ` Theodore Y. Ts'o
2018-12-12 21:15 ` Theodore Y. Ts'o
[not found] ` <20181212211547.GA24926-AKGzg7BKzIDYtjvyW6yDsg@public.gmane.org>
2018-12-12 22:43 ` Mike Snitzer
2018-12-12 22:43 ` Mike Snitzer
2018-12-12 22:43 ` Mike Snitzer
[not found] ` <20181212224321.GA2902-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-12-14 4:11 ` Theodore Y. Ts'o [this message]
2018-12-14 4:11 ` [dm-devel] " Theodore Y. Ts'o
2018-12-14 4:11 ` Theodore Y. Ts'o
2018-12-14 8:24 ` [External] " Huaisheng HS1 Ye
2018-12-14 8:24 ` Huaisheng HS1 Ye
2018-12-14 8:24 ` Huaisheng HS1 Ye
[not found] ` <HK2PR03MB441871946735DE9EE714D10B92A10-LG58XzHXFHCi7fCZ8j4jr682SN/2zMuYvxpqHgZTriW3zl9H0oFU5g@public.gmane.org>
2018-12-18 19:49 ` Mike Snitzer
2018-12-18 19:49 ` Mike Snitzer
2018-12-18 19:49 ` Mike Snitzer
2018-08-30 19:44 ` Mikulas Patocka
2018-08-30 19:44 ` Mikulas Patocka
2018-08-30 19:44 ` Mikulas Patocka
[not found] ` <alpine.LRH.2.02.1808301537420.30950-Hpncn10jQN4oNljnaZt3ZvA+iT7yCHsGwRM8/txMwJMAicBL8TP8PQ@public.gmane.org>
2018-08-31 10:01 ` Jan Kara
2018-08-31 10:01 ` Jan Kara
2018-08-31 10:01 ` Jan Kara
2018-08-30 22:55 ` Dave Chinner
2018-08-30 22:55 ` Dave Chinner
2018-08-30 22:55 ` Dave Chinner
2018-08-31 9:54 ` Jan Kara
2018-08-31 9:54 ` Jan Kara
2018-08-31 9:54 ` Jan Kara
2018-08-30 19:17 ` [dm-devel] " Jeff Moyer
2018-08-30 19:17 ` Jeff Moyer
2018-08-30 19:17 ` Jeff Moyer
[not found] ` <x498t4naclf.fsf-RRHT56Q3PSP4kTEheFKJxxDDeQx5vsVwAInAS/Ez/D0@public.gmane.org>
2018-08-31 9:14 ` Jan Kara
2018-08-31 9:14 ` Jan Kara
2018-08-31 9:14 ` Jan Kara
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