From: Stefan Hajnoczi <stefanha@redhat.com>
To: Dietmar Maurer <dietmar@proxmox.com>
Cc: Kevin Wolf <kwolf@redhat.com>,
Stefan Hajnoczi <stefanha@gmail.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
Markus Armbruster <armbru@redhat.com>
Subject: Re: [Qemu-devel] [RFC 0/8] block: Live backup prototype
Date: Mon, 11 Mar 2013 15:27:34 +0100 [thread overview]
Message-ID: <20130311142734.GA7611@stefanha-thinkpad.redhat.com> (raw)
In-Reply-To: <24E144B8C0207547AD09C467A8259F7557B30D69@lisa.maurer-it.com>
On Mon, Mar 11, 2013 at 09:26:26AM +0000, Dietmar Maurer wrote:
> > > > We track zero blocks at 4KB level to get small backup files. Restore
> > > > can handle those blocks differently, either pre-allocate or create
> > > > holes. That
> > > can even be a restore option.
> > >
> > > You are right, the behavior can be set at restore time.
> > >
> > > I'm curious how much of a win the 4 KB zero detection is on random
> > > Linux or Windows guest images. Have you collected numbers?
> >
> > Well, seems that it does not help much - it saves about 0.2% space. So maybe
> > we can remove that feature (and increase address space in the VMA format
> > instead).
>
> Sorry, I need to correct myself - I had a bug in the code.
>
> I can see space reduction up to 4% using this feature. Considering the fact that it
> comes at no cost, it would be stupid to remove it.
Okay, looks like it's useful but not a huge win.
In the NBD approach pipelining writes (or discards) ought to make 4 KB
zero blocks usable without overhead.
Stefan
next prev parent reply other threads:[~2013-03-11 14:27 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-09 22:22 [Qemu-devel] [RFC 0/8] block: Live backup prototype Stefan Hajnoczi
2013-03-09 22:22 ` [Qemu-devel] [RFC 1/8] block: add virtual_size to query-block QMP output Stefan Hajnoczi
2013-03-11 17:35 ` Eric Blake
2013-03-09 22:22 ` [Qemu-devel] [RFC 2/8] add basic backup support to block driver Stefan Hajnoczi
2013-03-09 22:22 ` [Qemu-devel] [RFC 3/8] backup: write to BlockDriverState instead of BackupDumpFunc Stefan Hajnoczi
2013-03-10 10:05 ` Dietmar Maurer
2013-03-10 11:13 ` Stefan Hajnoczi
2013-03-09 22:22 ` [Qemu-devel] [RFC 4/8] block: add block_backup QMP command Stefan Hajnoczi
2013-03-14 21:46 ` Eric Blake
2013-03-14 21:52 ` Eric Blake
2013-03-15 8:38 ` Stefan Hajnoczi
2013-04-11 12:32 ` Paolo Bonzini
2013-03-09 22:22 ` [Qemu-devel] [RFC 5/8] Add nbd server Python module Stefan Hajnoczi
2013-03-09 22:22 ` [Qemu-devel] [RFC 6/8] Add VMA backup archive writer " Stefan Hajnoczi
2013-03-09 22:22 ` [Qemu-devel] [RFC 7/8] Add vma-writer.py tool Stefan Hajnoczi
2013-03-09 22:22 ` [Qemu-devel] [RFC 8/8] Add backup.py tool Stefan Hajnoczi
2013-03-10 9:14 ` [Qemu-devel] [RFC 0/8] block: Live backup prototype Dietmar Maurer
2013-03-10 10:19 ` Stefan Hajnoczi
2013-03-10 10:38 ` Dietmar Maurer
2013-03-10 11:09 ` Stefan Hajnoczi
2013-03-10 10:50 ` Dietmar Maurer
2013-03-10 11:10 ` Stefan Hajnoczi
2013-03-11 8:58 ` Dietmar Maurer
2013-03-11 9:26 ` Dietmar Maurer
2013-03-11 14:27 ` Stefan Hajnoczi [this message]
2013-03-11 15:00 ` Dietmar Maurer
2013-03-11 17:11 ` Stefan Hajnoczi
2013-03-10 9:57 ` Dietmar Maurer
2013-03-10 10:41 ` Stefan Hajnoczi
2013-03-12 9:18 ` Kevin Wolf
2013-03-12 10:50 ` Stefan Hajnoczi
2013-03-12 11:15 ` Dietmar Maurer
2013-03-12 12:18 ` Stefan Hajnoczi
2013-03-12 11:22 ` Kevin Wolf
2013-03-12 11:31 ` Dietmar Maurer
2013-03-12 11:37 ` Dietmar Maurer
2013-03-12 12:17 ` Stefan Hajnoczi
-- strict thread matches above, loose matches on Subject: below --
2013-04-09 11:00 zhangleiqiang
2013-04-09 11:10 ` Stefan Hajnoczi
2013-04-09 15:34 ` Dietmar Maurer
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