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Re: [Qemu-devel] [PATCH] Add new block driver for the VDI format (use ai
From: |
Jamie Lokier |
Subject: |
Re: [Qemu-devel] [PATCH] Add new block driver for the VDI format (use aio) |
Date: |
Tue, 28 Jul 2009 09:34:52 +0100 |
User-agent: |
Mutt/1.5.13 (2006-08-11) |
Amit Shah wrote:
> On (Mon) Jul 27 2009 [10:23:19], Jamie Lokier wrote:
> > Kevin Wolf wrote:
> > > Though I guess that for static images typically not only metadata is
> > > preallocated, but zeros are written for the whole disk content? Maybe we
> > > could implement a three-way flag like preallocate=[no,metadata,data] and
> > > let qemu-img handle the data part (writing zeros is the same for all
> > > formats and would even work with raw).
> >
> > Note that you can also preallocate space with posix_fallocate(), which
> > fills the file with zeros but (sometimes) doesn't take as long as
> > writing zeros.
>
> It won't take as long as writing zeroes if the filesystem underneath has
> support for fallocate(). ext4, btrfs, xfs have support for fallocate().
>
> > Apparently it is almost essential when writing large files in small
> > pieces on Windows, and on Linux it is supported by the ext4
> > filesystem, but I haven't checked either claim.
>
> I did some comparisons:
>
> http://log.amitshah.net/2009/03/comparison-of-file-systems-and-speeding.html
>
> http://log.amitshah.net/2009/04/re-comparing-file-systems.html
There was some discussion of it on the rsync list, which is where I
learned it is important for NTFS performance on Windows.
By the way, why is fallocate() support being added to libvirt to
improve disk image creation, instead of to qemu-img?
-- Jamie
- Re: [Qemu-devel] [PATCH] RFC: Add new block driver for the VDI format, (continued)
- [Qemu-devel] [PATCH] RFC: Add new block driver for the VDI format (aio version), Stefan Weil, 2009/07/23
- [Qemu-devel] [PATCH] Check availability of uuid header / lib, Stefan Weil, 2009/07/23
- [Qemu-devel] [PATCH] Add new block driver for the VDI format (use aio), Stefan Weil, 2009/07/23
- Re: [Qemu-devel] [PATCH] Add new block driver for the VDI format (use aio), Kevin Wolf, 2009/07/24
- Re: [Qemu-devel] [PATCH] Add new block driver for the VDI format (use aio), Stefan Weil, 2009/07/24
- Re: [Qemu-devel] [PATCH] Add new block driver for the VDI format (use aio), Kevin Wolf, 2009/07/27
- Re: [Qemu-devel] [PATCH] Add new block driver for the VDI format (use aio), Jamie Lokier, 2009/07/27
- Re: [Qemu-devel] [PATCH] Add new block driver for the VDI format (use aio), Amit Shah, 2009/07/28
- Re: [Qemu-devel] [PATCH] Add new block driver for the VDI format (use aio),
Jamie Lokier <=
- Re: [Qemu-devel] [PATCH] Add new block driver for the VDI format (use aio), Daniel P. Berrange, 2009/07/28
- Re: [Qemu-devel] [PATCH] Add new block driver for the VDI format (use aio), Jamie Lokier, 2009/07/28
- Re: [Qemu-devel] [PATCH] Add new block driver for the VDI format (use aio), Kevin Wolf, 2009/07/28
- Re: [Qemu-devel] [PATCH] Add new block driver for the VDI format (use aio), Christoph Hellwig, 2009/07/31
- Re: [Qemu-devel] [PATCH] Add new block driver for the VDI format (use aio), Stefan Weil, 2009/07/31
- Re: [Qemu-devel] [PATCH] Add new block driver for the VDI format (use aio), Anthony Liguori, 2009/07/31
- Re: [Qemu-devel] [PATCH] Add new block driver for the VDI format (use aio), Stefan Weil, 2009/07/31
- [Qemu-devel] [PATCH] Add new block driver for the VDI format (only aio supported), Stefan Weil, 2009/07/31
[Qemu-devel] [PATCH] add support for new option of vdi format, Stefan Weil, 2009/07/23