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Re: [Qemu-devel] [RFC] Propose the Fast Virtual Disk (FVD) image format
From: |
Jamie Lokier |
Subject: |
Re: [Qemu-devel] [RFC] Propose the Fast Virtual Disk (FVD) image format that outperforms QCOW2 by 249% |
Date: |
Wed, 19 Jan 2011 01:12:12 +0000 |
User-agent: |
Mutt/1.5.13 (2006-08-11) |
Chunqiang Tang wrote:
> > Based on my limited understanding, I think FVD shares a
> > lot in common with the COW format (block/cow.c).
> >
> > But I think most of the advantages you mention could be considered as
> > additions to either qcow2 or qed. At any rate, the right way to have
> > that discussion is in the form of patches on the ML.
>
> FVD is much more advanced than block/cow.c. I would be happy to discuss
> possible leverage, but setting aside the details of QCOW2, QED, and FVD,
> let’s start with a discussion of what is needed for the next generation
> image format.
Thank you for the detailed description.
FVD looks quite good to me; it seems very simple yet performant at the
same time, due to its smart yet simple design.
> Moreover, using a host file system not only adds overhead, but
> also introduces data integrity issues. Specifically, if I/Os uses O_DSYNC,
> it may be too slow. If I/Os use O_DIRECT, it cannot guarantee data
> integrity in the event of a host crash. See
> http://lwn.net/Articles/348739/ .
You have the same issue with O_DIRECT when using a raw disk device
too. That is, O_DIRECT on a raw device does not guarantee integrity
in the event of a host crash either, for mostly the same reasons.
-- Jamie
- [Qemu-devel] [RFC] Propose the Fast Virtual Disk (FVD) image format that outperforms QCOW2 by 249%, Chunqiang Tang, 2011/01/04
- Re: [Qemu-devel] [RFC] Propose the Fast Virtual Disk (FVD) image format that outperforms QCOW2 by 249%, Christoph Hellwig, 2011/01/19
- Re: [Qemu-devel] [RFC] Propose the Fast Virtual Disk (FVD) image format that outperforms QCOW2 by 249%, Chunqiang Tang, 2011/01/19
- Re: [Qemu-devel] [RFC] Propose the Fast Virtual Disk (FVD) image format that outperforms QCOW2 by 249%, Christoph Hellwig, 2011/01/19
- Re: [Qemu-devel] [RFC] Propose the Fast Virtual Disk (FVD) image format that outperforms QCOW2 by 249%, Chunqiang Tang, 2011/01/19
- Re: [Qemu-devel] [RFC] Propose the Fast Virtual Disk (FVD) image format that outperforms QCOW2 by 249%, Christoph Hellwig, 2011/01/19
Re: [Qemu-devel] [RFC] Propose the Fast Virtual Disk (FVD) image format that outperforms QCOW2 by 249%, Stefan Hajnoczi, 2011/01/06