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Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format
From: |
Christoph Hellwig |
Subject: |
Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format |
Date: |
Fri, 10 Sep 2010 15:48:59 +0200 |
User-agent: |
Mutt/1.3.28i |
On Fri, Sep 10, 2010 at 08:22:14AM -0500, Anthony Liguori wrote:
> fsck will always be fast on qed because the metadata is small. For a
> 1PB image, there's 128MB worth of L2s if it's fully allocated (keeping
> in mind, that once you're fully allocated, you'll never fsck again). If
> you've got 1PB worth of storage, I'm fairly sure you're going to be able
> to do 128MB of reads in a short period of time. Even if it's a few
> seconds, it only occurs on power failure so it's pretty reasonable.
I don't think it is. Even if the metadata is small it can still be
spread all over the disks and seek latencies might kill you. I think
if we want to make qed future proof it needs to provide transactional
integrity for metadata updates, just like a journaling filesystem.
Given that small amount of metadata and less different kinds it will
still be a lot simpler than a full filesystem of course.
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, (continued)
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Anthony Liguori, 2010/09/09
- [Qemu-devel] Re: [RFC] qed: Add QEMU Enhanced Disk format, Paolo Bonzini, 2010/09/09
- [Qemu-devel] Re: [RFC] qed: Add QEMU Enhanced Disk format, Anthony Liguori, 2010/09/09
- Re: [Qemu-devel] Re: [RFC] qed: Add QEMU Enhanced Disk format, Christoph Hellwig, 2010/09/09
- [Qemu-devel] Re: [RFC] qed: Add QEMU Enhanced Disk format, Avi Kivity, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Avi Kivity, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Avi Kivity, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Stefan Hajnoczi, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Avi Kivity, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Anthony Liguori, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format,
Christoph Hellwig <=
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Anthony Liguori, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Kevin Wolf, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Anthony Liguori, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Kevin Wolf, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Anthony Liguori, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Kevin Wolf, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Miguel Di Ciurcio Filho, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Avi Kivity, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Christoph Hellwig, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Avi Kivity, 2010/09/10