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Re: [Qemu-devel] [PATCH v4 4/6] introduce new vma archive format
From: |
Dietmar Maurer |
Subject: |
Re: [Qemu-devel] [PATCH v4 4/6] introduce new vma archive format |
Date: |
Fri, 22 Feb 2013 13:52:15 +0000 |
> > For example, if you backup a file which mostly contains empty blocks,
> > you will duplicate the size of the resulting file!
>
> If describing an empty image takes more than a couple of bytes, you're doing
> something seriously wrong.
really?
> Because for that case it would be easy enough to
> have an entry that just says "0 GB - 2 GB" is zero, and that's it. 16 bytes
> for 2 GB
> of virtual disk size, sounds pretty good to me.
Zero region are distributed, not continuous, in most cases.
> And it would only be needed if VMAs support backing files, because for normal
> sparse blocks, I don't even see any reason why the VMA should contain any
> information about them. They are never written to, so they are by definition
> sparse.
We track zero regions at 4K level, and Cluster size is 64K.
So I normally just use 1bit to store information about empty blocks.
I thought that is quite good, but you obviously have a better idea?
- Re: [Qemu-devel] [PATCH v4 4/6] introduce new vma archive format, (continued)
- Re: [Qemu-devel] [PATCH v4 4/6] introduce new vma archive format, Dietmar Maurer, 2013/02/22
- Re: [Qemu-devel] [PATCH v4 4/6] introduce new vma archive format, Kevin Wolf, 2013/02/22
- Re: [Qemu-devel] [PATCH v4 4/6] introduce new vma archive format, Dietmar Maurer, 2013/02/22
- Re: [Qemu-devel] [PATCH v4 4/6] introduce new vma archive format, Kevin Wolf, 2013/02/22
- Re: [Qemu-devel] [PATCH v4 4/6] introduce new vma archive format, Dietmar Maurer, 2013/02/22
- Re: [Qemu-devel] [PATCH v4 4/6] introduce new vma archive format, Kevin Wolf, 2013/02/22
- Re: [Qemu-devel] [PATCH v4 4/6] introduce new vma archive format,
Dietmar Maurer <=
- Re: [Qemu-devel] [PATCH v4 4/6] introduce new vma archive format, Kevin Wolf, 2013/02/22
- Re: [Qemu-devel] [PATCH v4 4/6] introduce new vma archive format, Dietmar Maurer, 2013/02/22
- Re: [Qemu-devel] [PATCH v4 4/6] introduce new vma archive format, Dietmar Maurer, 2013/02/22
- Re: [Qemu-devel] [PATCH v4 4/6] introduce new vma archive format, Dietmar Maurer, 2013/02/22
- Re: [Qemu-devel] [PATCH v4 4/6] introduce new vma archive format, Dietmar Maurer, 2013/02/22
- Re: [Qemu-devel] [PATCH v4 4/6] introduce new vma archive format, Kevin Wolf, 2013/02/22
Re: [Qemu-devel] [PATCH v4 0/6] Efficient VM backup for qemu, Stefan Hajnoczi, 2013/02/20