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Re: [Qemu-devel] [PATCH v3 0/8] block: drive-backup live backup command
From: |
Dietmar Maurer |
Subject: |
Re: [Qemu-devel] [PATCH v3 0/8] block: drive-backup live backup command |
Date: |
Thu, 23 May 2013 08:11:42 +0000 |
> > I also consider it safer, because you make sure the data exists (using hash
> > keys
> like SHA1).
> >
> > I am unsure how you can check if a dirty bitmap contains errors, or is out
> > of
> date?
> >
> > Also, you can compare arbitrary Merkle trees, whereas a dirty bitmap is
> > always
> related to a single image.
> > (consider the user remove the latest backup from the backup target).
>
> One disadvantage of Merkle trees is that the client becomes stateful - the
> client
> needs to store its own Merkle tree and this requires fancier client-side code.
What 'client' do you talk about here?
But sure, the code gets more complex, and needs considerable amount of RAM
to store the hash keys .
> It is also more expensive to update hashes than a dirty bitmap. Not because
> you
> need to hash data but because a small write (e.g. 1 sector) requires that you
> read the surrounding sectors to recompute a hash for the cluster. Therefore
> you
> can expect worse guest I/O performance than with a dirty bitmap.
There is no need to update any hash - You only need to do that on backup - in
fact, all
those things can be done by the backup driver.
> I still think it's a cool idea. Making it work well will require a lot more
> effort than
> a dirty bitmap.
How do you re-generate a dirty bitmap after a server crash?
- Re: [Qemu-devel] [PATCH v3 0/8] block: drive-backup live backup command, (continued)
- Re: [Qemu-devel] [PATCH v3 0/8] block: drive-backup live backup command, Paolo Bonzini, 2013/05/20
- Re: [Qemu-devel] [PATCH v3 0/8] block: drive-backup live backup command, Stefan Hajnoczi, 2013/05/21
- Re: [Qemu-devel] [PATCH v3 0/8] block: drive-backup live backup command, Paolo Bonzini, 2013/05/21
- Re: [Qemu-devel] [PATCH v3 0/8] block: drive-backup live backup command, Stefan Hajnoczi, 2013/05/21
- Re: [Qemu-devel] [PATCH v3 0/8] block: drive-backup live backup command, Paolo Bonzini, 2013/05/21
- Re: [Qemu-devel] [PATCH v3 0/8] block: drive-backup live backup command, Dietmar Maurer, 2013/05/21
- Re: [Qemu-devel] [PATCH v3 0/8] block: drive-backup live backup command, Stefan Hajnoczi, 2013/05/22
- Re: [Qemu-devel] [PATCH v3 0/8] block: drive-backup live backup command, Dietmar Maurer, 2013/05/22
- Re: [Qemu-devel] [PATCH v3 0/8] block: drive-backup live backup command, Dietmar Maurer, 2013/05/22
- Re: [Qemu-devel] [PATCH v3 0/8] block: drive-backup live backup command, Stefan Hajnoczi, 2013/05/23
- Re: [Qemu-devel] [PATCH v3 0/8] block: drive-backup live backup command,
Dietmar Maurer <=
- Re: [Qemu-devel] [PATCH v3 0/8] block: drive-backup live backup command, Stefan Hajnoczi, 2013/05/24
- Re: [Qemu-devel] [PATCH v3 0/8] block: drive-backup live backup command, Dietmar Maurer, 2013/05/24