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Re: [Qemu-devel] [RFC V4 00/30] QCOW2 deduplication
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [RFC V4 00/30] QCOW2 deduplication |
Date: |
Wed, 02 Jan 2013 11:01:04 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 |
On 01/02/2013 10:33 AM, Benoît Canet wrote:
>> How does this code handle hash collisions, and do you have some regression
>> tests that purposefully create a dedup hash collision, and verify that the
>> 'right thing' happens?
>
> The two hash function that can be used are cryptographics and not broken yet.
> So nobody knows how to generate a collision.
I can understand that it is hard to write a test for two distinct data
sectors hashing to the same value, but perhaps it's worth including a
debug-only hash algorithm that intentionally generates collisions, just
to prove that you handle them correctly. De-duplicating collided data,
while unlikely, is still a case of data loss that not everyone is happy
to risk.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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- [Qemu-devel] [RFC V4 12/30] qcow2: Load and save deduplication table header extension., (continued)
- [Qemu-devel] [RFC V4 12/30] qcow2: Load and save deduplication table header extension., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 16/30] qcow2: Extract qcow2_add_feature and qcow2_remove_feature., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 06/30] qcow2: Add qcow2_dedup and related functions, Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 26/30] qcow2: Add lazy refcounts to deduplication to prevent qcow2_cache_set_dependency loops, Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 18/30] qcow2: Behave correctly when refcount reach 0 or 2^16., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 11/30] qcow2: create function to load deduplication hashes at startup., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 13/30] qcow2: Extract qcow2_do_table_init., Benoît Canet, 2013/01/02
- Re: [Qemu-devel] [RFC V4 00/30] QCOW2 deduplication, Troy Benjegerdes, 2013/01/02
- Re: [Qemu-devel] [RFC V4 00/30] QCOW2 deduplication, Benoît Canet, 2013/01/02
- Re: [Qemu-devel] [RFC V4 00/30] QCOW2 deduplication, Troy Benjegerdes, 2013/01/02
- Re: [Qemu-devel] [RFC V4 00/30] QCOW2 deduplication, Benoît Canet, 2013/01/02
- Re: [Qemu-devel] [RFC V4 00/30] QCOW2 deduplication, ronnie sahlberg, 2013/01/02
- Re: [Qemu-devel] [RFC V4 00/30] QCOW2 deduplication, Benoît Canet, 2013/01/02
- Re: [Qemu-devel] [RFC V4 00/30] QCOW2 deduplication, Troy Benjegerdes, 2013/01/02
- Re: [Qemu-devel] [RFC V4 00/30] QCOW2 deduplication, ronnie sahlberg, 2013/01/02
- Re: [Qemu-devel] [RFC V4 00/30] QCOW2 deduplication, Stefan Hajnoczi, 2013/01/03
- Re: [Qemu-devel] [RFC V4 00/30] QCOW2 deduplication, Troy Benjegerdes, 2013/01/03
- Re: [Qemu-devel] [RFC V4 00/30] QCOW2 deduplication, Dietmar Maurer, 2013/01/04