From: "Benoît Canet" <benoit.canet@irqsave.net>
To: Kevin Wolf <kwolf@redhat.com>
Cc: "Benoît Canet" <benoit.canet@irqsave.net>,
qemu-devel@nongnu.org, "Stefan Hajnoczi" <stefanha@redhat.com>
Subject: Re: [Qemu-devel] [RFC V8 01/24] qcow2: Add journal specification.
Date: Wed, 3 Jul 2013 14:30:59 +0200 [thread overview]
Message-ID: <20130703123059.GA5482@irqsave.net> (raw)
In-Reply-To: <20130703080415.GA2784@dhcp-200-207.str.redhat.com>
> Care to explain that in more detail? Why shouldn't it work on spinning
> disks?
Hash are random they introduce random read access.
With a QCOW2 cluster size of 4KB the deduplication code when writting duplicated
data will do one random read per 4KB block to deduplicate.
A server grade hardisk is rated for 250 iops. This traduce in 1MB/s of deduplicated
data. Not very usable.
On the contrary a samsung 840 pro SSD is rated for 80k iops of random read.
That should traduce in 320MB/s of potentially deduplicated data.
Havind dedup metadata on SSD and actual data on disk would solve the problem but
it would need block backend.
Benoît
next prev parent reply other threads:[~2013-07-03 12:29 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-20 14:26 [Qemu-devel] [RFC V8 00/24] QCOW2 deduplication core functionality Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 01/24] qcow2: Add journal specification Benoît Canet
2013-07-02 14:42 ` Stefan Hajnoczi
2013-07-02 14:54 ` Kevin Wolf
2013-07-02 21:26 ` Benoît Canet
2013-07-03 8:08 ` Kevin Wolf
2013-07-03 7:51 ` Stefan Hajnoczi
2013-07-02 21:23 ` Benoît Canet
2013-07-03 8:01 ` Stefan Hajnoczi
2013-07-03 12:35 ` Benoît Canet
2013-07-03 8:04 ` Kevin Wolf
2013-07-03 12:30 ` Benoît Canet [this message]
2013-07-03 8:12 ` Stefan Hajnoczi
2013-07-03 12:53 ` Benoît Canet
2013-07-04 7:13 ` Stefan Hajnoczi
2013-07-04 10:01 ` Benoît Canet
2013-07-16 22:45 ` Benoît Canet
2013-07-17 8:20 ` Kevin Wolf
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 02/24] qcow2: Add deduplication structures and fields Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 03/24] qcow2: Add journal Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 04/24] qcow2: Create the log store Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 05/24] qcow2: Add the hash store Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 06/24] qcow2: Add the deduplication store Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 07/24] qcow2: Add qcow2_dedup_read_missing_and_concatenate Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 08/24] qcow2: Create a way to link to l2 tables when deduplicating Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 09/24] qcow2: Make qcow2_update_cluster_refcount public Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 10/24] qcow2: Add qcow2_dedup and related functions Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 11/24] qcow2: Add qcow2_dedup_store_new_hashes Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 12/24] qcow2: Do allocate on rewrite on the dedup case Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 13/24] qcow2: Implement qcow2_compute_cluster_hash Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 14/24] qcow2: Load and save deduplication table header extension Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 15/24] qcow2: Extract qcow2_set_incompat_feature and qcow2_clear_incompat_feature Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 16/24] block: Add qcow2_dedup format and image creation code Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 17/24] qcow2: Drop hash for a given cluster when dedup makes refcount > 2^16/2 Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 18/24] qcow2: Remove hash when cluster is deleted Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 19/24] qcow2: Integrate deduplication in qcow2_co_writev loop Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 20/24] qcow2: Serialize write requests when deduplication is activated Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 21/24] qcow2: Integrate SKEIN hash algorithm in deduplication Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 22/24] qcow2: Add qcow2_dedup_init and qcow2_dedup_close Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 23/24] qcow2: Enable the deduplication feature Benoît Canet
2013-06-20 14:26 ` [Qemu-devel] [RFC V8 24/24] qcow2: Enable deduplication tests Benoît Canet
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