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Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive

From: Avi Kivity
Subject: Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive
Date: Wed, 26 May 2010 18:13:17 +0300
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20100330 Fedora/3.0.4-1.fc12 Thunderbird/3.0.4

On 05/26/2010 04:50 PM, Anthony Liguori wrote:
In fact, btrfs is currently unusable for virt because O_SYNC writes inflate a guest write to a host write. by a huge factor (50x-100x). cache=writethrough is 100% unusable, cache=writeback is barely tolerable. As of 2.6.32, cache=volatile is probably required to get something resembling reasonable performance on btrfs.

Of course, we expect that btrfs will improve in time, but still it doesn't seem to be fsync friendly.

So you're suggesting that anyone who uses virt on btrfs should be prepared to deal with data corruption on host failure?


That sounds to me like btrfs isn't ready for real workloads.

The btrfs developers aren't saying anything different. But people still want to try it out (to wire up snapshotting to management, for example).

error compiling committee.c: too many arguments to function

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