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From: | Stefan Priebe - Profihost AG |
Subject: | Re: [Qemu-devel] scsi-hd with discard_granularity and unmap results in Aborted Commands |
Date: | Mon, 19 Nov 2012 10:59:48 +0100 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121028 Thunderbird/16.0.2 |
Am 19.11.2012 10:54, schrieb Paolo Bonzini:
Il 19/11/2012 10:36, Stefan Priebe - Profihost AG ha scritto:Hi Paolo, Am 19.11.2012 09:10, schrieb Paolo Bonzini:I'm sorry the discard requests aren't failing. Qemu / Block driver starts to cancel a bunch of requests.That is being done in the kernel (the guest, I think) because the UNMAPs are taking too long.That makes sense. RBD handles discards as buffered I/O. When i do an mkfs.xfs on a 30GB device i see around 900 pending discard requests. rbd finishes them all before reporting success. If it is correct that a 3.6.7 kernel sends as many discard requests i only the a solution in using unbuffered I/O for discards. Do you know what is the correct way?I think the correct fix is to serialize them in the kernel.
So you mean this is not a bug in rbd or qemu this is a general bug in the linux kernel since they implemented discard?
Greets, Stefan
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