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[Qemu-devel] Re: Notes on block I/O data integrity
From: |
Rusty Russell |
Subject: |
[Qemu-devel] Re: Notes on block I/O data integrity |
Date: |
Thu, 27 Aug 2009 20:21:55 +0930 |
User-agent: |
KMail/1.11.2 (Linux/2.6.28-15-generic; KDE/4.2.2; i686; ; ) |
On Wed, 26 Aug 2009 03:41:20 am Christoph Hellwig wrote:
> As various people wanted to know how the various data integrity patches
> I've send out recently play together here's a small writeup on what
> issues we have in QEMU and how to fix it:
Classic mail. Thanks for the massive and coherent clue injection!
> Action plan for the guest drivers:
>
> - virtio-blk needs to advertise ordered queue by default.
> This makes cache=writethrough safe on virtio.
From a guest POV, that's "we don't know, let's say we're ordered because that
may make us safer". Of course, it may not help: how much does it cost to
drain the queue?
The bug, IMHO is that we *should* know. And in future I'd like to fix that,
either by adding an VIRTIO_BLK_F_ORDERED feature, or a VIRTIO_BLK_F_UNORDERED
feature.
> Action plan for QEMU:
>
> - IDE needs to set the write cache enabled bit
> - virtio needs to implement a cache flush command and advertise it
> (also needs a small change to the host driver)
So, virtio-blk needs to be enhanced for this as well.
Thanks!
Rusty.
[Qemu-devel] Re: Notes on block I/O data integrity, Nikola Ciprich, 2009/08/25
[Qemu-devel] Re: Notes on block I/O data integrity,
Rusty Russell <=
Re: [Qemu-devel] Notes on block I/O data integrity, Jamie Lokier, 2009/08/27