From: Rusty Russell <rusty@rustcorp.com.au> To: Christoph Hellwig <hch@lst.de> Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org Subject: Re: Notes on block I/O data integrity Date: Thu, 27 Aug 2009 20:21:55 +0930 [thread overview] Message-ID: <200908272021.56219.rusty@rustcorp.com.au> (raw) In-Reply-To: <20090825181120.GA4863@lst.de> 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.
WARNING: multiple messages have this Message-ID (diff)
From: Rusty Russell <rusty@rustcorp.com.au> To: Christoph Hellwig <hch@lst.de> Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org Subject: [Qemu-devel] Re: Notes on block I/O data integrity Date: Thu, 27 Aug 2009 20:21:55 +0930 [thread overview] Message-ID: <200908272021.56219.rusty@rustcorp.com.au> (raw) In-Reply-To: <20090825181120.GA4863@lst.de> 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.
next prev parent reply other threads:[~2009-08-27 10:51 UTC|newest] Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top 2009-08-25 18:11 Notes on block I/O data integrity Christoph Hellwig 2009-08-25 18:11 ` [Qemu-devel] " Christoph Hellwig 2009-08-25 19:33 ` Javier Guerra 2009-08-25 19:33 ` [Qemu-devel] " Javier Guerra 2009-08-25 19:36 ` Christoph Hellwig 2009-08-25 19:36 ` [Qemu-devel] " Christoph Hellwig 2009-08-26 18:57 ` Jamie Lokier 2009-08-26 18:57 ` Jamie Lokier 2009-08-26 22:17 ` Christoph Hellwig 2009-08-26 22:17 ` Christoph Hellwig 2009-08-27 9:00 ` Jamie Lokier 2009-08-25 20:25 ` Nikola Ciprich 2009-08-25 20:25 ` [Qemu-devel] " Nikola Ciprich 2009-08-26 18:55 ` Jamie Lokier 2009-08-26 18:55 ` Jamie Lokier 2009-08-27 0:15 ` Christoph Hellwig 2009-08-27 0:15 ` [Qemu-devel] " Christoph Hellwig 2009-08-27 10:51 ` Rusty Russell [this message] 2009-08-27 10:51 ` Rusty Russell 2009-08-27 13:42 ` Christoph Hellwig 2009-08-27 13:42 ` [Qemu-devel] " Christoph Hellwig 2009-08-28 2:03 ` Rusty Russell 2009-08-28 2:03 ` [Qemu-devel] " Rusty Russell 2009-08-27 14:09 ` [Qemu-devel] " Jamie Lokier 2009-08-27 14:09 ` Jamie Lokier
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