From: Christoph Hellwig <hch@infradead.org>
To: Qu Wenruo <quwenruo.btrfs@gmx.com>
Cc: Christoph Hellwig <hch@infradead.org>,
dsterba@suse.cz, Qu Wenruo <wqu@suse.com>,
linux-btrfs@vger.kernel.org
Subject: Re: [PATCH DRAFT] btrfs: RAID56J journal on-disk format draft
Date: Wed, 25 May 2022 02:26:45 -0700 [thread overview]
Message-ID: <Yo32VXWO81PlccWH@infradead.org> (raw)
In-Reply-To: <bd6ac4d4-41bf-f662-e7c0-7841895554a6@gmx.com>
On Wed, May 25, 2022 at 05:13:11PM +0800, Qu Wenruo wrote:
> The problem is, we can have partial write for RAID56, no matter if we
> use NODATACOW or not.
>
> For example, we have a very typical 3 disks RAID5:
>
> 0 32K 64K
> Disk 1 |DDDDDDD| |
> Disk 2 |ddddddd|ddddddd|
> Disk 3 |PPPPPPP|PPPPPPP|
>
>
> D = old data, it's there for a while.
> d = new data, we want to write.
Oh. I keep forgetting that the striping is entirely on the physіcal
block basis and not logic block basis. Which makes the whole idea
of btrfs integrated raid5/6 not all that useful compared to just using
mdraid :(
next prev parent reply other threads:[~2022-05-25 9:27 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-24 6:13 [PATCH DRAFT] btrfs: RAID56J journal on-disk format draft Qu Wenruo
2022-05-24 11:08 ` kernel test robot
2022-05-24 12:19 ` kernel test robot
2022-05-24 17:02 ` David Sterba
2022-05-24 22:31 ` Qu Wenruo
2022-05-25 9:00 ` Christoph Hellwig
2022-05-25 9:13 ` Qu Wenruo
2022-05-25 9:26 ` Christoph Hellwig [this message]
2022-05-25 9:35 ` Qu Wenruo
2022-05-26 9:06 ` waxhead
2022-05-26 9:26 ` Qu Wenruo
2022-05-26 15:30 ` Goffredo Baroncelli
2022-05-26 16:10 ` David Sterba
2022-06-01 2:06 ` Wang Yugui
2022-06-01 2:13 ` Qu Wenruo
2022-06-01 2:25 ` Wang Yugui
2022-06-01 2:55 ` Qu Wenruo
2022-06-01 9:07 ` Wang Yugui
2022-06-01 9:27 ` Qu Wenruo
2022-06-01 9:56 ` Paul Jones
2022-06-01 10:12 ` Qu Wenruo
2022-06-01 18:49 ` Martin Raiber
2022-06-01 21:37 ` Qu Wenruo
2022-06-03 9:32 ` Lukas Straub
2022-06-03 9:59 ` Qu Wenruo
2022-06-06 8:16 ` Qu Wenruo
2022-06-06 11:21 ` Qu Wenruo
2022-06-06 18:10 ` Goffredo Baroncelli
2022-06-07 1:27 ` Qu Wenruo
2022-06-07 17:36 ` Goffredo Baroncelli
2022-06-07 22:14 ` Qu Wenruo
2022-06-08 17:26 ` Goffredo Baroncelli
2022-06-13 2:27 ` Qu Wenruo
2022-06-08 15:17 ` Lukas Straub
2022-06-08 17:32 ` Goffredo Baroncelli
2022-06-01 12:21 ` Qu Wenruo
2022-06-01 14:55 ` Robert Krig
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