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From: Forza <forza@tnonline.net>
To: Qu Wenruo <wqu@suse.com>, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 0/4] btrfs: cleanups and preparation for the incoming RAID56J features
Date: Fri, 13 May 2022 17:14:21 +0200 (GMT+02:00)	[thread overview]
Message-ID: <b49e00b.dcea448a.180bdfc2a51@tnonline.net> (raw)
In-Reply-To: <cover.1652428644.git.wqu@suse.com>

Hi, 

---- From: Qu Wenruo <wqu@suse.com> -- Sent: 2022-05-13 - 10:34 ----

> Since I'm going to introduce two new chunk profiles, RAID5J and RAID6J
> (J for journal), 

Great to see work being done on the RAID56 parts of Btrfs. :) 

I am just a user of btrfs and don't have the full understanding of the internals, but it makes me a little curious that we choose to use journals and RMW instead of a CoW solution to solve the write hole. 


Since we need on-disk changes to implement it, could it not be better to rethink the raid56 modes and implement a solution with full CoW, such as variable stripe extents etc? It is likely much more work, but could have better performance because it avoids double writes and RMW cycles too. 

Thanks 
 
Forza


  parent reply	other threads:[~2022-05-13 15:23 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-13  8:34 [PATCH 0/4] btrfs: cleanups and preparation for the incoming RAID56J features Qu Wenruo
2022-05-13  8:34 ` [PATCH 1/4] btrfs: remove @dev_extent_len argument from scrub_stripe() function Qu Wenruo
2022-05-13  8:47   ` Johannes Thumshirn
2022-05-13  8:34 ` [PATCH 2/4] btrfs: use btrfs_chunk_max_errors() to replace weird tolerance calculation Qu Wenruo
2022-05-13  8:45   ` Johannes Thumshirn
2022-05-13  8:34 ` [PATCH 3/4] btrfs: use btrfs_raid_array[] to calculate the number of parity stripes Qu Wenruo
2022-05-13  8:56   ` Johannes Thumshirn
2022-05-13  8:34 ` [PATCH 4/4] btrfs: use btrfs_raid_array[].ncopies in btrfs_num_copies() Qu Wenruo
2022-05-13  9:15   ` Johannes Thumshirn
2022-05-13  9:22     ` Qu Wenruo
2022-05-13  9:24       ` Johannes Thumshirn
2022-05-13  9:33         ` Qu Wenruo
2022-05-13 11:38 ` [PATCH 0/4] btrfs: cleanups and preparation for the incoming RAID56J features David Sterba
2022-05-13 12:21   ` Qu Wenruo
2022-05-13 15:14 ` Forza [this message]
2022-05-13 22:58   ` Qu Wenruo
2022-06-15 11:45 ` David Sterba

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