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From: Shaohua Li <shli@kernel.org>
To: linux-raid@vger.kernel.org
Cc: jes.sorensen@gmail.com, neilb@suse.de
Subject: RAID creation resync behaviors
Date: Wed, 3 May 2017 13:27:48 -0700	[thread overview]
Message-ID: <20170503202748.7r243wj5h4polt6y@kernel.org> (raw)

Hi,

Currently we have different resync behaviors in array creation.

- raid1: copy data from disk 0 to disk 1 (overwrite)
- raid10: read both disks, compare and write if there is difference (compare-write)
- raid4/5: read first n-1 disks, calculate parity and then write parity to the last disk (overwrite)
- raid6: read all disks, calculate parity and compare, and write if there is difference (compare-write)

Write whole disk is very unfriendly for SSD, because it reduces lifetime. And
if user already does a trim before creation, the unncessary write could make
SSD slower in the future. Could we prefer compare-write to overwrite if mdadm
detects the disks are SSD? Surely sometimes compare-write is slower than
overwrite, so maybe add new option in mdadm. An option to let mdadm trim SSD
before creation sounds reasonable too.

Thanks,
Shaohua

             reply	other threads:[~2017-05-03 20:27 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-03 20:27 Shaohua Li [this message]
2017-05-03 21:06 ` RAID creation resync behaviors David Brown
2017-05-04  1:54   ` Shaohua Li
2017-05-04  7:37     ` David Brown
2017-05-04 16:02       ` Wols Lists
2017-05-04 21:57       ` NeilBrown
2017-05-05  6:46         ` David Brown
2017-05-04 15:50     ` Wols Lists
2017-05-04 22:00       ` NeilBrown
2017-05-03 23:58 ` Andreas Klauer
2017-05-04  2:22   ` Shaohua Li
2017-05-04  7:55     ` Andreas Klauer
2017-05-04  8:06       ` Roman Mamedov
2017-05-04 15:20       ` Brad Campbell
2017-05-04  1:07 ` NeilBrown
2017-05-04  2:04   ` Shaohua Li
2017-05-09 18:39     ` Jes Sorensen
2017-05-09 20:30       ` NeilBrown
2017-05-09 20:49         ` Jes Sorensen
2017-05-09 21:03           ` Martin K. Petersen
2017-05-09 21:11             ` Jes Sorensen
2017-05-09 21:16               ` Martin K. Petersen
2017-05-09 21:22                 ` Jes Sorensen
2017-05-09 23:56                   ` Martin K. Petersen
2017-05-10  5:58                   ` Hannes Reinecke
2017-05-10 22:20                     ` Martin K. Petersen
2017-05-10 17:30                   ` Shaohua Li

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