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From: pg@raid.list.sabi.co.UK (Peter Grandi)
To: list Linux RAID <linux-raid@vger.kernel.org>
Subject: Re: SSD based sw RAID: is ERC/TLER really important?
Date: Mon, 26 Jul 2021 18:12:05 +0200	[thread overview]
Message-ID: <24830.57045.462708.449341@cyme.ty.sabi.co.uk> (raw)
In-Reply-To: <24830.27358.78544.178603@cyme.ty.sabi.co.uk>

[...]
> I have also noticed that XFS bizarrely has its own layer of
> recovery on top of that of the Linux IO subsystems and of the
> device itself:

>   https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/managing_file_systems/configuring-xfs-error-behavior_managing-file-systems
>   https://elixir.bootlin.com/linux/v5.13.5/source/fs/xfs/xfs_buf.c#L1264

Some people have been proposing to do the same with MD RAID, and
some similar layer sometimes is embedded in the firmware of
hardware RAID host adapters.

Consider this scenario (include the relevant error handling and
timeouts):

  * The device firmware does physical operation retries.
  * The Linux IO subsystem does device operation retries.
  * MD RAID does Linux IO operation retries.
  * XFS does MD RAID IO operation retries.

Is there something weird with this?

BTW there is something similar with read ahead or write behind:
sometimes several software layers assume that lower software
layers are doing too little of it, and do their own additional
read ahead or write behind.

  reply	other threads:[~2021-07-26 16:12 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-24 18:41 SSD based sw RAID: is ERC/TLER really important? Gianluca Frustagli
2021-07-24 20:19 ` Peter Grandi
2021-07-24 21:45   ` Phil Turmel
2021-07-25  7:00     ` Wols Lists
2021-07-25 10:28     ` Peter Grandi
2021-07-26  1:06       ` Phil Turmel
2021-07-26  7:57         ` Peter Grandi
2021-07-26 16:12           ` Peter Grandi [this message]
2021-07-25 11:04     ` Peter Grandi
2021-07-24 20:21 ` Andy Smith

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