linux-kernel - Re: [PATCH] scsi: sd: stop SSD (non-rotational) disks before reboot

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Message-ID: <20200618134904.GA26650@infradead.org>
Date:   Thu, 18 Jun 2020 06:49:04 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Simon Arlott <simon@...iron.net>
Cc:     Christoph Hellwig <hch@...radead.org>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Jonathan Corbet <corbet@....net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-scsi@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH] scsi: sd: stop SSD (non-rotational) disks before reboot

On Thu, Jun 18, 2020 at 01:25:18PM +0100, Simon Arlott wrote:
> On 18/06/2020 08:21, Christoph Hellwig wrote:
> > On Wed, Jun 17, 2020 at 07:49:57PM +0100, Simon Arlott wrote:
> >> Avoiding a stop of the disk on a reboot is appropriate for HDDs because
> >> they're likely to continue to be powered (and should not be told to spin
> >> down only to spin up again) but the default behaviour for SSDs should
> >> be changed to stop them before the reboot.
> > 
> > I don't think that is true in general.  At least for most current server
> > class and older desktop and laptop class systems they use the same
> > format factors and enclosures, although they are slightly divering now.
> > 
> > So I think this needs to be quirked based on the platform and/or
> > enclosure.
> 
> Are you referring to the behaviour for handling HDDs or SSDs?

All of the above.

> 
> For HDDs, the default "1" option could mean "automatic" and apply to
> rotational disks when power loss is expected.
> 
> For SSDs, I don't think an extra stop should ever be an issue.

Extra shutdowns will usually cause additional P/E cycles.