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From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Damien Le Moal <damien.lemoal@wdc.com>
Cc: linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
	linux-scsi@vger.kernel.org,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	linux-ide@vger.kernel.org, Hannes Reinecke <hare@suse.de>
Subject: Re: [PATCH v3 0/4] Initial support for multi-actuator HDDs
Date: Thu, 05 Aug 2021 23:41:55 -0400	[thread overview]
Message-ID: <yq18s1ffdz7.fsf@ca-mkp.ca.oracle.com> (raw)
In-Reply-To: <20210726013806.84815-1-damien.lemoal@wdc.com> (Damien Le Moal's message of "Mon, 26 Jul 2021 10:38:02 +0900")


Damien,

> Single LUN multi-actuator hard-disks are cappable to seek and execute
> multiple commands in parallel. This capability is exposed to the host
> using the Concurrent Positioning Ranges VPD page (SCSI) and Log (ATA).
> Each positioning range describes the contiguous set of LBAs that an
> actuator serves.

I have to say that I prefer the multi-LUN model.

> The first patch adds the block layer plumbing to expose concurrent
> sector ranges of the device through sysfs as a sub-directory of the
> device sysfs queue directory.

So how do you envision this range reporting should work when putting
DM/MD on top of a multi-actuator disk?

And even without multi-actuator drives, how would you express concurrent
ranges on a DM/MD device sitting on top of a several single-actuator
devices?

While I appreciate that it is easy to just export what the hardware
reports in sysfs, I also think we should consider how filesystems would
use that information. And how things would work outside of the simple
fs-on-top-of-multi-actuator-drive case.

-- 
Martin K. Petersen	Oracle Linux Engineering

  parent reply	other threads:[~2021-08-06  3:42 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-26  1:38 [PATCH v3 0/4] Initial support for multi-actuator HDDs Damien Le Moal
2021-07-26  1:38 ` [PATCH v3 1/4] block: Add concurrent positioning ranges support Damien Le Moal
2021-07-26  7:33   ` Hannes Reinecke
2021-07-26  8:30     ` Damien Le Moal
2021-07-26  8:47       ` Hannes Reinecke
2021-07-26 11:33         ` Damien Le Moal
2021-07-27 14:07           ` Paolo Valente
2021-07-27 23:44             ` Damien Le Moal
2021-08-10  8:23   ` Christoph Hellwig
2021-08-10 11:03     ` Damien Le Moal
2021-08-10 16:02       ` hch
2021-08-10 23:46         ` Damien Le Moal
2021-07-26  1:38 ` [PATCH v3 2/4] scsi: sd: add " Damien Le Moal
2021-08-10  8:24   ` Christoph Hellwig
2021-07-26  1:38 ` [PATCH v3 3/4] libata: support concurrent positioning ranges log Damien Le Moal
2021-07-26  7:34   ` Hannes Reinecke
2021-08-10  8:26   ` Christoph Hellwig
2021-07-26  1:38 ` [PATCH v3 4/4] doc: document sysfs queue/cranges attributes Damien Le Moal
2021-07-26  7:35   ` Hannes Reinecke
2021-08-10  8:27   ` Christoph Hellwig
2021-08-10 11:04     ` Damien Le Moal
2021-07-28 22:59 ` [PATCH v3 0/4] Initial support for multi-actuator HDDs Damien Le Moal
2021-08-06  2:12 ` Damien Le Moal
2021-08-06  3:41 ` Martin K. Petersen [this message]
2021-08-06  4:05   ` Damien Le Moal
2021-08-06  8:35     ` Hannes Reinecke
2021-08-06  8:52       ` Damien Le Moal

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