From: Jeff Garzik <jeff@garzik.org>
To: Matthew Wilcox <matthew@wil.cx>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Jens Axboe <jens.axboe@oracle.com>,
rwheeler@redhat.com, snitzer@redhat.com, neilb@suse.de,
dgilbert@interlog.com, linux-ide@vger.kernel.org,
linux-scsi@vger.kernel.org
Subject: Re: [PATCH 5 of 8] sd: Detect non-rotational devices
Date: Thu, 23 Apr 2009 10:39:41 -0400 [thread overview]
Message-ID: <49F07DAD.7080107@garzik.org> (raw)
In-Reply-To: <20090423141644.GP1926@parisc-linux.org>
Matthew Wilcox wrote:
> On Thu, Apr 23, 2009 at 02:10:13PM +0000, James Bottomley wrote:
>> I'm with Jeff on this one. We had an identically similar problem with
>> REPORT LUNS, which, today is the basis of SCSI discovery.
>
> Yes, REPORT LUNS is quite essential.
>
> It's not exactly in the same category as reporting device form factor
> and rotational speed. If REPORT LUNS is wrong, we're in really deep
> trouble. If device form factr is wrong ... umm ... nothing much happens.
> If rotational speed is wrong, we might have a suboptimal IO pattern.
If the general attitude is "oh, that info might be wrong", why will app
developers bother at all?
It is better to return zeroes than have a decent probability of
returning garbage. I value predictability much more than adopting a
generalized rule to handle a few special case early adopters.
> It's also fixable by udev.
By that logic we should leave it to udev to handle the ata_version <= 7
stuff, since that is the early adopter special case.
Jeff
next prev parent reply other threads:[~2009-04-23 14:39 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-23 5:29 [PATCH 0 of 8] I/O topology patch kit Martin K. Petersen
2009-04-23 5:29 ` [PATCH 1 of 8] block: Expose stacked device queues in sysfs Martin K. Petersen
2009-04-23 5:29 ` [PATCH 2 of 8] block: Export I/O topology for block devices and partitions Martin K. Petersen
2009-04-23 10:51 ` Jens Axboe
2009-04-23 11:49 ` Matthew Wilcox
2009-04-23 11:55 ` Jens Axboe
2009-04-23 13:22 ` Matthew Wilcox
2009-04-23 13:30 ` Matthew Wilcox
2009-04-23 13:17 ` Martin K. Petersen
2009-04-23 18:13 ` Konrad Rzeszutek
2009-04-23 18:26 ` Ric Wheeler
2009-04-23 18:44 ` Matthew Wilcox
2009-04-23 18:34 ` Martin K. Petersen
2009-04-23 5:29 ` [PATCH 3 of 8] MD: Use new topology calls to indicate alignment and I/O sizes Martin K. Petersen
2009-04-23 5:29 ` [PATCH 4 of 8] sd: Physical block size and alignment support Martin K. Petersen
2009-04-23 16:37 ` Konrad Rzeszutek
2009-04-23 18:25 ` Martin K. Petersen
2009-04-23 18:44 ` Konrad Rzeszutek
2009-04-23 19:02 ` Martin K. Petersen
2009-04-23 5:29 ` [PATCH 5 of 8] sd: Detect non-rotational devices Martin K. Petersen
2009-04-23 10:52 ` Jens Axboe
2009-04-23 11:09 ` Jeff Garzik
2009-04-23 11:13 ` Jens Axboe
2009-04-23 11:22 ` Jeff Garzik
2009-04-23 11:38 ` Matthew Wilcox
2009-04-23 11:58 ` Jeff Garzik
2009-04-23 12:03 ` Jens Axboe
2009-04-23 13:16 ` Martin K. Petersen
2009-04-23 13:33 ` Jeff Garzik
2009-04-23 14:10 ` James Bottomley
2009-04-23 14:16 ` Matthew Wilcox
2009-04-23 14:39 ` Jeff Garzik [this message]
2009-04-23 17:25 ` Matthew Wilcox
2009-04-23 17:37 ` James Bottomley
2009-04-23 5:29 ` [PATCH 6 of 8] sd: Block limits VPD support Martin K. Petersen
2009-04-23 5:29 ` [PATCH 7 of 8] scsi_debug: Add support for physical block exponent and alignment Martin K. Petersen
2009-04-23 5:29 ` [PATCH 8 of 8] libata: Report disk alignment and physical block size Martin K. Petersen
2009-04-23 13:46 ` Matthew Wilcox
2009-04-23 14:05 ` Martin K. Petersen
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