From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Chris Murphy <lists@colorremedies.com>
Cc: Linux RAID Mailing List <linux-raid@vger.kernel.org>
Subject: Re: Why 4k native drives haven't arrived
Date: Sun, 12 Jan 2014 08:55:54 -0500 [thread overview]
Message-ID: <yq1txd9nw2d.fsf@sermon.lab.mkp.net> (raw)
In-Reply-To: <6AACF77C-5D54-4ABF-AA2D-FC3F4F1E141C@colorremedies.com> (Chris Murphy's message of "Sat, 11 Jan 2014 21:01:02 -0700")
>>>>> "Chris" == Chris Murphy <lists@colorremedies.com> writes:
Chris> Huh. Two more cases. All three involve USB enclosures. Bug or
Chris> feature?
Feature.
Chris> Is it possible the enclosure's bridge chipset is disabling the
Chris> drive's 512-byte emulation?
There's nothing to disable. If the USB-SATA bridge exposes 4K logical
blocks to the host all accesses will inevitably be aligned multiples of
4K. All the bridge needs to do is adjust LBA and transfer length. Not
unlike how we handle 1/2/4Kn in the Linux SCSI disk driver given that
the block layer always uses 512-byte sectors.
The two 4Kn USB drives I have both use 512e drives internally:
# sg_readcap -l /dev/sdd | grep Logical
Logical block length=4096 bytes
Logical blocks per physical block exponent=0
# hdparm -I /dev/sdd | grep Sector
Logical Sector size: 512 bytes
Physical Sector size: 4096 bytes
Logical Sector-0 offset: 0 bytes
It is conceivable that there are other USB drives out there that
actually use 4Kn drives inside but I doubt it. All the 4Kn SATA drives I
have in the lab are engineering samples...
--
Martin K. Petersen Oracle Linux Engineering
next prev parent reply other threads:[~2014-01-12 13:55 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-09 21:49 Why 4k native drives haven't arrived Chris Murphy
2014-01-12 4:01 ` Chris Murphy
2014-01-12 13:55 ` Martin K. Petersen [this message]
[not found] ` <F92ECEC1-D375-498B-8C6A-C88C815C325F@colorremedies.com>
2014-01-12 18:32 ` Martin K. Petersen
2014-01-12 19:04 ` Chris Murphy
2014-01-12 19:27 ` Chris Murphy
2014-01-12 20:25 ` Roman Mamedov
2014-01-12 18:41 ` Stan Hoeppner
-- strict thread matches above, loose matches on Subject: below --
2014-01-03 1:53 Stan Hoeppner
2014-01-03 11:23 ` Mikael Abrahamsson
2014-01-03 11:27 ` Dimitri John Ledkov
2014-01-23 2:19 ` Phillip Susi
2014-01-03 21:04 ` Martin K. Petersen
2014-01-04 18:40 ` Stan Hoeppner
2014-01-06 23:35 ` Martin K. Petersen
2014-01-05 18:48 ` Peter Grandi
2014-01-06 23:50 ` Martin K. Petersen
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