linux-kernel - Re: SATA hotplug from the user side ?

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Date:	Wed, 24 Jan 2007 11:07:25 +0900
From:	Tejun Heo <htejun@...il.com>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
CC:	Soeren Sonnenburg <kernel@....de>, Jeff Garzik <jeff@...zik.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: SATA hotplug from the user side ?

Henrique de Moraes Holschuh wrote:
> On Tue, 23 Jan 2007, Tejun Heo wrote:
>> Henrique de Moraes Holschuh wrote:
>>> Does SATA electrical conector keying let the disk firmware unload
>>> heads before the user manages to pull it out enough to sever power?
>> I don't think so.
> 
> Heh, thought as much. (Good) SCSI hotswap bays notice you pulled the disk
> release lever and issue an START_STOP_UNIT by themselves to the disk well
> before you have time to start pulling the disk out.  I wonder if the SATA
> ones do (I kind of doubt that, SATA seems to attract the el-cheapo, el-crapo
> crowd of manufacturers).

ahci controller spec has places for such thing but I've never seen it
actually implemented.  I'm thinking about a CLI tool to list & control
libata devices including hotplugging, NCQ and other stuff.  Eventually,
it would be really nice to give the user/admin easy gui/web/whatever
tool to watch and control ATA devices.

>>> If it does not, the drive will do an emergency head unload, which is
>>> not good and will likely reduce the drive's lifetime.
>> Probably.
> 
> So, that means it should be explained in the docs that you are to stop the
> disk first, if you can.

Yeap, agreed.

> Even if hald does this automatically, it would still be a very good idea to
> document the proper sequence, IMO...

Agreed.

-- 
tejun
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