From: Hannes Reinecke <hare@suse.de>
To: Amit Sahrawat <amit.sahrawat83@gmail.com>
Cc: James Bottomley <James.Bottomley@hansenpartnership.com>,
Alan Stern <stern@rowland.harvard.edu>,
Douglas Gilbert <dgilbert@interlog.com>,
linux-usb@vger.kernel.org, linux-scsi@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Christoph Hellwig <hch@infradead.org>,
NamJae Jeon <linkinjeon@gmail.com>
Subject: Re: [Patch] SCSI: Retrieve Cache Mode Using SG_ATA_16 if normal routine fails
Date: Tue, 11 Oct 2011 12:41:34 +0200 [thread overview]
Message-ID: <4E941D5E.6060101@suse.de> (raw)
In-Reply-To: <CADDb1s2=Ykh711grVjHV542pVJwpf1K+zzTRVEY2KH3T=wB_xg@mail.gmail.com>
On 10/11/2011 10:26 AM, Amit Sahrawat wrote:
> SCSI: Retrieve Cache Mode Using SG_ATA_16 if normal routine fails
>
> It has been observed that a number of USB HDD's do not respond correctly
> to SCSI mode sense command(retrieve caching pages) which results in their
> Write Cache being discarded by queue requests i.e., WCE if left set to
> '0'(disabled). So, in order to identify the devices correctly - give it
> a last try using SG_ATA_16 after failure from normal routine.
>
I'd be _VERY_ cautious when trying something like this.
ATA_16 is a rather recent command, and most older drives simply
can't cope with this. Instead they just kick the error handler and
go offline eventually.
Shouldn't we rather use a sensible default, ie assume WCE is enabled?
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@suse.de +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
next prev parent reply other threads:[~2011-10-11 10:41 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-11 8:26 Amit Sahrawat
2011-10-11 10:41 ` Hannes Reinecke [this message]
2011-10-11 10:55 ` Amit Sahrawat
2011-10-11 11:59 ` NamJae Jeon
2011-10-11 13:42 ` Jeff Garzik
2011-10-11 14:05 ` James Bottomley
2011-10-11 16:00 ` Amit Sahrawat
2011-10-11 14:19 ` Alan Stern
2011-10-11 16:03 ` Amit Sahrawat
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