Re: [Patch] SCSI: Retrieve Cache Mode Using SG_ATA_16 if normal routine fails

[Hannes Reinecke <hare-l3A5Bk7waGM@public.gmane.org>]

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
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Dr. Hannes Reinecke		      zSeries & Storage
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