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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