Re: POWER MODE and sat,12 again

Christian,	
	Date: Thu, 13 Aug 2015 22:02:21 +0200
	Subject: Re: [smartmontools-support] POWER MODE and sat,12 again
	
	> These are relatively up to date kernels, maintained in the RedHat
	> fashion (i.e changes are retrofitted to the base kernel release).
	> smart{d,ctl} have worked with sat,12 on this disk+enclosure without
	> problems in a sequence of kernels that ended with kernel 2.6.32-504.30.3.el6.
	> But now suddenly with the new kernel 2.6.32-573.1.1.el6 there are
	> problems (which eerely look like the problems we addressed in 2009).
	
	Then RH possibly broke something in the SAT layer.
	IIRC the SAT layer of more recent 2.6.* upstream kernels worked as
	expected and also supported -d sat[,16].
It very much looks to me then that RH added this broken situation
between 6.6 an 6.7 and between 6.6 and 7.0 or 7.1 (CentOS is RH with 
different branding). From my use of 6.6 (and before since 2009) I am 
sure that the problem wasn't there, and I have encountered it both on 
6.7 and 7.1. I guess I have to address the problem at CentOS and RH.
	
	> The strange thing is that only some SAT ATA PASS-THROUGH(12) commands
	> seem to fail, hdparm fails with "-S 180 --prefer-ata12" but works with
	> "-I --prefer-ata12" and smart{d,ctl} fail with "-n" but otherwise
	> work. In both failed cases POWER MODE is accessed. I haven't discovered
	> any other sat,12 accesses that caused problems. Is there something
	> special with accessing POWER MODE?
	
	Yes. The problem only occurs in the rare cases when the result is
	returned in ATA output registers:
	smartctl -H, -n standby, -l scterc
That matches of course exactly with my observation (and your explanation
of the -H WARNING).
	
	In SAT ATA PASS-THROUGH commands, the output registers are requested
	by CK_COND bit and returned in ATA RETURN DESCRIPTOR sense data. The
	SAT layer MUST NOT return a sense key indicating an error in this case
	(except when the ATA command has actually failed).
	
	> Any advice on how to proceed? Thanks, AG
	
	I probably will add some flag, e.g. "-d sat,12,i" to indicate that the
	error sense key should be ignored in this case.
That would be much appreciated.

Thanks for your help, AG

-- 
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   Alfred Ganz					alfred-ganz:at:agci.com
   AG Consulting				(203) 624-9667
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