Re: Losing paths

[Hannes Reinecke <hare@suse.de>]

Hi John,

Romanowski, John (OFT) wrote:
> Hi,
> We had similar problem last year using sles9 and SVC 4.2.0.2,  as you describe: adding/deleting a LUN causes
> brief path failures for the host's remaining, unaffected LUNs.
> 
> We were using tur checker and it turned out that while adding/deleting a LUN (and some other admin tasks)
> the SVC does not respond well to test-unit-ready tur requests; but it responds perfectly well to normal read
> commands. I opened IBM PMR 43118 on that if you want to ask the SVC folks about it.  
> 
> Workaround for us was to use readsector0 instead of  tur as multipath path checker. 
>  
> Recent post here (see July 8, 2008)  said multipath-tools is deprecating readsector0, and to use directio as
> path checker, but directio was said to be much slower than tur, implying tur was better replacement than
> directio for readsector0. 
>
Only for those cases where no actual read-access is necessary.
 
> Not sure what deprecating readsector0 means for us SVC users.  
> 
It means you should be using directio there.

Thanks for the information, I'll see to have it included in SLES10.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
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