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Re: [dm-devel] Losing paths



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
hare suse de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
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