On 08/26/2012 01:10 AM, Timothy Coalson wrote: > On Sat, Aug 25, 2012 at 1:56 PM, Sašo Kiselkov <skiselkov...@gmail.com> wrote: >> On 08/25/2012 03:42 PM, Jordan McQuown wrote: >>> I can say from experience chaining supermicro sas chassis with any type of >>> disk can be a recipe for disaster. Lsiutil reported a couple million errors >>> in a couple months time which eventually led to some sort of contention and >>> corruption on both sides of our mirrors. These were also SAS and not sata >>> disks. >> >> Have you checked your SAS cabling? Also, lsiutil is for lsi1068 (3G) SAS >> chips. I've got a SuperMicro SC847 attached to a pair of lsi >> sas2008-based boards. The chassis is internally arranged as a pair of >> backplanes, each with two LSI SAS2x36, chained to appear as a single >> connector from the back of the chassis (i.e. one connector per SAS >> channel bundle for two fully redundant paths to the drives). Initially I >> was having trouble with excessive link errors which resulted in poor >> performance, lots of errors and generally lots of problems, but I found >> this was caused by a faulty SAS cable between the host and the chassis. >> Ever since playing around with cabling a bit it's been ticking reliably >> like a Swiss clock. >> > > Good to know it is working for you, that is precisely the kind of > setup I was considering. Did I understand you correctly that even > with redundant paths to each drive, a single poor connection, despite > a secondary good connection, caused serious performance problems? > > Thanks for the replies.
Correct. The problem was that the scsi_vhci driver was trying a round-robin approach to load-balancing, so half the commands were hitting the good path and half the bad one (which lagged and lead to losses). There is no redundancy mechanism that is impervious to non-gracious hardware failures, and storage systems are commonly affected by this (despite what any manufacturer tells you). -- Saso _______________________________________________ OpenIndiana-discuss mailing list OpenIndiana-discuss@openindiana.org http://openindiana.org/mailman/listinfo/openindiana-discuss
