On Fri, May 7, 2010 at 8:07 AM, Emily Grettel <emilygrettelis...@hotmail.com > wrote:
> Hi, > > I've had my RAIDz volume working well on SNV_131 but it has come to my > attention that there has been some read issues with the drives. Previously I > thought this was a CIFS problem but I'm noticing that when transfering files > or uncompressing some fairly large 7z (1-2Gb) files (or even smaller rar - > 200-300Mb) files occasionally running iostat will give the b% as 100 for a > drive or two. > That's the percent of time the disk is busy (transactions in progress) - iostat(1M). > > I have the Western Digital EADS 1TB drives (Green ones) and not the more > expensive black or enterprise drives (our sysadmins fault). > > The pool in question spans 4x 1TB drives. > > What exactly does this mean? Is it a controller problem disk problem or > cable problem? I've got this on commodity hardware as its only used for a > small business with 4-5 staff accessing our media server. Its using the > Intel ICHR SATA controller. I've already changed the cables, swapped out the > odd drive that exhibted this issue and the only thing I can think of is to > buy a Intel or LSI SATA card. > > The scrub sessions take almost a day and a half now (previously at most > 12hours!) but theres also 70% of space being used (files wise they're chunky > MPG files) or compressed artwork but there are no errors reported. > > Does anyone have any ideas? > You might be maxing out your drives' I/O capacity. That could happen when ZFS is commting the transactions to disk every 30 seconds but if %b is constantly high you disks might not be keeping up with the performance requirements. We've had some servers showing high asvc_t times but it turned out to be a firmware issue in the disk controller. It was very erratic (1-2 drives out of 24 would show that). If you look in the archives, people have sent a few averaged I/O performance numbers that you could compare to your workload. -- Giovanni
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