Date: Tue, 27 Jun 2006 08:25:50 -0500 From: Eric Anderson <anderson@centtech.com> To: Jerlique Bahn <jerlique@webscene.com.au> Cc: freebsd-scsi@freebsd.org Subject: Re: Viewing SCSI errors.. Message-ID: <44A131DE.3010702@centtech.com> In-Reply-To: <005901c699ec$7d70bdb0$6400000a@WKSTN501> References: <005901c699ec$7d70bdb0$6400000a@WKSTN501>
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Jerlique Bahn wrote: >>> I've added a tape drive to my server and the drive only seems to work at >>> 2MBps. The drive should be doing about 24MBps. The tape is a DELL 110T >> LTO2 >>> which runs at about 86Gb/hr. >>> >>> I am trying to diagnose where my problems could lie, and was wondering >> how I >>> could see if there are any errors in the communication between the tape >> and >>> the scsi card (320Mbps). I'm quite confident the speed issue is related >> to >>> the tape drive or the scsi chain. >>> >>> Your suggestions welcomed. >> >> How did you measure the 2MBps number? > > With iostat, eg > > # iostat 5 > tty amrd0 amrd1 sa0 cpu > tin tout KB/t tps MB/s KB/t tps MB/s KB/t tps MB/s us ni sy in id > 0 12 57.81 2 0.13 53.21 6 0.32 31.99 24 0.76 0 0 1 0 99 > 0 46 8.00 0 0.00 0.00 0 0.00 32.00 88 2.74 0 0 0 0 100 > 0 16 0.00 0 0.00 16.00 0 0.01 32.00 87 2.73 0 0 1 0 99 > 0 15 0.00 0 0.00 0.00 0 0.00 32.00 88 2.74 0 0 0 0 100 > 0 16 0.00 0 0.00 0.00 0 0.00 32.00 88 2.74 0 0 0 0 99 > > JB What tool was writing to the tape? Most of the time, tapes require you to stream the data evenly to it, to avoid 'shoe shining'. I usually use something like: tar -b 256 ... or use a buffering tool to buffer the data going to the tape device (use a pipe). You might try some various bs= arguments to dd, to see if you can get the throughput up. Eric -- ------------------------------------------------------------------------ Eric Anderson Sr. Systems Administrator Centaur Technology Anything that works is better than anything that doesn't. ------------------------------------------------------------------------
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