* Jean-Francois Malouin <[EMAIL PROTECTED]> [20070801 14:05]: > * Joshua Baker-LePain <[EMAIL PROTECTED]> [20070801 12:20]: > > On Wed, 1 Aug 2007 at 11:29am, Jean-Francois Malouin wrote > > Hi Joshua, > > > > > >Hardware: > > >I've setup the default access device to the drives as non-compressing. > > >The library is hooked through a LSI U320 PCI-X scsi card to a 4 > > >DualCore2 Xeon with 8GB of RAM running Debian/Etch running a 64bit > > >kernel 2.6.21.5-i686-64-smp. It should be beefy enough :) > > > > If you ever want to use both drives simultaneously, you'll need a dual > > channel SCSI card and each drive will need to be on its own channel. > > Trust me on this one -- I tried every trick I could think of with 2 drives > > on one channel (there should be plenty of bandwidth, right!?), but > > couldn't get decent speeds when using both drives. > > I tried running amtapetype simultaneously and on each tape on it's own > and I didn't see any differences in the transfer rates but since they > seem to throttle back to half-speed maybe I wasn't hitting their > bottlenecks.
My bad, replying to myself... Here's the outpout of 2 simultaneous running dd's on non-compressing tape devices daisy-chained to the same scsi hba (LSI U320 PCI-X): grumpy:~# time dd if=/dev/zero of=/dev/nst0 bs=32k dd: writing `/dev/nst0': No space left on device 12424636+0 records in 12424635+0 records out 407130439680 bytes (407 GB) copied, 7003.39 seconds, 58.1 MB/s real 116m43.419s user 0m11.317s sys 3m7.260s grumpy:~# time dd if=/dev/zero of=/dev/nst1 bs=32k dd: writing `/dev/nst1': No space left on device 12424636+0 records in 12424635+0 records out 407130439680 bytes (407 GB) copied, 7002.45 seconds, 58.1 MB/s real 116m42.477s user 0m11.677s sys 3m6.480s Looks good to me. Not sure why amtapetype tops at 40MBs. jf -- <° ><