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Re: LTO-3: optimizing blocksize
2007-08-01 12:28:09
On Wed, 1 Aug 2007 at 11:29am, Jean-Francois Malouin wrote
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.
Running amtapetype with different blocksize gives me ~386MB for
capacity (close enough to 400MB) but I never seem to get close to
streaming:
bs= speed=
32k 50482 kps
128k 50531 kps
256k 50508 kps
512k 50521 kps
1024k 50512 kps
2048k 15780 kps
4096k 15875 kps
Any hint on what I should try next?
Interesting. What if you try with dd or tar rather than amtapetype? On
my LTO3 drives testing with tar bs=32k yielded 41MiB/s while bs=2048k
yielded 60MiB/s.
Note also that LTO drives can throttle back to half of their native rate
(80MB/s for LTO3) without shoe-shining.
--
Joshua Baker-LePain
Department of Biomedical Engineering
Duke University
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