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Re: amanda performance
2005-12-16 12:31:16
On Fri, 16 Dec 2005 at 12:08pm, Gene Heskett wrote
On Friday 16 December 2005 11:42, Joshua Baker-LePain wrote:
A single drive is going to have an awfully hard time... scratch that.
A single drive can *not* feed an lto3 drive as fast as it wants to
be fed (even if that's the only thing it's trying to do). I've got
a 4 disk hardware RAID0 feeding my lto3 drive.
Ahh, I'd argue that point Roy. Of the two active drives on this
machine, the main one is a 120GB, and I'm using a 200G as virtual
disk. These are on seperate cables of the same on board nforce2
controller. As all drives here have dma enabled, the hdparm -tT test
returns are typically in the 50-60 mb/second rate. I did have a scsi
controller in here at one time but the tape died so it was removed.
But while it was installed, I was able to get 20mg/second transfers to
another smallish scsi drive hooked up temporarily. The drive was
rated as scsi-2-fast, as was the advansys controller.
Overland's datasheet for my Neo2K says the native transfer rate w/ 1 LTO3
drive is 288GB/hour, which translates to 80MB/s. LTO3 drives are *fast*.
AIUI, they'll throttle down to 1/2 that without starting DLT-like
shoe-shining behavior, but even 40MB/s is pretty quick.
If this user is only getting 2.5mb/sec, something is wrong with the
config someplace. I'd start with the hdparm -Tt /dev/whatever tests
and see if the dma can be enabled all across the board.
Oh, absolutely. He should definitely be getting better speeds than he is.
I was simply pointing out that a single disk holding area ain't gonna' cut
it in production for lto3.
--
Joshua Baker-LePain
Department of Biomedical Engineering
Duke University
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