gary artim wrote:
Hi Rodger --
Thanks for the quick responses. The backup unit is a Overland arcvault
12 w/lto4 drive. The lto4 have,
I think, 120MBps (Native)/240MBps (compressed), so no gain using U320
interface? I'd guess the max thru put
would be 120MBs, with the compressed rate just accomplished because of
data compressing. Sorry to
be thinking out loud here, but this does help!
-- G
Well, if that is what you have, you did spend some decent money on it.
The important part it LTO4. Native speed is 432GB/hr, or 120MB/second, if you
get good compression and you have a *FAST* disk subsystem, then you could use
that speed, I would test doing a backup with you backup software to /dev/null
and see what the actual disk speed is, if you are backing up a lot of small
files you won't be able to use all of the speed, or if the files are fragmented
on disk you may not be able to use that speed.
If you data does not compress good you won't be able to go over 160 MB/second
either.
You would have to be getting the data locally from a high-end disk subsystem,
and you have to have big files, and you would have to data that was
compressible. Overall you have to be pretty careful to get something that
will read at 120MB/second and also write out to a tape at 120MB/second, you have
to make sure the PCI-X slots are not shared with each other, and that all other
subsystems can do it.
And if your current SCSI card is PCI (not-X, not-64bit) then the actual limit
is probably < 132MB/sec (PCI limit).
I would try what you have and see what speed you are getting, if you run within
20-30 of the limit you may be hitting the limit, if you are much below that you
have other issues.
Generally though I have had good luck with the LSI cards, I have used their
SCSI, SAS, and fiber channel cards of various sorts. If I was getting one of
those new I would have got either a SAS or a Fiber channel interface for it (if
it was available), as they tend to be less trouble than SCSI.
Roger
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