We've been using 65537k for transfer buffers for at least half a year at
the recommendation of some docs, and 16384k before that. We also used
64k block size on the LTO2 tapes because it gained us a few megabytes
per second (128k did not work), but I hope to avoid going over approx
63k because some operating systems need tuning or kernel hacking to do
larger transfers than 64k. We have not attempted a direct SCSI
connection with LTO4 yet (maybe next week, not on a Friday afternoon
before the weekend backups start).
Davies,Matt wrote:
> Couple of thoughts, increasing the number of buffers, within the
> performance tab of configure for the tape drive and changing the block
> size.
>
> Cheers
>
> Matt
>
>
> -----Original Message-----
> From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com]
> On Behalf Of Adam McDougall
> Sent: 09 May 2008 16:02
> To: Toasters
> Subject: Max of 20MB/sec through FC attached LTO tape drive? Overland
> neo 2000
>
> Asking here because we don't have current Overland support for the fibre
>
> channel card and I would guess it is more of a problem with the card
> rather than netapp (we only used the FCO with a netapp), but maybe
> someone has encountered this...
>
> Around 2004 we bought a Overland Neo 2000 tape library with the FCO VIA
> scsi to FC converter board, and we got at most 20 or 25MB/sec through it
>
> (per tape drive) depending if we were writing or reading. This is both
> with NDMP dumps from the filer disks to tape, and also across the
> network into the filer to tape with NDMP. The backup software is
> Bakbone Netvault. Last year we tried attaching this library to a Unix
> host directly with SCSI and our speed almost doubled. I was floored,
> and shocked that we spent so many years missing out on performance,
> although 20-25 was the best I've seen anyone report for LTO2 so I never
> expected more.
>
> Recently we bought another Neo 2000 with LTO4 drives, and I decided to
> move the FCO card over to it and try again, hoping maybe there was a
> misconfiguration, but I could not find any and it still acts as if there
>
> is a mystery cap on the speed of 20MB/sec (it averages 18-19 after it
> gets going). I've been all through the configuration of the FCO card
> and it is set to 160M/sec per scsi bus, tried with and without domain
> validation, and I even got the FC channel to operate at 2Gbit but no
> improvement. If I cannot figure this out then I will just attach it to
> the Unix host with the other neo 2000, but its always nice to have more
> options. I would not bother operating a LTO4 drive at such a slow speed
>
> in production because shoe-shining would probably wear it out and the
> compression would be sub optimal or non-existent.
>
>
>
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