[Beowulf] Re: OT: LTO Ultrium (3) throughput? (Steve Cousins)

[David Mathog]

Steve Cousins <cousins at umit.maine.edu> wrote:

> > Just under 60MB/sec seems to be the maximum tape transport read/write
> > limit.  Pretty reliably the first write from the beginning of tape was a
> > bit slower than writes started further into the tape.
> 
> I believe LTO-3 is rated at 80 MB/sec without compression.

I just checked that.  The spec page here:

http://h18006.www1.hp.com/products/storageworks/ultrium920/index.html

says:

Higher performance with dynamic data rate matching - Ultrium 920 Tape
Drive 120MB/sec compressed data transfer using 2:1 compression,

Or with compression off 60MB/sec, assuming that the 120MB/s was rate
limited by the physical tape write speed and not at all by the
compression.  On the other hand, the specs for the CARTRIDGE here:

http://www.hboutlet.com.au/catalog/product_info.php?products_id=181385

list 80MB/s uncompressed, which is the number you cited.  Also here:
  http://en.wikipedia.org/wiki/Linear_Tape-Open
they cite 80MB/s.

Do different LTO-3 drives have different maximum tape write speeds?

Regards,

David Mathog
mathog at caltech.edu
Manager, Sequence Analysis Facility, Biology Division, Caltech