An excellent example of higher speed and capacity tape drive.  However,
your assertion is incorrect.  Looking at the small ADIC library you
mentioned, one can see it has a maximum of 6 drives.  HP resells a
StorageTek library called the 20/700, which has, you guessed it, 20 LTO
drives.  The library throughput is phenomenal, as is the overall capacity
and the price.  However, you are trying to say given 2 TB/hour of
throughput or more, one should be able to backup a 400GB drive in mere
minutes.

Well, I am here to tell you it won't happen that way.  Even if your backup
product could drive all the tape drives in the library simultaneously,
which many can, the disk drive does not have the sustained throughput that
can stream even one LTO drive, let alone 6 or 20.  These tape drives can
accept and write in excess of 15 MB/second, which translates to 54GB/hour,
native.  With compression the speed can double.  Currently, there is not a
single disk drive that can put out that much data, in a sustained fashion.
 Yes, they have a burst speed of 80MB/second, but they won't keep that
speed up for many seconds, or even fractions of a second.  If you do a
filesystem backup, the heads will be dancing all over the drive cutting
down the throughput to a mere fraction of the tape drive.

The backup issue is not really how fast the tape devices are, but rather
how fast you can get the data of the disks and on its way to the tape
drive.

Conversely, the restore issue is how fast you can write the data on the
disks in a coherent, useful manner, not how fast you can read off the tape
drive.

Kind regards,

Denys. . .

Denys Beauchemin
HICOMP
(800) 323-8863  (281) 288-7438         Fax: (281) 355-6879
denys at hicomp.com                             www.hicomp.com

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