Re: DLT-V4

Island Computers, D B Turner wrote:
It works

It's just slower than the regular SDLT

The DLT-S4, on the other hand, is twice as fast as our previous
drive, an SDLT320, and has 800 Gb capacity (uncompressed data).
I can't say how it would perform on a VMS system, but a Solaris
ufsdump of a large "stripe set" (in VMS terms) of 4 internal fibre channel disks to the old SDLT320 had a sustained write rate of just under 22Mb/s, whereas the replacement DLT-S4 sustains writes
at just under 42 Mb/sec. The specs say that this drive can sustain 60 Mb/sec without compression, 120 Mb/sec compressed, and 320 Mb/sec burst (not compressed). The V880 ours is on apparently can't dump that fast sustained. Using dd to write directly to the drive with:

time dd if=/dev/zero of=/dev/rmt/0cn bs=64512 count=500000

took 298 seconds real time, for a sustained data rate of
64512*500000/298 = 108Mb/sec. Slightly slower than the published
maximum compressed rate. To the 0ln (no compression device)
it took 510 seconds real time, for a sustained rate of 63.4 Mb/sec
(=60 MB/sec, where MB is 2^20 and not 10^6) which matches the
specs.

The tape drive is clearly limiting in the dd tests since changing
the output file to /dev/null resulted in a run time of only 20 seconds,
or around 1.6 Gb/sec.


FYI We have some real SDLT 320 Tabletops for $1995 refurbished with 1 yr
warranty

The V4 is around $1000 new (depending on enclosure) and the S4 is $5000
for a new bare drive. Not surprisingly, one must pay for performance.

Regards,

David Mathog
.