Slow performance on a DLT IV drive with tar and cpio on QNX

Nicolas_LAUGEON · June 8, 2001, 8:10pm

I am using a DLT IV tape drive connected to an Adaptec 3940 Wide SCSI card
and the speed of backup is as slow as my 4/8 Gb DAT drive.

The configuration of the SCSI card is set to the maximum speed (40Mb/sec),
Wide SCSI negotation ON.

tar is used with the -b20 option or cpio with the B option, and I am getting
less than 1Mb/sec throughput.
Backing up 3.5Gb of data took me 5 hours. It’s terrible.

Is there a way to increase the device’s buffer or something that streams
more data to the drive. One can tell by looking at it stopping every 3
seconds while writing data to the tape.

Nicolas LAUGEON
INFO ELECTRO
Papeete - Tahiti
French Polynesia.
qdn.public.qnx4

Slow performance on a DLT IV drive with tar and cpio on QNX 4

Tony_Mantler · June 11, 2001, 3:32pm

Previously, Nicolas LAUGEON wrote in qdn.public.qnx4:
[…]

Is there a way to increase the device’s buffer or something that streams
more data to the drive. One can tell by looking at it stopping every 3
seconds while writing data to the tape.
[…]

That sounds like the SCSI driver isn’t handling disconnects, a bigger buffer won’t help with that. (unless you want to buffer the whole tape into ram)

If this is indeed the case, you should be able to work around it by putting the tape drive on it’s own seperate scsi channel.

Cheers - Tony ‘Nicoya’ Mantler

John_Garvey1 · June 11, 2001, 4:00pm

Nicolas LAUGEON <nicinfo@mail.pf> wrote:
: tar is used with the -b20 option or cpio with the B option, and I am
: getting less than 1Mb/sec throughput.
: Backing up 3.5Gb of data took me 5 hours. It’s terrible.

You still have a lot of ‘-b’ to play with … have you tried upping to 63?

: Is there a way to increase the device’s buffer or something that streams
: more data to the drive. One can tell by looking at it stopping every 3
: seconds while writing data to the tape.