Re: SCSI tape backup for 9406-170 -- MIDRANGE-L

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On Wed, Nov 15, 2023 at 5:31 PM Patrik Schindler <poc@xxxxxxxxxx> wrote:

One thing to consider is the data transfer rate. Because of the very
nature of OS/400, data being saved is read from DASD through (demand)
paging — being at the very core of the OS foundation. This is highly
optimized for low latency (to quickly bring a record from disk to the
screen) but isn't exactly a well-performer when it comes down to sustained
"high" data transfer rates. This is contrary to many tape drives enduring
the least war and tear when fed with a constant stream of data quickly
enough to not make them stop and start frequently because of buffer
underruns.
I have three 15k drives in my "main" 150 and I would discourage to use a
faster drive/tape combination than DDS3: Stop/start is happening rather
frequently while saving QSYS.LIB, but less so when comparatively large
files (NWSSTG) are to be read from the IFS.
Another 150 of mine has four 6606 drives (5400RPM). I observe likewise
behavior with just a DDS2 drive/cartridge.

Is the tape drive attached to the same controller as the disk?

IIRC, you'd get much better performance with the tape on its own controller.

Charles

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