Questions[tapedrive](server)

I have an HP StorageWorks Ultrium 1840 LTO-4 external tape drive attached to a machine running Ubuntu 18.04.4 LTS (kernel 4.15.0-99-generic) using an LSI20320IE PCI-X x4 SCSI adaptor with a VHDCI to HD cable.

Writing to the tape drive is slow and involves a lot of shoe-shining. It maxes out at about 36MB/s. That is an order of magnitude slower than it should be capable of.

I have tried connecting the tape drive to an older machine using an Adaptec 29160 PCI SCSI adaptor and an HD to HD cable. The write speed of the tape drive was pretty much exactly the same (36MB/s).

The hard drives are usually able to transfer data between each other in excess of 150MB/s. But just to check that it wasn't a hard drive or SATA bus limitation, I fed the tape drive from /dev/urandom via buffer and it was still maxing out at about 36MB/s.

I suspect the problem is either with the tape drive itself or at OS level, not the SCSI adaptor or cable. Perhaps there is an mt command to change a setting on the tape drive. How can I diagnose and fix the problem?

Edit: The HP L&TT diagnostic test produces the following output:

    - Firmware rev B56D is out-of-date for Ultrium 4-SCSI as of Thu May 26 19:00:00 2011; update to rev B63D.
    - Rule 19.0 (Performance & Config./Scsi configuration):
    - The current SCSI configuration is likely to be limiting the performance of the drive.
    - Please check that your HBA is the correct type for the drive and that the cabling is good.
    - Current SCSI configuration: narrow   Recommended: wide
    - Current SCSI transfer rate limited to: 40 MB/sec.   Recommended: 320 MB/sec. or better
    - There were 20 rules and 141 subrules checked.
    - Device Analysis completed, and warnings have been reported.

So it looks like the adaptor is detecting the link as narrow instead of wide. That would explain the speed problems. But what could cause that?

We have a Exabyte Mammoth-2 tape drive connected to a Solaris 10 box that's currently able to restore any Exabyte media no problem, but we have two other brands of 8mm tape that are shown as "illegal tapes" and ejected by the tape drive itself.

• Maxell HS-8/112
• 3M D8-112

From what I understand the Exabyte Mammoth-2 will only read AME format. However I can't find any information on what would support both the Maxell and 3M tapes (or even what format they are to begin with).

Any help on the matter is greatly appreciated.

I've noticed that most tape drive vendors provide two options: full-height or half-height. The half-height drives are physically smaller and less expensive, yet seem to have identical specifications compared to their full-height peers.

What is the real difference between these drives? If they were really identical in operation, I'm sure that nobody would purchase the more expensive full-height drives, and they would stop being produced.

There are many ways to monitor block device performance: dstat and iostat, heck, even sar will give you data on block device I/O rates. Unfortunately, I don't know of any good spur-of-the-moment tools for monitoring the performance of a character device like a tape drive.

I know there are tools to monitor performance if you remember in advance to do it (pv, dd + SIGUSR1, probably others), but say you're 2 hours into a job that might be 3 hours or 30 hours depending on the performance, and you don't know which it is.

The only thing I can think of is some elaborate use of strace or similar, parsing the output for bytes written, maybe with timestamps. Is there a commonly used tool that I've forgotten or never heard of?

I currently have a QNAP NAS with a raid 5 config (~600gb storage) but don't have a reliable backup solution. I've heard great things about tape backup systems (reliability, durability, etc..).

How can I go about setting up a tape backup system? The tape drives seem very expensive (1k+ for a decent one, more than the price of my NAS). What are the important specs to compare and features to take into consideration?

Edit: Does anyone have links to some good resources? There is a ton of articles, guides, and sites on this subject, not sure where to start.