Ultrium 3 tape drive shoe-shining, 3Mb/s: and it's not the cable

Question

I have a HP 960 Ultrium 3 tape drive. Since I got it, (second hand, £90) I've been experiencing shoe-shining. Writing with tar in Linux, I average about 3Mb/s write speed. I've tried replacing both the SCSI card and the cable now, both of which made no difference at all. A curiuos observation I have made is that the write rate is not consistent. Sometimes it will write for over a minute without shoeshining, but more often, just a few seconds. I've also tried several tapes, different source drives, and even writing from Windows Backup, to no avail.

Can you show your `tar` command line? – ewwhite Jun 23 '12 at 00:03 — ewwhite, Jun 23 '12 at 00:03

score 6 · Accepted Answer · answered Jun 23 '12 at 00:12

Shoe-shining refers to the tape drive stopping and rewinding due to an empty data buffer or inconsistent incoming data stream. This was a problem with older DLT drives. LTO drives shouldn't experience shoeshining. The LTO format/standard was partially designed to eliminate this behavior. HP drives, in particular, have a variable write speed to help reduce this effect. The Ultrium 960 should shift down to 27Mb/s as a minimum streaming speed.

We're missing some of the information that could be helpful in diagnosing the issue...

Tell us about your actual hardware setup. Looking at a local HP Ultrium 960 drive, I'm getting write speeds of ~2,000 Megabytes/minute (33Mb/s) across a mixed data set (with hardware compression ON). This is with an HP ProLiant DL380 G6 server and an HP-branded LSI Ultra 320 SCSI HBA.

What type of server are you connected to? What are its specifications? (RAM, CPU, etc.)
Operating system version and distribution? Kernel version?
How are you connected to the server. Which SCSI card are you using?
Most importantly, what does the disk subsystem in the server look like? Is your server capable of 33MB/s disk reads?

I hadn't thought too much about the disk setup. Now I realise what I was missing. I'm archiving video files direct from an NTFS partition in Linux, and Linux hates NTFS. Sure enough, when I did a test from an ext2 partition, the speed was fast enough to completely avoid shoeshining! If you're interested, it's a low power machine with a 1.5GHz VIA C7 processor and a WD5000AADS (WD Caviar Green) hard drive. I'm using Debian 6.0.5, kernel 2.6.32. Thanks, you have helped me. — mowsala, Jun 23 '12 at 21:06

score 2 · Answer 2 · answered Jun 22 '12 at 22:16

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As you have access to a Windows system, download HP Library and Tape Tools. L&TT can run a wide variety of tests and report things which may be set up incorrectly.

answered Jun 22 '12 at 22:16

hmallett

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HP Library and Tape Tools also run directly on Linux. – ewwhite Jun 22 '12 at 23:52

score 1 · Answer 3 · answered Jun 22 '12 at 21:54

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One thing to try is using a cleaning tape and see if this helps. Otherwise, I am guessing that the write head is broken, creating many write errors that get detected by the verify-after-write functionality.

answered Jun 22 '12 at 21:54

Sven

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score 0 · Answer 4 · answered Jun 22 '12 at 22:28

3Mb/s is slow so there probably is a hardware problem as the other answers suggest. However, even when this is fixed, from a single server (depending on hardware and what you are running) you might have trouble writing to the tape fast enough to prevent shoeshining.

Ultrium 3 tape drive shoe-shining, 3Mb/s: and it's not the cable

4 Answers4