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#1
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bad readable DLT tape
Hi,
I have a DLT tape which is cannot be read efficiently anymore. When restoring it using tar the tape drive does not stream, i. e. it permanently spools around, forward, backward, and so on. After hours I get input/output errors. My question: Why does the drive spool around for hours? Assuming that the tape is damaged at some sections, then it should stream normally (without changing the directon all the time) at other sections. What I expected is the tape streaming normally after it has passed the bad sections. But this tape does never stream normally. Why can this be? Thanks Magnus |
#2
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bad readable DLT tape
On 20-Apr-2009, Magnus Warker wrote: I have a DLT tape which is cannot be read efficiently anymore. When restoring it using tar the tape drive does not stream, i. e. it permanently spools around, forward, backward, and so on. After hours I get input/output errors. My question: Why does the drive spool around for hours? Assuming that the tape is damaged at some sections, then it should stream normally (without changing the directon all the time) at other sections. What I expected is the tape streaming normally after it has passed the bad sections. But this tape does never stream normally. Why can this be? Did the drive ever work OK in the system in which you are now using it? If there are read errors, the tape will continuosly "shoe shine" trying to fruitlessly read the data with the erronious block checksum. One bad checksum, and the whole file of many blocks becomes unreadable. Causes, bad storage of the tape, it gradually gets erased, particularly if nor rewound. Print through can occur between layers if not regularly rewound end to end. Then there are physical causes, like tape head azimuth alignment, processors and electronics not fast enough, which is why I asked did it ever work in the same system? It's a bit like trying to view 10 years old or more VHS tapes in a different machine to the one they were recorded on. My old Star Trek tapes recorded wnen the series first aired are almost unreadable now. |
#3
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bad readable DLT tape
Thank you! Yes, it already worked in the same environment.
Reading your post it seems that there could be some chance when totally rewinding the tape. Well, I already tried a mt -f /dev/st0 retension, but the drive does nothing. Should I spent further time in getting the retension to work? Is there any hope? :-) Magnus |
#4
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bad readable DLT tape
Magnus Warker wrote:
Thank you! Yes, it already worked in the same environment. Reading your post it seems that there could be some chance when totally rewinding the tape. Well, I already tried a mt -f /dev/st0 retension, but the drive does nothing. Should I spent further time in getting the retension to work? Is there any hope? :-) I've gotten DDS tapes to read properly after doing a couple of rounds of retension. Never tried with DLT. Give it a shot, can't hurt. Yousuf Khan |
#5
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bad readable DLT tape
Ok, thanks for the hopes! :-)
So why does my drive ignore when I say mt -f /dev/st0 retension? Magnus |
#6
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bad readable DLT tape
In article , Magnus Warker
writes Well, I already tried a mt -f /dev/st0 retension, but the drive does nothing. First of all, if you care about the data on the tape, write protect it using the little slider switch on the front. Retension isn't supported on some drives, DLT being among them. Try mt -f /dev/st0 seod to seek to end of data then rewind. What are the drive and cartridge? DLT III, IIIXT, IV? I assume you're using Linux. If you haven't already, install the mt-st package, copy stinit.def from whereever it's been plonked to /etc, then do a stinit -v. All as root. Examine the output of stinit -v and see if it identifies the drive and configures it. Then try reading your tape again. -- (\__/) (='.'=) Bunny says Windows 7 is Vi$ta reloaded. (")_(") http://imgs.xkcd.com/comics/windows_7.png |
#7
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bad readable DLT tape
Mike Tomlinson wrote:
Retension isn't supported on some drives, DLT being among them. Try mt -f /dev/st0 seod to seek to end of data then rewind. I did this and the tape was rewinded. What are the drive and cartridge? DLT III, IIIXT, IV? It's a DLT IV drive. I assume you're using Linux. Debian Etch. If you haven't already, install the mt-st package, copy stinit.def from whereever it's been plonked to /etc, I had it and stinit.def was already located in /etc. then do a stinit -v. All as root. stinit, processing tape 0 The manufacturer is 'BNCHMARK', product is 'DLT1', and revision '5032'. Warning: No modes in definition for ('', '', ''). Can't find defaults for tape number 0. Initialized 0 tape devices. Examine the output of stinit -v and see if it identifies the drive and configures it. Well, looks good, but what about the warning? Then try reading your tape again. It seems that there is no change. It is still spooling around like hell. Magnus |
#8
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bad readable DLT tape
In article , Magnus Warker
writes It's a DLT IV drive. Are you sure? That's not what the output of stinit -v says. It's a DLT1/VS80 drive. That only supports DLTIV cartridges. DLTIII and IIIXT cartridges are not supported. What cartridge are you using? If it's a DLTiV cartridge, was the cartridge you're using written on that particular drive? IME, DLTIV cartridges are usually written on DLT7000 (35/70GB) drives, and a google suggests that the DLT1 will read tapes written on a DLT4000, but NOT those written on a DLT7000. Is it this drive? http://www.sprague-magnetics.com/library/dlt1ds.pdf stinit, processing tape 0 The manufacturer is 'BNCHMARK', product is 'DLT1', and revision '5032'. Those values are read directly from the drive, and it's claiming to be a Benchmark DLT1. The manual for this is available at http://downloads.quantum.com/dlt1/DLT1InstOpGuide.pdf Warning: No modes in definition for ('', '', ''). Can't find defaults for tape number 0. Initialized 0 tape devices. stinit.def has no entries for the Benchmark DLT1, so it cannot be correctly configured. Your next step is to find a stanza for the DLT1 and copy it to stinit.def. I recommend you read http://downloads.quantum.com/sdlt320/6464215011.pdf Try adding the following to the end of stinit.def and re-running stinit -v. drive-buffering=1 scsi2logical=1 no-wait=0 buffering=0 async-writes=0 read-ahead=1 two-fms=0 auto-lock=0 fast-eom=1 can-bsr=1 noblklimits=0 #BNCHMARK VS80 manufacturer=BNCHMARK model="DLT1" { timeout=180 long-timeout=14400 can-partitions=0 mode1 blocksize=0 density=0x41 compression=0 # VS80 density, compression off mode2 blocksize=0 density=0x41 compression=1 # VS80 density, compression on mode3 blocksize=0 density=0x41 compression=0 # DLT8000 density, compression off mode4 blocksize=0 density=0x41 compression=1 # DLT8000 density, compression on } Watch for line breaks when copying and pasting, and don't omit the final }. You're looking for the line "Initialized 1 tape device" after stinit identifies the Benchmark DLT1. Then try re-reading your tape. -- (\__/) (='.'=) Bunny says Windows 7 is Vi$ta reloaded. (")_(") http://imgs.xkcd.com/comics/windows_7.png |
#9
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bad readable DLT tape
It's a DLT IV drive.
Are you sure? That's not what the output of stinit -v says. It's a DLT1/VS80 drive. That only supports DLTIV cartridges. DLTIII and IIIXT cartridges are not supported. What cartridge are you using? Well, I dealt with these things when I bought the drive and I've forgotten the details of the drive. But I am using DLT IV cardriges all the time and all but this one work fine. If it's a DLTiV cartridge, was the cartridge you're using written on that particular drive? Yes! IME, DLTIV cartridges are usually written on DLT7000 (35/70GB) drives, and a google suggests that the DLT1 will read tapes written on a DLT4000, but NOT those written on a DLT7000. I have about 20 DLT IV cardridges, all of the same type and manufacturer. The bad tape we are talking about is the only one. So I conclude that the drive/tape combination is ok. Is it this drive? http://www.sprague-magnetics.com/library/dlt1ds.pdf No. My drive is an internal drive and occupies one 5.25" slot. stinit.def has no entries for the Benchmark DLT1, so it cannot be correctly configured. This sounds interesting. I wonder, if this is the reason why the cardridge cannot be read correctly, then why doesn't this affect all the other tapes? Try adding the following to the end of stinit.def and re-running stinit -v. Looks better: stinit, processing tape 0 The manufacturer is 'BNCHMARK', product is 'DLT1', and revision '5032'. stinit, processing tape 1 Initialized 1 tape device. Then try re-reading your tape. It is still spooling, but something changed... |
#10
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bad readable DLT tape
It is still spooling, but something changed...
Well, it read about 17 G. This is more than it read ever since I initially wrote this posting. There still were some read errors, but - with your help - the drive went on and read more and more. This result is ok for me. Maybe there are some files that are lost, but the big part is saved. I think I'll say goodbye to tape drives and use mirrored disks instead. Thank you very much Magnus |
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