Hi,
29.09.2008 08:06, Zhang Weiwu wrote:
> Hello. Before getting familiar with bacula I first tried to get familiar
> with tapes. I never used taps before but since I got involved in a job
> related to backup I think I should be familiar with every common
> technology about backup, to give me a good overview to start my work.
Good idea.
> In the office we have Sun DDS-3 driver,
Well, DDS is often called WORN - Write Once Read Never :-)
Compared to other tape technology, DDS is really unreliable. I guess
most people here would agree with this statement.
> from what I see it looks pretty
> new, not heavily used. I bought some new HB DDS-3 tapes (12G) and try
> backup a 10GB directory with simple tar, after cleaned the driver first.
>
> # tar cvf /dev/st0 directory
>
> backup was successful. But try to read from tape was difficult.
>
> # pv < /dev/st0 > /dev/null
>
> For 2 times I got "input / output" error in somewhere close to the first
> 11MB of data. After cleaning the driver again this error is gone. Then I
> got the following error at about 4GB:
>
> pv: (stdin): read failed: cannot allocate memory
I don't know what pv is or how it works, but to know what happens on
the SCSI layer of your tests, a look into the system log might reveal
something.
> When this error take place it's no longer possible to "control" the tape
> driver: re-run the command gives the same error at about 4MB. "eject
> /dev/st0" doesn't work any longer. If I want the tape ejected I have to
> reboot the machine and re-issue eject command.
>
> Since this is the first time I touch the tape driver, can someone tell
> me if this looks like a hardware problem,
Looks like hardware to me - it could even be a SCSI problem, like bad
cabling, incorrect termination, or wrong settings somewhere.
> or is it in general tapes are
> not reliable
My own experience is that LTO, AIT, DLT, SDLT and QIC tape
technologies are quite robust.
I'm actually using DDS drives and tapes, but only for non-critical
data - mainly as a playground for Bacula.
> and tends to have error, or configuration of the device, or
> is the kernel not compatible with the device? I think this is a bit OT
> because I still couldn't manage to run bacula on it yet, but also I
> don't know where to ask such questions, doesn't seems to exist a "linux
> tape mailing list".
I think you should first check your system logs, and if there are any
hardware related errors fix those.
Then, go to ebay and buy a used DLT drive and some new tapes and
you've go a much more reliable - and still inexpensive - platform for
some tests.
If the current capacity of your DDS stuff is ok for you, used DLT
hardware even makes a reasonable production setup - just buy two or
more drives so you can quickly exchange failing hardware.
If you need more capacity, and have some money available, I'd
recommend to consider buying something LTO based.
Arno
> Best regards
>
--
Arno Lehmann
IT-Service Lehmann
Sandstr. 6, 49080 Osnabrück
www.its-lehmann.de
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