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chaining two DLT4000's

Norman Dignard
Regular Advisor

chaining two DLT4000's

We've just ran into a problem with our backups in that it now needs to spool to a 2nd tape. The problem with this is that there's no one around a 4AM to change tapes. We are in the process of getting a LTO library but we're not there yet. In the mean time we do have a 2nd DLT that we can use.

My questions are:
Can I daisy chain the 2nd off the first? Both are in a Smart rack (C4318B). From reading the forum it looks like I can.

Can I bring the 2nd DLT up without a reboot?

How to I configure fbackup to use the second tape once the first fills up? We currently have a cron job to run a script that calls fbackup.

Norm

5 REPLIES
Jean-Luc Oudart
Honored Contributor

Re: chaining two DLT4000's

You can daisy chain tape drives.
You may loose in performance. Saying that DLT4000 aren't that fast.
I was always told to keep my backup devices onto different controlers...

I think in fbackup you can specify more than one output file. But I never tried it.
cf. man pages

Jean-Luc
fiat lux
Joshua Scott
Honored Contributor

Re: chaining two DLT4000's

What's the model number of your drive, C6381A or C6383A?

The transfer rate of the DLT4000 is 1.5MB/s which is substantially slower that a narrow SE (5MB/s) or a narrow Differential (10 MB/s) bus. hooking up the second drive SHOLUD be no problem.

What model is your server, and how are you connected to the drives? Are there any other devices on the SCSI bus? There may be other issues depending on how it is hooked up.

-Josh
What are the chances...
Leif Halvarsson_2
Honored Contributor

Re: chaining two DLT4000's

Hi,
It is not any problem to daisy chain several DLT 4000 on the same SCSI (I have 3 chained myself). fbackup uses the drives sequential so the SCSI bandwith should not be any problem.
Use:

fbackup -f -f ......
Norman Dignard
Regular Advisor

Re: chaining two DLT4000's

The system is a L3000. The DLT's are a C6383A housed in a C4318B rack.

The one DLT is connected via a SCSI DF cable to a C87x Fast Wide Diff and its the only unit on that bus.
Kurt Beyers.
Honored Contributor

Re: chaining two DLT4000's

The easiest workaround will be to create 2 fbackup jobs. One writes to the first DLT and the other to the second DLT.

It is a workaround, but I don't think it is possible to tell fbackup that the second DLT drive must be used when the first tape is full.

Kurt