Copy BRU LTO tapes using Cache-a

[Tim Jones]

Simple answer, Nope. But, that’s not due to any issue with the BRU format on tape, just that the Cache-A unit doesn’t offer that type of functionality without Cache-A making changes and including a raw-copy function.

However, you can use the “tapecopy” tool included in BRU PE to create copies so long as you have two non-Cache-A tape drives.

Tim
—
Tim Jones
CTO – TOLIS Group, Inc.
https://www.productionbackup.com
BRU … because it’s the RESTORE that matters!

[Tom Goldberg]

Hi Shannon,

You Cache-A system supports the open formats of tar and LTFS. I’m sorry to advise that we do not read or write any proprietary tape formats.

Bru tapes can only be used with Bru software.

Regards,
Tom

Tom Goldberg
Cache-A Corporation
433 Park Point Drive #285
Golden, CO 80401
mailto:tom.goldberg@cache-a.com
https://cache-a.com

[Tim Jones]

Tom is correct in that the Cache-A devices are not able to clone a BRU tape (or any other tape format, for that matter), but copying a tape is not specific to the format of the data written if the tools required are included in the host OS. This is where the Cache-A limitation occurs, not in the fact that the tape was written in BRU format (so please ignore that attempt at playing the proprietary card here).

If the Cache-A host environment included raw tape access capabilities, it could easily be used to duplicate a BRU (or any other tape) so long as 2 similar tape drives were attached.

Tim
—
Tim Jones
CTO – TOLIS Group, Inc.
https://www.productionbackup.com
BRU … because it’s the RESTORE that matters!

[Tom Goldberg]

[Tim Jones] “Cache-A devices are not able to clone a BRU tape (or any other tape format, for that matter)”

Cache-A devices can in fact quickly and easily clone any legal LTFS tape and Cache-A tar tapes.

Tom Goldberg
Cache-A Corporation
433 Park Point Drive #285
Golden, CO 80401
mailto:tom.goldberg@cache-a.com
https://cache-a.com

[Tim Jones]

In that case, the same logic could be applied to cloning BRU tapes, or CPIO tapes, or Retrospect Tapes, or MTF tapes (CA, Symantec, etc.) …

#!/bin/sh
# Free and Open Source script to copy tapes between 2 drives
# written by probably hundreds of Unix system operators over the past 30 years

EOFDETECTED=0
mt -f /dev/nst0 stopt scsi2log can-bsr async
mt -f /dev/nst1 stopt scsi2log can-bsr async
while [ ! EOFDETECTED ]
do

dd if=/dev/nst0 of=/dev/nst1 bs=TAPEBLOCKSIZE conv=sync
EOFDETECTED=$?

done

Of course, for LTFS or CA tapes, you need to remember to check for multiple partitions and partition the destination tape properly.

Works every time so long as you know what block size the tape was created using and that you’ve mapped out the filemarks so that you know how many times to run the operation to get all of the sets on the tape (although that while loop gets it almost every time).

Tim
—
Tim Jones
CTO – TOLIS Group, Inc.
https://www.productionbackup.com
BRU … because it’s the RESTORE that matters!

[Tom Goldberg]

Indeed, that should work if you are comfortable with command line operations.

[Tim Jones] “for LTFS or CA tapes, you need to remember to check for multiple partitions”
Cache-A tar tapes are aways only single partition like any tar tape. LTFS volumes are always 2 partitions, partition 0 for the file system indices, and partition 1 for the data.

[Tim Jones] “so long as you know what block size the tape was created”
Cache-A block size is 300, LTFS block size is 512.

…but I would never bother using that script for cloning LTFS or Cache-A tar tapes as we have a perfectly good user interface that does that for you.

The one critical piece of information you did not provide Tim, is what is the Bru block size?

Tom Goldberg
Cache-A Corporation
433 Park Point Drive #285
Golden, CO 80401
mailto:tom.goldberg@cache-a.com
https://cache-a.com

[Tim Jones]

[TG] – …but I would never bother using that script for cloning LTFS or Cache-A tar tapes as we have a perfectly good user interface that does that for you.

Except that script was simply an example of how you at Cache-A could implement such an interface to perform the cloning. The type of UI that you expose to the end user is totally up to you, so please don’t imply that using a script is a bad thing. I’m sure that under the hood, the Cache-A platform uses a plethora of scripts to accomplish what you do.

Also, the magic numbers that you mention are YOUR choices – also the 300 number for a Cache-A tar tape is actually 300 tar blocks or 150KiB and the LTFS 512 number is 512KiB. These are important details. Also, both tar and LTFS can use other block sizes depending on who makes the tapes. And, as we found out with BRU – described below – those Cache-A defaults may provide the most efficient I/O for one type of data, but definitely not for others.

The BRU block size varies depending on the user’s data needs and archival device type. We learned long ago that I/O block sizes were not a one size fits all number. You may have tapes that are written at 32k aimed at business data (emails, documents) where files are measured in kilobytes or small megabytes, database backups where block sizes ranging from 64k to 512k are fastest, and finally media where block sizes of 1MB, 2MB, or up to 16MB are the most efficient.

However, unlike LTFS, TAR, and CPIO, BRU archives contain the block size information in the archive header and BRU can be given this information readily using our tapectl tool on OS X and Windows and the system log tools on other Unix/Linux platforms. This is just one more implementation detail that allows BRU archives to be TRULY cross platform with no prior knowledge of the environment where an archive was created.

Tim
—
Tim Jones
CTO – TOLIS Group, Inc.
https://www.productionbackup.com
BRU … because it’s the RESTORE that matters!

[Tom Goldberg]

[Tim Jones] “don’t imply that using a script is a bad thing”
Of course not, just not the most convenient route if there is a button to do the same thing.

[Tim Jones] “BRU archives contain the block size information in the archive header “
So in addition to your script, for Shannon and other’s benefit, what command(s) should someone on a Linux system use to get that value?

Tom Goldberg
Cache-A Corporation
433 Park Point Drive #285
Golden, CO 80401
mailto:tom.goldberg@cache-a.com
https://cache-a.com