PETAL: 3.3.2 Exporting a Tape for Backup Purposes

When a backup copy of a tape has to be exported, the procedure differs from the previous one, because backup copy tapes are not considered part of the volume they have been copied from.

Using this procedure, instead, the Volume Library will always be aware that there’s a copy of that particular tape and will keep information about its offline location.

To check which tape belongs to a volume you can use the command vllsdev using the option ‘-n’.

But when ‘set_id’ is instead used to group the tapes, you’ll see that in addition to the tapes shown before, a third tape with a seq. no. resembling the format x.x will appear.

That is the backup copy of the tape with the same initial number in the sequence, in this example tape 101 is the copy of 21 :

vllsdev -n petal | grep deep2
21a: tdo 2.274 TiB Tape Seq=0 SetName=deep2
22a: tdo 2.274 TiB Tape Seq=1 SetName=deep2

[root@petal-fs-01 ~]# vllsdev petal | grep SetId=da1ebd345ad09e32
21a: tdo 2.274 TiB Tape Seq=0 SetId=da1ebd345ad09e32
22a: tdo 2.274 TiB Tape Seq=1 SetId=da1ebd345ad09e32
101a: tdo 2.274 TiB Tape Seq=0.1 SetId=da1ebd345ad09e32

[root@petal-fs-01 ~]# vlmediausage deep2
[++++++++++++++++++++++++++++++++++++++++++++++++++] Done.
Set deep2: 2 media
No Seq.No Status Location Capacity Used
1 0 Current petal:21 2328GB 0GB 0%
2 1 Empty petal:22 2328GB 0%

Total: 4656GB 0GB

If the copy tape is exported from the set now, before switching the tapes, there will be no mention of its existence, either in the list of all the media within the library or in the list of the tapes belonging to a volume set using the command vlmediausage as shown above.

Instead, by switching the original tape with the copy and then exporting it, you will achieve the following situation:

vladdtoset deep2 petal 101

[root@petal-fs-01 ~]# vlmediausage deep2
[++++++++++++++++++++++++++++++++++++++++++++++++++] Done.
Set deep2: 2 media
No Seq.No Status Location Capacity Used

1 0 Current petal:101 2328GB 0GB 0% 2 1 Empty petal:22 2328GB 0%

Total: 4656GB 0GB

[root@petal-fs-01 ~]# vlexport petal 101
petal: Please remove medium from mailslot when it is open.
Type Enter when ready: Enter
deep2:1 0.1 exported from petal:101.
Please enter offline location [deep2_1_0.1_A00101L6]: Storage_Room

[root@petal-fs-01 ~]# vladdtoset deep2 petal 21

[root@petal-fs-01 ~]# vllsset -v deep2
Use_media=tape,writable Spread=no Quota=4096 Media=2
Restore_fsdb=no Read_only=no Real_sim_mix=no
Make_copy=incremental (00 18,7 * * *), Copies: 1
One copy first, auto allocate medium, limit to 4194304 seconds per copy session
Set_type=tdo (Tape and Disk Object file system)
Verify_write=default (Device may enforce hardware verification)
Cache: Cache_root=/export/cache/deep2-cache
Max_number_of_pages=2048000 (500 GiB)
Page_size=256 Kbytes
Low_primary_capacity=0 ()
High_primary_capacity=1638400 (400 GiB)
Mounted at /export/archive/deep2
1: Online=petal:21 Sequence_number=0 Mounted=a Barcode=[A00021L6] Offloc=[deep2_1_0.1_A00101L6:Storage_Room]
2: Online=petal:22 Sequence_number=1 Mounted=a Barcode=[A00022L6]

In this way the backup copy information and location are stored completely in the Volume Librarian database.

To sum up the procedure:

  • Switch the original tape in the set with the copy using the command vladdtoset ,

  • Export the tape just added with the command vlexport and add the offline location,

  • Add the original copy again to the set with the command vladdtoset.

Now the command vlmediausage will show the situation unchanged, with the same two tapes still assigned to the volume set, 21 and 22. But using the command vllsset with the option ‘verbose’ all the information of the online tapes and the location of the offline tape, along with the barcode label will be displayed and the backup copy tape can be easily tracked among those stored outside the library.

You will notice in the syslog of the QStar software, in ‘/opt/QStar/log/syslog’, the following lines during the execution of the procedure:

INFO deep2: TDO volume 0 (/opt/QStar/dev/petal/rjb101a) added to set
VL: petal, shelf 101: /opt/QStar/dev/petal/rjb101a, set deep2, sequence_number 0 added
INFO Export: Medium 1 from set [deep2]
VL: vl_export: petal:101
INFO deep2: TDO volume 0 (/opt/QStar/dev/petal/rjb21a) added to set
VL: petal, shelf 21: /opt/QStar/dev/petal/rjb21a, set deep2, sequence_number 0 added

This lengthy procedure has been found to be the best practice to assure that at any time, from within the software and using its own commands, the status and the location of any tape can be easily retrieved thus facilitating all the managing operations that keep the PETAL Service running smoothly.

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Topic revision: r2 - 08 Nov 2017 - StuartBorthwick1
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