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Tape Libraries and Drives
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2 in 2/20

Dmitry Melekhov_2
Frequent Advisor

2 in 2/20


How can I use 2 mechanisms in 2/20
or 2/40? Is it possible to do striping
(something like raid0) for better performance?
Or I can use 2 machinisms for mirroring
written info on two tapes?
Is it possible to use mc in HP-UX
to control this libraries?
btw, is 2/20 supported on Linux?
Eric de Lange_2
Respected Contributor

Re: 2 in 2/20


The 2/20 has 2 slots for DLT or Ultrium drives (the 4/40 has 4). You can configure RAIT (redundant aaray of inexpensive (..) tapedrives) on this unit but you will have to use software that is able to drive that process as most operating systems don't have that functionality natively.

On HP-UX you can use mc to control the library controller.

best regards,


ps. Most linux distributions will support the DLT drives natively. To drive the Library controller in Linux you will have to use an equivalent of mc for Linux. Not sure if mtx ( will do that job though.
Joseph T. Wyckoff
Honored Contributor

Re: 2 in 2/20

Omniback - HP's enterprise tape backup software, which I support, does something a little bit like striping... it is not truly striping - and many customers would like to make it better... but in many respects it is probably something that would meet your needs.

Omniback uses a 'disk agent' for every mounted filesystem that you wish to backup. As many as 5 disk agents can be writing to a media agent (tape drive) at the same time, so the tape drive may be kept streaming.

You may also backup to several tape drives. There is a list of disk agents 'pending' - not yet started - which will backup to which ever tape drive may become available.

The limit that people complain about... an object (filesystem) will only go to ONE TAPE DRIVE - it is NOT STRIPED ACROSS SEVERAL DRIVES - and so is not truly RAID.

If you know you have one file system that is truly length, you can break it up into several logical parts using EXCLUDE / INCLUDE sorts of operations... backup the same drive twice - once with /dir1 and /dir2 excluded and once with /dir3 and dir4 excluded...

In that case, obviously, you are providing the load balancing... but it is certainly feasible.

Of course there may be hidden issues. On the NT platform, for example, St. Bernards (and HP's) Open File Manager (OFM) only expects one copy of Omniback per filesystem... and can error if two agents are running against the same filesystem.

Also, such manual balancing is not 'free' - that is it is not twice as fast to use two agents, their is some overhead.

Similar tweaks probably apply to our competitors as well.

Good Luck.
Omniback and NT problems? double check name resolution, DNS/HOSTS...