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Backup on Tape with Data Protector 6.0

Backup on Tape with Data Protector 6.0

(OP)
hello guys.
I'm using Data Protector 6.0 with Win2003 as Cell Manager. One of my Disk Agent is a ML4048 tape library. I'm using a LTO-3 tape (800GB) but after scaning and formatting before importing to a media pool, DP shows that only 400GB is available on the tape. Is it a problem ? If yes how can I solve it? Is it safe to write over 400GB since the tape capacity is 800GB?
Thank you.

RE: Backup on Tape with Data Protector 6.0

Hiya,

The 800GB is the compressed capacity (assuming 2:1 compression)- the raw capacity of the media is 400GB and are as such the basis of the available space on the media.

It is safe to pass the 400GB marker on the media, however this will only be possible if compression is enabled.

Good luck,
Jesper

RE: Backup on Tape with Data Protector 6.0

(OP)
Jesper,
  Thank you for your prompt answer....Sorry if my question looks dummy (I'm new to DP and Tape backup) but compression needs to be enabled from the tape,from DP or from both ?! Besides, how can I check if compression is enabled from a side or another ?

RE: Backup on Tape with Data Protector 6.0

Most drives will have compression enabled by default and is the easiest way to achieve compression. The normal assumption regarding compression is usually, that for normal operating environments hardware compression is the way to go. Software compression should only be selected if your backups are traveling through a slow WAN link, to 'limit' the amount of data you are pushing through this narrow pipe.

You should be able to ensure that hardware compression is enabled by browsing to the drive properties tab for the individual drive(s) - there should be a tickbox somewhere that controls the setting. It used to be determined by jumper settings on the device itself, but is now controlled by the drive firmware and should be enabled by default.

If you are choosing SW compression, the compression will be performed on the host before data is transmitted to the drive/media agent thus sparking heavy CPU usage on that host. For hardware compression, the actual compression happens when the data reaches the drive buffer where it's compressed before written to the physical tape.

Just make sure that you don't select both SW and HW compression! It will increase the size when written to the physical tape (HW compression control data added to the already compressed data).

Hope this helps,
Jesper

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