Hardware Compression on StorageWorks DAT 72 External SCSI

[Samuel Benjamin]

Hi all.

I´m usin this storage drive over Windows 2003 Server and NtBackup. When it get´s about 40GB copied to the tape (dat72 c8010a) a messages appears and say that media is full and need to add new media.

Should be a problem with the hardware compression? Is the hardware compression compatible with 2003 server and ntbackup? I have the latest firmware and drivers.

Thanks for your answers.

[thomasr]

The hardware compression works regardless of OS, and will work with almost any backup application -- the only exception is likely to be when you explicitly disable compression for a particular job or tape device.

The 72GB capacity assumes 2:1 compressible data. The "native" capacity of the tape is 36GB. Your information leads me to believe that your data is actually only about 11% compressible ( (40-36)/36 ).

Many file types are not, or only barely, compressible, such as jpeg, mpeg, powerpoint, encrypted, or already compressed files (.zip, etc.).

One mistake some folks make is to tell the backup application to use "SW compression" or something equivalent.... don't do this, as it will only use lots of CPU, slow down your backup, and prevent the drive from compressing files (in essence, you can't compress already compressed files).

If you're in a situation where you can't, or can't easily, swap tapes, you can do one of four things:
1) Upgrade to an autoloader which will handle tape swapping automatically (unfortunately, not an option with NT backup, which can't control a robot, but the HP autoloaders you'd be considering come with a licensed copy of HP Data Protector Express Single Server Edition, which should do what you need).
2) Purchase a larger-capacity tape drive, such as DAT160 or LTO-2 technologies.
3) Split your backup into two pieces, each of which will fit on a single tape, ensure you switch the tape between jobs; run the jobs when convenient.
4) Perhaps some of the data on that server is static -- never changes, never gets added to? In that case, once that directory has a couple of good backups, exclude that directory from future backups, except for, say, once a month.

Oh, there is also 5): Exclude temp directories, temporary log files, etc. from your backup job and hope to get it small enough to fit on one tape.

[Rajanikant]

Hi,

DAT 72 actual capacity is 36GB Native. Assuming a compression of 2:1,it can go a maximum of 72 GB. The compression of the data is based on a lot of factors like Type of the file, size of the files backed up and so on..

Any thing above 36 GB on a DAT 72 is good and this is not a problem

Regards

Raj