tape compression

[vu pham]

Bill Campbell wrote:
> On Wed, Feb 27, 2008, Vu Pham wrote:
>> My Linux server has a tape drive SDLT320, which is supposed to be able 
>> to store 320Gb data with compression.
> 
> Caveat emptor.
> 
> The numbers claimed for tape compressed capacities are generally
> bogus, assuming 50% compression.  This can be very optimistic,
> depending on the type of files being written.  I've never really
> trusted tape drive's hardware compression, preferring to use
> smart backup software which handle the compression themselves and
> keep track of the tape capacity.
> 
> Programs such as BackupEdge and Lone Tar do file by file
> compresssion, and don't try to compress files that are already
> compressed as attempting to further compress a compressed file
> may well result in a file that's larger than the original.

Bill, thanks for the info. I know the hardware compression is not always 
effective, but I think it could do something like 20%-30% for 
comppresible files. In my case, it looks like there is no compression at 
all, or just 5%, despite the fact that most of the files are text and 
doc files.

I am going to try the software you mentioned.

Thanks,

Vu