Quote:
Originally Posted by
m_raheelahmed
But let me inform you our uncompressed total data size is 1350 GB & when we compress the the data files it will become around 200 GB. So with the the help of compress we are able to hold 5-6 days data in a 1400 GB filesystem which will be backed up on cartridge once in a week. It is also save our storage space for not holding uncompressed data which is huge in size.
Some things to clarify: you can compress a file only once. If you use the utility "compress" (or "gzip", "bzip2" or any other packing program), you have compressed it once, using some CPU time to do so. If you want to restore it you will need CPU time too to uncompress it.
If you use the hardware compression, on the other hand, you will still compress it (and about the same ratio as with "compress"), but use no CPU time to do so. The same, when you restore it.
The size data for the LTO5 tape are pure estimations. OK, 1500GB of uncompressed size is a fact, but "3000GB compressed" simply means: we estimate that our average packing rate will be 1:2, regardless of what is thrown in the drives way, so we say it has 1500 x 2 = 3000GB of compressed capacity. In reality the compression ratio one really achieves varies widely, depending on what a file contains. Picture data like bitmaps usually can easily be compressed by a factor of 1:10, the same with DB-files, while executable files give considerably lower ratios, typically ~1:2 with a LZ78-based algorithm.
That means: if you use solely hardware compression will put you in about the same situation as now or as using software compression (the "compress" utility) alone. Everything else is just a waste of resources, because in your current situation the software compression does all the work and the hardware compression achieves most likely absolutely nothing.
I hope this helps.
bakunin