Documentation for Yosemite Backup and Recovery Software Products

Yosemite Technologies Knowledge Base
TID: 001346
Compression Settings And TapeWare
Related Operating Systems Windows, Linux, NetWare, DOS, BSD, Solaris
Related Products Pre TapeWare 6.2, TapeWare 6.2, TapeWare 6.3, TapeWare 7.0
Issue Type Configuration Backup
Last Updated 8/4/2005

Standard compressed capacity (i.e. 20/40 = 20GB Native capacity, 40Gb Compressed
Capacity) of a tape is quoted to be 2:1. Even with compression enabled, though
you probably will not get the estimated 2:1 compression ratio. In the real world
this ratio is rarely achieved.

Yosemite Technologies can only guarantee that you will receive native capacity
on your tapes, as compression is entirely theoretical, and dependent on too many
factors to list here.

Some data can not be compressed any more than it is natively (in its format),
while other data can be compressed to 10% of it's original size. Different tape
drives may say 2:1 compression or 4:1 compression but that is only a theoretical
number, assuming the data can be compressed. The only guarantee is that you
can get the native capacity.

In general practice you normally don't see the rated 2:1 compression ration, and
I personally have never seen anything close to a 4:1 compression in a real
environment.

Poor media condition can cause write errors, the data will then have to be
written again, this also reduces tape capacity - Be sure your media is in good
condition.

If you are using data compression, remember that some files do not compress.
These include (but are not limited to) MPEG, JPEG, PDF, CAD, DIVX, AVI etc. If
your drive has built in hardware compression enabled be sure that you do not
have the backup applications software compression enabled as well. If you are
using software and hardware compression together you are actually reducing the
capacity of the tape by creating larger files and also creating larger CPU
utilization.

The compression ratio depends on the data being backed up and may be nothing if
the data is already in a compressed form. When devices with Hardware
Compression are available software compression becomes a waste of CPU cycles.
The best compression and performance are going to come from hardware compression
performed by the tape device.

Below are the compression choices that you will see in the options tab of the
properties of your back up job.

NONE -

This parameter instructs TapeWare to write all data to the tape in a
decompressed format. If the file is stored on disk in a compressed format, the
file will be decompressed before writing. This option is useful if the device
supports hardware data compression and/or the files are to be restored to a
different operating system.

STANDARD -

This parameter instructs TapeWare to write all data to tape in the TapeWare
compression format. If the file is stored on disk in a compressed format, the
file will be decompressed before being re-compressed by TapeWare. This option is
useful if the tape device does not support hardware data compression and/or the
files are to be restored to a different operating system.

SYSTEM -

This parameter instructs TapeWare to write all data to tape in the same mode it
is stored on disk. If the file is stored on disk in compressed format, TapeWare
will write the data in the hosts' compressed format. If the file is not
compressed on disk, TapeWare will store the file on tape in a non-compressed
format. This option is useful if the hardware does support data compression and
the files are to be restored to the same operating system.

BOTH -

This parameter instructs TapeWare to write all data stored on disk in compressed
format, but those files that are not compressed on disk will be stored in the
TapeWare compression format. This option is useful if the hardware does not
support data compression.

Enabling software compression:
1. Open TapeWare
2. Select the "Backup" tab
3. Right click the backup job
4. Select "Properties"
5. Select the "Options" tab
6. Set the "Compression type" to "Standard"
7. Click OK


Disabling software compression:
1. Open TapeWare
2. Select the "Backup" tab
3. Right click the backup job
4. Select "Properties"
5. Select the "Options" tab
6. Set the "Compression type" to "None"
7. Click OK