I am using an HP Dat72 drive. When I create a job I am enabling hardware compression. Upon reviewing the job log I get a message at the top "Compression is disabled due to hardware data compression". Upon reviewing the job log I see "Total Size (Disk)" and "Total Size (Media)". These numbers are usually very close in MB. My question is: is this the actual size of the data on the media? If so, why isn't compression occurring on the tape?
Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations Mike Lewis on being selected by the Tek-Tips community for having the most helpful posts in the forums last week. Way to Go!
Newbie compression question 1
- Thread starter biffstew
- Start date
davidmichel
Technical User
ARCserve will not let you use both software and hardware compression since it will only increase the data size, can't compress compressed data.
The reason for poor compression is almost always due to the type of data being compressed. For example jpg, mp3, avi, divx, etc. is all compressed data. So as stated above it will not get smaller. Oh and don't forget Windows compression enabled via the file system, and if the data is encrypted prior to compression then there will be no compression. Compression works by taking out repeating patterns and with the above there is none.
The reason for poor compression is almost always due to the type of data being compressed. For example jpg, mp3, avi, divx, etc. is all compressed data. So as stated above it will not get smaller. Oh and don't forget Windows compression enabled via the file system, and if the data is encrypted prior to compression then there will be no compression. Compression works by taking out repeating patterns and with the above there is none.
-
1
- #3
the real compression rate is given on the Arcserve server logs. There is an indication "compression rate.."
"Total Size (Disk)" and "Total Size (Media)" reports the physical volume passed to the drive before compression, not the volume written to the tape by the drive after compression.
I got once in the job logs accurate indication over "Total Size (Media)" really indicating the compressed volume, but never got it a second time, and never got accurate support from CA about it.
"Total Size (Disk)" and "Total Size (Media)" reports the physical volume passed to the drive before compression, not the volume written to the tape by the drive after compression.
I got once in the job logs accurate indication over "Total Size (Media)" really indicating the compressed volume, but never got it a second time, and never got accurate support from CA about it.
- Thread starter
- #4
- Status
Similar threads
- Locked
- Question