Compressed v.s Non-compressed RMAN Backup

Recently I performed several tests to compare the RMAN compressed v.s non-compressed backup and see how much disk space v.s duration ratios.  In my test cases, I backed up two tablespaces.  One tablespace ENDORSE_008 contain text data, and ENDORSE_IMG contains images/PDF documents with CLOB data type.  I found the following interesting things:

ENDORSE_008  --Data / text tablespace:  Based on the test case below, if your database does not have a lot of BLOG/CLOB data, it may be a good idea to backup the database using compressed backup set.  It save a lot of disk space as the ratio is very high (at least 1:8) compare with the time it takes to backup with non-compressed mode.




Non-compression                                   Compression
Tablespace:  ENDORSE_008           
Size:  4GB                                                   4GB
Backup size:  4GB                                   500 MB (about 1:8 ratio disk space)
Duration:  25 seconds                          36 seconds




RMAN> run {
2> allocate channel d1 type disk;
3> allocate channel d2 type disk;
4> allocate channel d3 type disk;
5> allocate channel d4 type disk;
6> backup tablespace ENDORSE_008 format '/u01/oracle/admin/ENDORSE/bkups/ENDORSE_ro_endorse_xml_q42008_%s_%p';
7> release channel d1;
8> release channel d2;
9> release channel d3;
10> release channel d4;
11> }