I just moved my main amanda server to use software compression instead of 
hardware compression - got tired of banging my head on EOT. The Dump Time 
went through the roof, but it still finished within my expected backup 
window.  I'm impressed with the way amanda continues to perform for me - 
kudos to the developers. Makes the $6k we spent on Veritas look reeeeally 
bad!

I'm slightly baffled at the Tape Time though - it seems to have gone down. 
I expected it to remain about the same, half the data at half the tape 
write speed.

I'm posting my numbers & changes - comments?


Comparison between hardware compression & software compression

Amanda server = RH7.1, PIII 550 Mhz, 256M mem, 80G IDE holding disk
Tape Drive = AIT-2 scsi

Typical results with large backup run using hardware compression:
tape length = 70000 M
netusage  10000 Kbps
maxdumps = 2

Estimate Time (hrs:min)    1:12
Run Time (hrs:min)         9:18
Dump Time (hrs:min)       10:12       7:49       2:23
Output Size (meg)       69757.9    57995.6    11762.3
Original Size (meg)     69757.9    57995.6    11762.3
Avg Compressed Size (%)     --         --         --    (level:#disks ...)
Filesystems Dumped           93         19         74   (1:74)
Avg Dump Rate (k/s)      1944.6     2110.7     1400.9

Tape Time (hrs:min)        3:02       2:16       0:46
Tape Size (meg)         69757.9    57995.6    11762.3
Tape Used (%)             100.0       82.9       17.1   (level:#disks ...)
Filesystems Taped            93         19         74   (1:74)
Avg Tp Write Rate (k/s)  6541.9     7264.8     4388.6


One of the first runs using software compression:
compression = server fast
tape length = 48500 M
netusage  = 10000 Kbps
maxdumps = 2
comprate 0.70 , 0.70

Estimate Time (hrs:min)    1:10
Run Time (hrs:min)         9:54
Dump Time (hrs:min)       39:23      31:53       7:30
Output Size (meg)       27744.5    23489.8     4254.7
Original Size (meg)     56949.0    45437.6    11511.4
Avg Compressed Size (%)    48.7       51.7       37.0   (level:#disks ...)
Filesystems Dumped           91         27         64   (1:64)
Avg Dump Rate (k/s)       200.4      209.6      161.5

Tape Time (hrs:min)        1:25       1:08       0:17
Tape Size (meg)         27744.6    23489.8     4254.8
Tape Used (%)              57.8       48.6        9.2   (level:#disks ...)
Filesystems Taped            91         27         64   (1:64)
Avg Tp Write Rate (k/s)  5560.0     5919.3     4164.3


After a couple weeks, same as above with these changes:
netusage  = 40000 Kbps
maxdumps = 3
holding disk = 140G
reserve = 50

Estimate Time (hrs:min)    1:17
Run Time (hrs:min)        11:29
Dump Time (hrs:min)       27:46      21:57       5:48
Output Size (meg)       42104.5    37389.2     4715.2
Original Size (meg)     71673.5    59705.8    11967.7
Avg Compressed Size (%)    58.7       62.6       39.4   (level:#disks ...)
Filesystems Dumped           91         15         76   (1:76)
Avg Dump Rate (k/s)       431.4      484.5      230.9

Tape Time (hrs:min)        2:02       1:44       0:19
Tape Size (meg)         42104.6    37389.2     4715.3
Tape Used (%)              87.4       77.2       10.2   (level:#disks ...)
Filesystems Taped            91         15         76   (1:76)
Avg Tp Write Rate (k/s)  5873.7     6146.9     4343.1



-----------------------------------------------------
toby bluhm
it support, development systems
philips medical systems, cleveland ohio
tobias.bluhm AT philips DOT com
440-483-5323