Backup tape compression
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pufferfish
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Published on 2012-09-06T12:55:01Z
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2012/09/06
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What things should I check to confirm that compression is actually happening on our tape backup system? Although the tapes are marked as 200G/520G (native/compressed) capacity, they seem to fill up before the 200G mark (some less than 100G).
I'm using - Sony AIT-4 tape autochanger - Sony SDX4-200C (AIT-4) tapes - Ubuntu Lucid - Bacula
I've tried checking hardware compression with: tapeinfo -f /dev/nst0, which gives
Product Type: Tape Drive
Vendor ID: 'SONY '
Product ID: 'SDX-900V '
Revision: '0102'
Attached Changer API: No
SerialNumber: '0001000036'
MinBlock: 2
MaxBlock: 8388608
SCSI ID: 1
SCSI LUN: 0
Ready: yes
BufferedMode: yes
Medium Type: Not Loaded
Density Code: 0x33
BlockSize: 0
DataCompEnabled: yes
DataCompCapable: yes
DataDeCompEnabled: yes
CompType: 0x3
DeCompType: 0x3
BOP: yes
Block Position: 0
Partition 0 Remaining Kbytes: 201778000
Partition 0 Size in Kbytes: 201779000
ActivePartition: 0
EarlyWarningSize: 0
NumPartitions: 0
MaxPartitions: 0
... so I presume it's on.
Notes:
- The Bacula documentation says hardware compression needs to be enable with "system tools such as mt"
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