Bill Arlofski via Bacula-users schrieb am 11.05.23 um 20:45:
On 5/10/23 21:49, Dr. Thorsten Brandau wrote:
Hi
I use an lto-9 drive for backup. I activated hardware compression on
the tape (i think) but all the logs of bacula show a tape change at
18TB which should be the native (uncompressed) capacity. From
experience I would expect a ratio of at last 1:1.2. Is there any way
to make sure to use compression (or as last resort activate software
compression)?
Hello Thorsten,
Of course, with LTO tape drives, you always want to enable hardware
compression and disable software compression in Bacula.
How that is set on your specific drive(s) I do not know. :)
Bacula will just write until it gets an EOT (end of tape) from the
tape drive, so the compression you will see is dependent on your dataset.
Some tips:
In your Director's configuration for the Storage resource which points
to the SD's Tape drive (or library with multiple drives), you should set
`AllowCompression = no`
This will tell the FDs to not try to compress data before sending it
to the SD when using this Storage resource in a job, even if you have
a `compression = (lzo|gzip|zstd)` in your fileset.
For jobs using this Storage, if compression in enabled for the fileset
in use, you will see a harmless info log entry in the job logs telling
you that "compression is not allowed for this storage device". (or
similar)
I prefer to enable/disable this in the Director's Storage resource and
always enable compression in my filesets so that the same job and
fileset, when using a different Director Storage that allows
compression, it will automatically "Just Work"™
P.S. You can enable/disable compression in the SD's Devices, but I
prefer to set it at what I would call the beginning of the chain in
the Director's Storage resource.
Home some of this is helpful,
Bill
Hi Bill
I decided to use the softwarecompression instead, as this actually
compresses the files. At last it means 1.4:1 for me, which is a lot
better than uncompressed backup (LTO9 tapes are very expensive...). Any
other setting did not work and from the change rates I have seen the
drive did not compress the data (in the autochanger). I have no idea if
it is a problem of the autochanger or not. On the other hand, that also
reduced my total backuptime quite a bit as less data had to be written
and cached...
Cheers
T
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