On 5/17/24 06:29, Marco Gaiarin wrote:
I'm still fiddling with LTO9 and backup performances; finally i've managed to test a shiny new server with an LTO9 tape (library indeed, but...) and i can reach with 'btape test' 300MB/s, that is pretty cool, even if IBM specification say that the tape could perform 400 MB/s. Also, following suggestion, i'm using spooling to prevent tape to spin up&down; but this clearly 'doubles' the backup time... there's some way to do spooling in parallel? EG, while creating the next spool file, bacula write to tape the current one?
Not for a single job. When the storage daemon is writing a job's spooled data to tape, the client must wait. However, if multiple jobs are running in parallel, then the other jobs will continue to spool their data while one job is despooling to tape.
It is not clear that spooling doubles the backup time. That would only be true if the client is able to supply data at 300 MB/s, or if multiple clients running in parallel can supply a cumulative stream of data at 300 MB/s. Even then, i am skeptical that LTO9 is possible without spooling.
Anyway, i'm hit another trouble. Seems that creating the spool file took an insane amount of time: source to backup are complex dirs, with millions of files. Filesystem is ZFS. 'insane amount' means that having a despool performance of 300MB/s, i'm a overral backup performance of 40MB/s...
It depends greatly on the client, the network, and the type of job. Only full jobs will supply a somewhat continuous stream of data. Client performance is also a factor. Is the client busy while being backed up? How busy is the network?
At the end of data despooling, the attributes are despooled and written to the database, so that is also a part of the overall backup performance. Check the performance of the database writes.
How can i do to improve the spooling performance? What factors impact more? Thanks.
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