Jose Ildefonso Camargo Tolosa wrote:
> Yes, but not every "cheap" hard drive will be able to give you the
> throughput to keep the tape writing continuously, for example, a LTO-4
> drive that I tested a few weeks ago, gave ~100MB/s write speeds, and
> the server that had it attached only went up to 70MB/s hard drive read
> speed (sequential).
> 
> So, I decided to use tmpfs, ~ 1.5GB (I only had 2GB available :( ).

I'd go for a tmpfs, memory is cheap nowadays and it goes (tested with dd 
  to /dev/null and from /dev/zero to around 1.000MB/s )* so speed should
be sufficient. We have 50GB of memory in the server, using ramfs, so it
grows dynamically. 4 concurrent jobs with a job-size-spool limit of 8GB
each.

Even if your harddrive delivers 100MB/s in sequential read/writes. I'm
quite sure you wont see these rates in when running Concurrent Jobs to
the drive. If it isn't some raid with lots of spindelse it'll drop.

The LTO3 drives we're using eats data in the range from 60MB/s to
100MB/s on this setup. The difference probably comes from differnet
compression ratios. Given these "disk"-numbers there is only bacula
preventing the system from obtaining tape-speed, so I expect this is the
the tape-speed-numbers of the LTO3 drives. Hmmm. I ought to try with dd
to a tape to see what that gives.



*
root@bacula:/nfs/home/jk# dd if=/dev/zero of=/z/bacula-spool/testfile 
count=10000 bs=1M
10000+0 records in
10000+0 records out
10485760000 bytes (10 GB) copied, 9.45594 s, 1.1 GB/s
root@bacula:/nfs/home/jk# dd of=/dev/null if=/z/bacula-spool/testfile bs=1M
10000+0 records in
10000+0 records out
10485760000 bytes (10 GB) copied, 13.6342 s, 769 MB/s

-- 
Jesper Krogh

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