Re: [Bacula-users] multiple concurrent tape jobs

Hello Dan and Josh,

Sorry, I totally misunderstood the situation here.

It seems to me that data spooling is useful to avoid the tape library be waiting for data from various slow clients.

I think the LTO-4 drive (120 MB/s full height) write speed and 1GB network will be the bottleneck. If you could use both drives for writing, then they would be waiting for data if you have a 1GB network (125 MB/s) and data coming from only one source (the SD with the original disk volume backups). Maybe fast disks (or disk arrays) and both hosts using NIC bonding or 10GB network there would be a gain in performance using concurrent copy jobs.

The local SSD for data spooling seems to me will bring you no gain.

Best regards,

Ana

On Tue, Feb 9, 2016 at 2:30 PM, Josh Fisher <jfisher AT pvct DOT com> wrote:

On 2/8/2016 5:42 PM, Dan Langille wrote:

Hello,

I am working with an LTO-4 tape library. It has two drives but I plan to write to only one for backups.

I will backup to disk first, on another SD. Later, I will copy the jobs to the tape library on this new SD

which is on another server. The copy jobs will be spooled to local SSD before being written to tape.

re http://bacula-users.narkive.com/QRkTVfEz/typical-tape-write-performance

Now what I'm thinking of is streaming multiple concurrent jobs to a single drive

Are the two servers on a 10G or better network? Unless the disk subsystem on the other SD is slow, it will likely stream close to the 1G max of 125 MB/s, since it will be essentially sequential reads. I'm not convinced that concurrency will gain anything.
.

Sure, downside on restore is interleaving of blocks....

I don't see any downsides to going down this path. I have yet to run any copy jobs to the new library,

but it may be ready this week.

Comments?

--

Dan Langille - BSDCan / PGCon

dan AT langille DOT org

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