Re: LTO 8 Slow write speeds

Am 08.04.25 um 14:18 schrieb Gilles Van Vlasselaer:
>
> Hi all, I'm having issues with write speeds to our LTO drive. Copy jobs aren't going over 100 MB/sec, and on average it's around 80 MB/sec.
>
> Using btape speed I was benchmarking the performance on different tapes (HW compression on/off, HW encryption on/off), and it reached 180-220 MB/sec, depending on the test. Still, it's nowhere near the theoretical maximum of the LTO 8 specification. But even reaching the benchmark speeds would mean that our job copy time would be halved.
>
> Our Storage Daemon stores all full and incremental backups on a file volume. This volume resides on a ZFS pool. I've also benchmarked the ZFS pool, and it easily reads continuously over 300 MB/sec. Once a month, we issue a Copy Job to the LTO 8 tape.
>
> Bacula DIR and SD run on the same machine, with a Quantum LTO-8 HH drive, using Quantum MR-L8MQN-01 tapes.
>
>
> Am I'm missing some important properties in the resources? Any help is appreciated.
>
> - Gilles
>
>

Hi Gilles,

Your Maximum File Size ist too small. If you assume 300MB/sec the tape would stop every 5000/300 seconds to write an EOF mark. That cannot be fast. Please try at least the amount of data for writing 3 minutes sustained (Maximum File Size = 54GB).
Be aware that you have to wait at least for one complete block to be read if you are doing a restore. (3 minutes again in our example). What size are your file volumes?

Best regards, Udo

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