LTO 8 Slow write speeds

Am 10.04.25 um 13:33 schrieb Gilles Van Vlasselaer:
>
> Hi Udo,
>
> Thanks for your input, with the itdt command I got the following;
>
> Compres- Transfer  Data Size Elapsed  Data Rate
>    able   Size (KB)   (MB)    Time (s)   (MB/s)
> +------+---------+---------+--------+----------+
> | No   | 512     | 29999   | 104.766| 286.342  |
> | No   | 256     | 29999   | 104.386| 287.385  |
> | No   | 128     | 29999   | 114.132| 262.844  |
> | No   | 64      | 29999   | 155.715| 192.654  |
> | Yes  | 512     | 29999   | 76.9336| 389.934  |
> | Yes  | 256     | 29999   | 85.9795| 348.909  |
> | Yes  | 128     | 29999   | 108.639| 276.135  |
> | Yes  | 64      | 29999   | 152.646| 196.526  |
>
> In the Device resource for my LTO drive I've added;
>
> Minimum block size = 256K # Seemed to be optimal
> Maximum blocksize = 512K  # Seemed to be optimal
> Maximum File Size = 29G   # Less start-stops for EOF marks
>
> The Bacula docs defines a default of 64K which seemed to perform 'poorly' for my drive.
>
> Now I'm running a test copy job of 600GB, averaging 210MB/sec and peaking 240MB/sec at time, huge improvement, never heard the drive zoom so hard during writes.
>
> Thank you once again!
>
> - Gilles
>

Hi Gilles,

That's good news. Please leave out the "Minimum Block Size". "Maximum Block Size" defines also the default that will be used. ITDT made up the 29G, you don't need to adhere to them. Even though 1024K Transfer Size is not listed in the ITDT table you should give it a try.
Please reevaluate your spool disk. As you can see in the ITDT table you already need 389MB/sec sustained if data is compressible.

br, Udo

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