Re: [Bacula-users] LTO 8 Slow write speeds

[Gilles V. V. <gil...@em...>]

Hi Udo,

> 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).
I'll try this once the current copy job is complete, benchmarking the 
btape speed command using file_size=5 wrote 5GB chunks, which reached 
the 200MB~/sec mark.

> What size are your file volumes? 

Pool Daily -> Incrementals + daily bacula DB dump

+------------+-----------+---------+-----------------+----------+

| volumename | volstatus | enabled | volbytes        | volfiles |

+------------+-----------+---------+-----------------+----------+

| Catalogs   | Used      |       1 | 407,715,205,671 |       94 |

| Daily-13   | Used      |       1 | 953,720,636,816 |      222 |

| Daily-10   | Append    |       1 |  79,824,581,674 |       18 |

| Daily-11   | Used      |       1 | 778,609,282,174 |      181 |

| Daily-12   | Used      |       1 | 573,366,535,214 |      133 |

| Daily-0085 | Used      |       1 | 408,215,876,761 |       95 |

| Daily-0260 | Used      |       1 | 460,077,395,998 |      107 |

+------------+-----------+---------+-----------------+----------+

Pool Weekly -> Full backups

+-------------+-----------+---------+-------------------+----------+

| volumename  | volstatus | enabled | volbytes          | volfiles |

+-------------+-----------+---------+-------------------+----------+

| Weekly-0035 | Used      |       1 | 3,224,557,692,497 |      750 |

| Weekly-0036 | Used      |       1 | 2,323,662,023,874 |      541 |

| Weekly-0037 | Append    |       1 | 5,563,811,862,205 |    1,295 |

| Weekly-0043 | Full      |       1 |               202 |        0 |

+-------------+-----------+---------+-------------------+----------+

Thank you,

- Gilles

On 4/8/25 15:13, Udo Kaune wrote:
> 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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