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

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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

On 4/8/25 18:13, Udo Kaune wrote:
> Am 08.04.25 um 16:17 schrieb Gilles Van Vlasselaer:
>>
>> 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 |
>> +-------------+-----------+---------+-------------------+----------+
>>
>>>> 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?
> Please also try to analyse your drive using the latest IBM Tape 
> Diagnostics Tool. Sample output below. Transfer Size (KB) will 
> translate to "Maximum Block Size" in Bacula Device config. Changing 
> this parameter will possibly inhibit restore from your already written 
> tapes. Remember to change it back if you need access to existing backups.
>
> https://www.ibm.com/support/fixcentral/swg/selectFixes?parent=Tape%20drivers%20and%20software&product=ibm/Storage_Tape/IBM+Tape+Diagnostic+Tool+ITDT&release=1.0&platform=Linux&function=all
>
>      IBM Tape Diagnostic Tool Standard Edition  - System Test
>
>    Model           Serial       Fware Result:
>    +--------------+------------+------+ +----------------------+
>    | ULTRIUM-HH6  | 10WT160994 | K4M1 |               | 
> PASSED               |
>    +--------------+------------+------+ +----------------------+
> Code:
>    Compres- Transfer  Data Size Elapsed  Data Rate 
> +----------------------+
>     sible   Size (KB)   (MB)    Time (s)   (MB/s)     | 
> OK                   |
>    +------+---------+---------+--------+----------+ 
> +----------------------+
>    | No   | 1024    | 6250    | 86.106 | 131.983 |
>    | No   | 512     | 6250    | 79.495 | 92.647 |
>    | No   | 256     | 6250    | 80.386 | 92.6353  |   Text Log:
>    | No   | 128     | 6250    | 79.539 | 92.5118  | 
> +----------------------+
>    | No   | 64      | 6250    | 79.595 | 92.3869  |   | 
> 10WT160994.001.txt   |
>    | Yes  | 1024    | 6250    | 21.931 | 392.07   | 
> +----------------------+
>    | Yes  | 512     | 6250    | 21.428 | 376.521 |
>    | Yes  | 256     | 6250    | 20.752 | 392.87   |   Bin Log:
>    | Yes  | 128     | 6250    | 23.14  | 347.029  | 
> +----------------------+
>    | Yes  | 64      | 6250    | 36.571 | 281.224  |   | 
> 10WT160994.001.blz   |
>    +------+---------+---------+--------+----------+ 
> +----------------------+
>
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>
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