Re: LTO 8 Slow write speeds

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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