Okay, checking the datasheet of the HDD, the max. cont. data rate is 180 
MB/s, that's the bottle neck.
I will replace it with a SAS HDD, plugged directly to the HBA.

Wolfgang, can you explain please the context between start-stop mode and 
the serious 
degradation of capacity?

Thanks, Frank

Frank Cherry schrieb am Dienstag, 6. April 2021 um 11:30:35 UTC+2:

> My storage daemon hardware:
>
> Microsemi Adaptec HBA 1100 4i - Speicher-Controller - 4 Sender/Kanal - 
> SATA 6Gb/s / SAS 12Gb/s Low Profile - 1.2 GBps
> Quantum LTO-7 HH - Bandlaufwerk - LTO Ultrium (6 TB / 15 TB) - Ultrium 7 - 
> SAS-2 - intern
> A separate Seagate IronWolf NAS HDD 4TB, SATA 6Gb/s (ST4000VN008) is used 
> for spooling partition only.
>
> The SATA HDD is plugged on the main board's SATA Port. 300 MB/s = 2,4 
> Gb/s, so the 6 Gb/s should be OK.
> Taking a look to the last job: Despooling elapsed time = 03:13:27, 
> Transfer rate = 99.29 M Bytes/second 
>
> Maybe a solution to plug the HDD directly to the SAS controller?
>
> Thanks for help Wolfgang,
> Frank
> wd schrieb am Dienstag, 6. April 2021 um 11:06:09 UTC+2:
>
>> Dear Frank,
>>
>> In message <[email protected]> you wrote:
>> >
>> > I use Ultrium 7 tapes with 6 / 15 TB storage capacity. So I do expect a 
>> > minimum of 6 TB in worst case (without compression).
>> ...
>> > When I now calclulate the present 2.55 TB + 1,2 TB in queue = 3,75 TB, 
>> less 
>> > than 6 TB for LTO-7
>>
>> The spec for LTO 7 gives a sustained data rate of 300 MB/s. Check
>> if your storage daemon can feed the drive with such a rate;
>> otherwise the drive will run in start-stop mode which is slow, causes
>> increased wear on the drive and the tapes, and results in a serious
>> degradation of capacity - as you are seeing here.
>>
>>
>> Best regards,
>>
>> Wolfgang Denk
>>
>> -- 
>> DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
>> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
>> Phone: (+49)-8142-66989-10 <+49%208142%206698910> Fax: 
>> (+49)-8142-66989-80 <+49%208142%206698980> Email: [email protected]
>> Living on Earth may be expensive, but it includes an annual free trip
>> around the Sun.
>>
>

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