Zitat von Carsten Jensen <tomse AT tomse DOT dk>:
> Sorry for answering again, accidently hit send while not finished
>
> to compare an LTO4 drive with an Ultra320 controller
> I get around 55MB/sec
>
> my guess is that the LTO3 drive should deliver around 30-40MB/sec
> with the right controller (ultra320).
> (pay note to that there usually are 2 models, a fast and slow one, from
> each vendor)
>
> trying to remember back when using a 2940UW host adapter with a UW drive.
> I seem to remember to get around 10MB/sec out of the drive
>
> so 8.8MB/sec does seem like it's what you can get out of the controller.
> (I could remember wrong)
>
> cheers
> Carsten
>
> On 2012-10-18 21:02, Wolfgang Denk wrote:
>> Hello,
>>
>> apologies in advance - this may be a bit off topic, but I guess I find
>> most experts for such a problem on this list...
>>
>>
>> I see very poor performance with HP Ultrium LTO3 drive, which is
>> attached over SCSI to a Linux box (using a Adaptec 2940 Ultra SCSI
>> adapter). It seems I cannot get more than about 8.8 MBytes/s for
>> either writing to or reading from the drive.
>>
>> Looking around, I see this information in /proc/scsi/aic7xxx/3 :
>>
>> ...
>> Target 5 Negotiation Settings
>> User: 40.000MB/s transfers (20.000MHz, offset 127, 16bit)
>> Goal: 10.000MB/s transfers (10.000MHz, offset 15)
>> Curr: 10.000MB/s transfers (10.000MHz, offset 15)
>> Channel A Target 5 Lun 0 Settings
>> Commands Queued 20
>> Commands Active 0
>> Command Openings 1
>> Max Tagged Openings 4
>> Device Queue Frozen Count 0
>> ...
>>
>> Am I understanding this correctly that the SCSI adapter is set to
>> 10 MB/s transfers only? That would certainly expolain the transfer
>> rates I'm observing...
>>
>> Is there any way to tweak these settings in Linux? I alreay checked
>> in the SCSI adapter's BIOS settings, but there are no indications for
>> auch a limitation.
>>
>> [Yes, I am aware that the Adaptec 2940 is not exactly new. But I
>> should get more than 8.8 MB/s out of it, should I not?]
>>
>> Any help welcome. Thanks in advance.
>>
>> Best regards,
>>
>> Wolfgang Denk
>>
Don't go that road. A LTO-3 FH should do around 60..80MByte/sec
without compressable data, if drive compression is used i suspect it
to hit the 100MByte/sec easily. Even if you SCSI controller is a
2940UW or 2940U2W you limit the drive to something around 50% of the
possible speed and "shoe-shining"
(http://de.wikipedia.org/wiki/Shoeshine-Problem) will happen for sure.
Furthermore while in theory the tape drive should negotiate all
possible SCSI variants, some newer devices fall-through if no LVD mode
is possible. I suggest to buy some used U-160 or U-320 card with PCIe
and let your LTO do its job.
Regards
Andreas
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