dmesg output not as expected

[Dan Langille]

> On Jul 28, 2015, at 10:30 PM, David Gwynne <david at gwynne.id.au> wrote:
> 
> 
>> On 29 Jul 2015, at 12:18, Dan Langille <dan at langille.org> wrote:
>> 
>>> 
>>> On Jul 28, 2015, at 1:01 PM, Dan Langille <dan at langille.org> wrote:
>>> 
>>> I wish to move a tape library from one system to another.  Today I moved the cable from one system to another and ran 'camcontrol rescan all'.
>>> 
>>> For sa0, why do I see 80MB/s on the old system vs 40MB/s on the new system?  Is this card related? Slot related?
>>> 
>>> Similarly, ch0 goes from 20MB/s to 3.3MB/s....
>>> 
>>> I was hoping for a speed boost.  :)
>>> 
>>> Some of the camcontrol devlist output includes:
>>> 
>>> <COMPAQ SuperDLT1 5F5F>            at scbus14 target 1 lun 0 (pass11,sa0)
>>> <COMPAQ MSL5000 Series 0520>       at scbus14 target 3 lun 0 (pass12,ch0)
>>> 
>>> This is on the existing system:
>>> 
>>> I *think* this system holds a Symbios Ultra2 32-bit PCI SCSI Adapter SYM8951U
>>> 
>>> Jul 23 13:24:19 knew kernel: sym0: <895> port 0xe000-0xe0ff mem 0xfebeec00-0xfebeecff,0xfebef000-0xfebeffff irq 22 at device 2.0 on pci4
>>> Jul 23 13:24:19 knew kernel: sym0: No NVRAM, ID 7, Fast-40, LVD, parity checking
>>> 
>>> Jul 23 13:24:19 knew kernel: sa0 at sym0 bus 0 scbus7 target 1 lun 0
>>> Jul 23 13:24:19 knew kernel: sa0: <COMPAQ SuperDLT1 5F5F> Removable Sequential Access SCSI-2 device
>>> Jul 23 13:24:19 knew kernel: sa0: Serial Number CXB46H0716
>>> Jul 23 13:24:19 knew kernel: sa0: 80.000MB/s transfers (40.000MHz, offset 31, 16bit)
>>> 
>>> Jul 23 13:24:19 knew kernel: ch0 at sym0 bus 0 scbus7 target 3 lun 0
>>> Jul 23 13:24:19 knew kernel: ch0: <COMPAQ MSL5000 Series 0520> Removable Changer SCSI-2 device
>>> Jul 23 13:24:19 knew kernel: ch0: Serial Number 3G22JJP38S46
>>> Jul 23 13:24:19 knew kernel: ch0: 20.000MB/s transfers (10.000MHz, offset 15, 16bit)
>>> Jul 23 13:24:19 knew kernel: ch0: 25 slots, 1 drive, 1 picker, 1 portal
>>> Jul 23 13:24:19 knew kernel: ch0: quirks=0x2<NO_DVCID>
>>> 
>>> This is the same tape drive on another system:
>>> 
>>> LSI Logic Ultra320 (LSI20320IE) SCSI PCI-E
>>> 
>>> mpt0: <LSILogic 1030 Ultra4 Adapter> port 0x8000-0x80ff mem 0xfb220000-0xfb23ffff,0xfb200000-0xfb21ffff irq 19 at device 8.0 on pci15
>>> mpt0: MPI Version=1.2.14.0
>>> 
>>> Jul 28 16:36:31 varm kernel: sa0 at mpt0 bus 0 scbus14 target 1 lun 0
>>> Jul 28 16:36:31 varm kernel: sa0: <COMPAQ SuperDLT1 5F5F> Removable Sequential Access SCSI-2 device
>>> Jul 28 16:36:31 varm kernel: sa0: Serial Number CXB46H0716
>>> Jul 28 16:36:31 varm kernel: sa0: 40.000MB/s transfers (40.000MHz DT, offset 6)
>>> 
>>> Jul 28 16:37:03 varm kernel: ch0 at mpt0 bus 0 scbus14 target 3 lun 0
>>> Jul 28 16:37:03 varm kernel: ch0: <COMPAQ MSL5000 Series 0520> Removable Changer SCSI-2 device
>>> Jul 28 16:37:03 varm kernel: ch0: Serial Number 3G22JJP38S46
>>> Jul 28 16:37:03 varm kernel: ch0: 3.300MB/s transfers
>>> Jul 28 16:37:03 varm kernel: ch0: 25 slots, 1 drive, 1 picker, 1 portal
>>> Jul 28 16:37:03 varm kernel: ch0: quirks=0x2<NO_DVCID>
>> 
>> After rebooting this server, I see this in /var/run/dmesg.  Why does it change?
>> 
>> ch0 at mpt0 bus 0 scbus14 target 3 lun 0
>> ch0: <COMPAQ MSL5000 Series 0520> Removable Changer SCSI-2 device
>> ch0: Serial Number 3G22JJP38S46
>> ch0: 20.000MB/s transfers (10.000MHz DT, offset 15, 16bit)
>> ch0: 25 slots, 1 drive, 1 picker, 1 portal
>> ch0: quirks=0x2<NO_DVCID>
>> 
>> I was hoping to get more through put on this newer system with a different card.  From what I see, my speed is only half of what it was.
>> 
>> I'm using a PCI-E 3.0 X8 (in X16) slot. Have I missing something?
> 
> technically parallel scsi isn't a hot pluggable medium. rebooting likely lets it settle and negotiate better.
> 
> you probably shouldnt care about the speed you talk to the changer at btw. you're not sending data to the changer device, just commands to move tapes around which are very low bandwidth.

Noted.  However, sa0 went from 80 to 40MB/s...

> did your tape device negotiate faster after the reboot?

I did not notice.  I'll compare soon.

—
Dan Langille
http://langille.org/





-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 971 bytes
Desc: Message signed with OpenPGP using GPGMail
URL: <http://lists.freebsd.org/pipermail/freebsd-scsi/attachments/20150728/26c6a2bf/attachment.bin>