dmesg output not as expected

[Dan Langille]

> 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?

— 
Dan Langille
http://langille.org/