SCSI tape problem
 

Hi,
I hope someone can help with this. I'm troubleshooting an Exabyte tape
drive connected to a Transtec machine running Scientific Linux 4.4. The
SCSI controller is an Adaptec 2940. There are no problems in seeing the
tape drive and it seems to respond sensibly to various 'mt' commands
such as 'status', 'rewind', 'eject', and 'weof'. The problem comes when
I try to write a file to a tape with 'tar cf /dev/tape somefile' - the
command never terminates; it can't be killed with CTRL-C or 'kill -9' -
only a reboot will get rid of it. When it's in this state I cannot find
any error messages anywhere but the 'Commands Active' line in the output
from 'cat /proc/scsi/aic7xxx/0' shows '1'.

I should point out that the tape drive does not have a terminator -
when I fitted one the Adaptec BIOS stopped detecting the drive! (Why?)

I'd be grateful for any ideas to try. I've appended some pertinent
system information below:-


[root@xxxxxxx log]# dmesg (ABBREVIATED OUTPUT)
SCSI subsystem initialized
scsi0 : Adaptec AIC7XXX EISA/VLB/PCI SCSI HBA DRIVER, Rev 6.2.36
<Adaptec 2940 Ultra2 SCSI adapter>
aic7890/91: Ultra2 Wide Channel A, SCSI Id=7, 32/253 SCBs

(scsi0:A:0): 5.000MB/s transfers (5.000MHz, offset 11)
Vendor: EXABYTE Model: EXB-85058SQANXR1 Rev: 0808
Type: Sequential-Access ANSI SCSI revision: 02



[root@xxxxxxx log]# lspci -vv (ABBREVIATED OUTPUT)
05:01.0 SCSI storage controller: Adaptec AHA-2940U2/U2W
Subsystem: Adaptec AHA-2940U2W SCSI Controller
Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV+ VGASnoop- ParErr+ Stepping- SERR+ FastB2B-
Status: Cap+ 66Mhz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
Latency: 64 (9750ns min, 6250ns max), Cache Line Size 08
Interrupt: pin A routed to IRQ 145
BIST result: 00
Region 0: I/O ports at 4000 [disabled] [size=256]
Region 1: Memory at e2200000 (64-bit, non-prefetchable) [size=4K]
Capabilities: [dc] Power Management version 1
Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
Status: D0 PME-Enable- DSel=0 DScale=0 PME-



[root@xxxxxxx log]# cat /proc/scsi/scsi
Attached devices:
Host: scsi0 Channel: 00 Id: 00 Lun: 00
Vendor: EXABYTE Model: EXB-85058SQANXR1 Rev: 0808
Type: Sequential-Access ANSI SCSI revision: 02



[root@xxxxxxx log]# cat /proc/scsi/aic7xxx/0
Adaptec AIC7xxx driver version: 6.2.36
Adaptec 2940 Ultra2 SCSI adapter
aic7890/91: Ultra2 Wide Channel A, SCSI Id=7, 32/253 SCBs
Allocated SCBs: 4, SG List Length: 128

Serial EEPROM:
0x03bb 0x03bb 0x03bb 0x03bb 0x03bb 0x03bb 0x03bb 0x03bb
0x03bb 0x03bb 0x03bb 0x03bb 0x03bb 0x03bb 0x03bb 0x03bb
0x18a6 0x1c5d 0x2807 0x0010 0xffff 0xffff 0xffff 0xffff
0xffff 0xffff 0xffff 0xffff 0xffff 0xffff 0xffff 0x98bf

Target 0 Negotiation Settings
User: 80.000MB/s transfers (40.000MHz, offset 127, 16bit)
Goal: 5.000MB/s transfers (5.000MHz, offset 11)
Curr: 5.000MB/s transfers (5.000MHz, offset 11)
Channel A Target 0 Lun 0 Settings
Commands Queued 107
Commands Active 0
Command Openings 1
Max Tagged Openings 0
Device Queue Frozen Count 0
Target 1 Negotiation Settings
User: 80.000MB/s transfers (40.000MHz, offset 127, 16bit)
Target 2 Negotiation Settings
User: 80.000MB/s transfers (40.000MHz, offset 127, 16bit)
Target 3 Negotiation Settings
User: 80.000MB/s transfers (40.000MHz, offset 127, 16bit)
Target 4 Negotiation Settings
User: 80.000MB/s transfers (40.000MHz, offset 127, 16bit)
Target 5 Negotiation Settings
User: 80.000MB/s transfers (40.000MHz, offset 127, 16bit)
Target 6 Negotiation Settings
User: 80.000MB/s transfers (40.000MHz, offset 127, 16bit)
Target 7 Negotiation Settings
User: 80.000MB/s transfers (40.000MHz, offset 127, 16bit)
Target 8 Negotiation Settings
User: 80.000MB/s transfers (40.000MHz, offset 127, 16bit)
Target 9 Negotiation Settings
User: 80.000MB/s transfers (40.000MHz, offset 127, 16bit)
Target 10 Negotiation Settings
User: 80.000MB/s transfers (40.000MHz, offset 127, 16bit)
Target 11 Negotiation Settings
User: 80.000MB/s transfers (40.000MHz, offset 127, 16bit)
Target 12 Negotiation Settings
User: 80.000MB/s transfers (40.000MHz, offset 127, 16bit)
Target 13 Negotiation Settings
User: 80.000MB/s transfers (40.000MHz, offset 127, 16bit)
Target 14 Negotiation Settings
User: 80.000MB/s transfers (40.000MHz, offset 127, 16bit)
Target 15 Negotiation Settings
User: 80.000MB/s transfers (40.000MHz, offset 127, 16bit)

The problem would have appeared to have been a termination problem.
Without a terminator the tar command would eventually timeout after
15 minutes (the default timeout for tape drives). Setting a lower
timeout with 'mt sttimeout 60' confirmed this without having to wait
15 minutes!

I then tried an LSI SCSI card - luckily this allowed the tape drive
to function without being terminated. When I tried the only terminator
I had, I got an error message telling me to check the cable and terminator
and the tape drive would not function. It would appear that the terminator
I had was for a HVD device and not single-ended - I still need to acquire
the correct terminator to test this.