Resolving a SCSI Timing Problem

I connected Promise Technology's UltraTrak RM8000 RAID controller to an Ultra320 Adaptec SCSI Card 29320LP-R on my Dell PowerEdge 1650 server, but now the boot cycle takes nearly 8 minutes to get past the 29320LP-R BIOS's SCSI POST stage. I can't live with a 10-minute boot cycle. What's causing this delay?

I'd bet on some sort of SCSI timing problem being the culprit. The 29320LP-R is backward-compatible with Ultra160 devices such as the RM8000 but is much pickier about SCSI timing than standard Ultra160 SCSI cards are. Therefore, timing conflicts can arise on the SCSI-to-ATA backplane between the 29320LP-R and the RM8000. You can try several things to resolve this problem.

First, make sure that you've set the 29320LP-R's termination correctly and that the SCSI cable is in good working order. Next, try disabling the BIOS or BIOS scan for the RM8000's SCSI ID. (This step won't affect the RM8000's performance unless you boot from that device.) To disable BIOS, access the 29320LP-R's SCSISelect configuration utility by pressing Ctrl+A when prompted during the boot process. Go to the Advanced Configuration Settings menu, scroll to find the BIOS Support for Int 13 Extensions option, and set the option to Disabled. To disable the BIOS scan for all devices, change Include in Bios Scan to No under the Advanced Configuration Settings menu. To disable the BIOS scan for the RM8000 only, go to the SCSISelect utility's SCSI Device Configuration menu and change Include in Bios Scan to No for the RM8000's SCSI ID.

Selectively disabling some performance-boosting 29320LP-R options—Domain Validation, Packetized SCSI, and Quick Arbitration and Selection (QAS)—might also improve the time necessary to complete a BIOS scan. The 29320LP-R uses Domain Validation to ensure that attached devices can operate at Ultra320 speed; if a device can't operate at this speed, the 29320LP-R attempts to negotiate a lower speed (e.g., Ultra160). Packetized SCSI is designed to minimize SCSI command overhead and to permit multiple SCSI commands to be transferred over one connection (as opposed to earlier SCSI versions' one command-per-connection limit). QAS reduces some types of overhead and maximizes bus usage. To disable Domain Validation, go to the Advanced Configuration Settings menu and set the Domain Validation option to Disabled. Packetized SCSI and QAS are both disabled from the same location in the host adapter BIOS; go to the SCSI Device Configuration menu and scroll to find each option, then set the options to Disabled for the RM8000's SCSI ID.

If none of these options work, I recommend that you contact Promise or Adaptec and ask whether they have any other suggestions. And don't give up hope: Your problem and others like it will soon disappear thanks to Serial ATA (SATA) and Serial Attached SCSI. The soon-to-arrive Serial Attached SCSI has obvious advantages, including the ability to intermix with SATA on a common bus and cables. Serial Attached SCSI is supposed to have a possible bus speed of 1.5Gbps—that's no typo—and be able to address up to 16,256 devices per port.

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.