IBM SCSI-2 RAID Controller, SCSI-2 Fast/Wide Streaming-RAID Adapter/A and Mylex DAC960PD-Ultra, DAC960PD/DAC960P, DAC960PL, DAC960E Controllers

Preconfiguration Information

• The choice of SCSI target ID numbers is limited. Assuming the maximum number of targets per channel on the particular controller is MAX_TGT, the SCSI target IDs on a given channel should range from 0 to (MAX_TGT - 1). See the vendor documentation for more information.

• SCSI target IDs on one channel can be repeated on other channels.

  Example 1: The 5-channel models support a maximum of four targets per channel, that is, MAX_TGT = 4. Therefore, the SCSI target IDs on a given channel should range from 0 to 3.

  Example 2: The 3-channel models support a maximum of seven targets per channel, that is, MAX_TGT = 7. Therefore, the SCSI target IDs on a given channel should range from 0 to 6.

Known Problems and Limitations

• If a SCSI disk drive is not defined to be part of any physical pack within a system drive, it is automatically labeled as a standby drive. If any SCSI disk drive within a system drive fails, data on a standby drive may be lost due to the standby replacement procedure. This replacement procedure will overwrite the standby drive if the failed disk drive is configured with any level of redundancy (RAID levels 1, 5, and 6) and its size is identical to the size of the available standby drive.

  Therefore, even though a standby drive is physically connected, the system denies access to it so no data can be accidentally lost.

• Other than the standby rebuild of disk drives, which is described in the manufacturer's user's guide, these controllers do not support "hot-plugging" (adding or removing devices while the system is running).

  To add or remove devices, shut down the system, add or remove the devices, reconfigure the HBA using the vendor's configuration utility, and reconfigure-reboot (b -r) your system.

• The driver does not support variable-length tape drives or multivolume backup or restore for tape drives connected to the controller.

• Due to Mylex firmware limitations, SCSI devices such as tape and CD-ROM will not function reliably when attached on a channel with SCSI hard drives. Also, a tape block size greater than 32 Kbytes cannot be used. To be certain of correct SCSI device operation, use SCSI devices only on an otherwise unused channel, and with a fixed block size of 32 Kbytes or less.

• Long tape commands (erasing a large tape) may fail because the Mylex controllers have a one-hour timeout maximum for the command.

• Enable tag queuing only for SCSI disk drives that are officially tested and approved by Mylex Corporation for the DAC960 controller family and by IBM for the DMC960. Otherwise, disable tag queuing to avoid problems.

• (1212018) The command mt erase works but may report the following error message when it gets to the end of the tape:

  /dev/rmt/0 erase failed: I/O error

  This message can be ignored.