Kernel panics when writing/reading SCSI devices; potential solution; Adaptec cards don't work with Retrospect

There has been a resurgence of user reports indicating kernel panics when writing to or reading from SCSI devices under Mac OS X 10.4.x.

MacFixIt reader Dave writes:

"I use EMC's (used to be Dantz) Retrospect Backup Program which has been around for some time. The version used in the test was the latest, 6.126 I believe. Basically, I load up retrospect, and I try to start a backup to the SCSI Tape Drive (connected to an Adaptec SCSI card) and every time it Kernel Panics. I can however erase the tapes and that sort of thing.

"My diagnoses of the panic logs determine its a kext issue with the Adaptec78XX Kernel Extension, which at version 1.1.2 has been around for a while. I have also been able to determine that since I can erase tapes, and get information on them, as well as access SCSI Hard Drives, that this isn't an issue with the SCSI Card itself or a conflict between the ATA/66 Card and the SCSI Card.

"To Rule out it being the G3, I put the Tape Drive on my Quicksilver G4 and got an identical panic."

We covered some issues with SCSI devices in our Mac OS X 10.4.0 special report, and identified a workaround, successful for many users, which involves removing the following files from the /System/Library/Extensions folder:

• Adaptec 290X-2930.kext
• Adaptec 29160x.kext
• Adaptec 39160x.kext

but leaving the file

• Adaptec 78XXSCSI.kext

in place, then restarting.

UPDATE: It appears that Adapetc's SCSI cards are not compatible with Retrospect under Mac OS X, and are the cause for some cases of the aforementioned kernel panics.

Robin from EMC Dantz Technical Support technical support writes:

"EMC Dantz has tested Adaptec cards and they are not supported on Mac OS X with Retrospect."

MacFixIt reader Keith adds:

"Our experience, both on our bench and in the field w/clients, has been that the Adaptec SCSI adapters do not support Retrospect (or vice versa?), and this support has been lacking since OS 10.3. I realize that they've released updated drivers which were supposed to have remedied this problem but we've had no luck with the Dantz/EMC fixes. Likewise we?ve had problems using fixed media Ultra160 and Ultra320 hard drives w/Adaptec SCSI adapters.

"Our solution has been to exclusively use ATTO SCSI adapters. The driver is fully supported and by merely 'tuning' the target/bus/host configuration with the ATTO software and some slight changes to OpenFirmware via the line-command interface accessible at boot our SCSI experience has been close to perfect, regardless of the type of device (fixed media, tape, etc.)."

If your Mac is experiencing kernel panics when interacting with SCSI devices, please drop us a line at late-breakers@macfixit.com.

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