Here's the relevant output of dmesg after a boot which failed to set the dma flag on /dev/hda. All other settings on hda and all settings on hdb were applied correctly.
[17179608.932000] hda: dma_timer_expiry: dma status == 0x60 [17179608.932000] hda: DMA timeout retry [17179608.932000] hda: timeout waiting for DMA [17179608.932000] hdb: status error: status=0x58 { DriveReady SeekComplete DataRequest } [17179608.932000] ide: failed opcode was: 0xe7 [17179608.932000] hdb: drive not ready for command [17179609.132000] hdb: status error: status=0x58 { DriveReady SeekComplete DataRequest } [17179609.132000] ide: failed opcode was: unknown [17179609.132000] hdb: drive not ready for command [17179609.140000] hdb: status error: status=0x7f { DriveReady DeviceFault SeekComplete DataRequest CorrectedError Index Error } [17179609.140000] hdb: status error: error=0x7f { DriveStatusError UncorrectableError SectorIdNotFound TrackZeroNotFound AddrMarkNotFound }, LBAsect=260013951, sector=0 [17179609.140000] ide: failed opcode was: 0xe7 [17179609.140000] hdb: drive not ready for command [17179609.140000] hdb: wcache flush failed! [17179609.148000] hdb: status error: status=0x7f { DriveReady DeviceFault SeekComplete DataRequest CorrectedError Index Error } [17179609.148000] hdb: status error: error=0x7f { DriveStatusError UncorrectableError SectorIdNotFound TrackZeroNotFound AddrMarkNotFound }, LBAsect=260013951, sector=0 [17179609.148000] ide: failed opcode was: unknown [17179609.148000] hdb: drive not ready for command [17179609.168000] hda: dma_intr: status=0x58 { DriveReady SeekComplete DataRequest } [17179609.168000] ide: failed opcode was: unknown [17179614.176000] hda: status timeout: status=0xd0 { Busy } [17179614.176000] ide: failed opcode was: unknown [17179614.176000] hda: DMA disabled [17179614.176000] hdb: DMA disabled [17179614.176000] hda: drive not ready for command [17179614.176000] hdb: set_drive_speed_status: status=0x58 { DriveReady SeekComplete DataRequest } [17179614.176000] ide: failed opcode was: unknown [17179614.224000] ide0: reset: success For rerefence, here are my /etc/hdparm.conf settings: /dev/cdrom { dma = on } /dev/hda { mult_sect_io = 16 io32_support = 3 dma = on } /dev/hdb { mult_sect_io = 16 io32_support = 3 dma = on } -- hdparm apparently not run during boot https://launchpad.net/bugs/46414 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs