On Wed, 2007-01-24 at 11:07 +0900, Tejun Heo wrote: > Henrique de Moraes Holschuh wrote: > > On Tue, 23 Jan 2007, Tejun Heo wrote: > >> Henrique de Moraes Holschuh wrote: > >>> Does SATA electrical conector keying let the disk firmware unload > >>> heads before the user manages to pull it out enough to sever power? > >> I don't think so. [...] > Agreed.
OK, so here comes the next revision, I hope it can be put in the docs/on the web page now: SATA Hotplug from the User Side In general, before unplugging a drive you must stop using it. This means unmounting all partitions, removing the disk from a potential raid array / device mapper / crypt setup. Also depending on your disk-bay it might be a good idea to power down the drive using hdparm -Y followed by a scsiadd -r. BIG FAT WARNING: if your SATA bay does not do electrical connector keying to let the disk firmware unload heads before the user manages to pull it out the drive will do an emergency head unload, which is not good and will likely reduce the drive's lifetime. • For SIL3114 and SIL3124, AHCI and the CK804 flavour of sata_nv you - in principle - don't have to run any commands at all. It should notice when you yank the cable, or plug in a new device. All you have to do is to stop using the devices before unplugging, e.g. unmount partitions on the disk or remove the disk from a dm setup). However it is recommended to power down the drive using hdparm -Y followed by a scsiadd -r as stated above. One can validate which disks are attached using ``scsiadd -p''. In the following example the disk on scsi host 3 channel 0 id 0 lun 0 will be removed: # scsiadd -p Attached devices: Host: scsi2 Channel: 00 Id: 00 Lun: 00 Vendor: ATA Model: ST3400832AS Rev: 3.01 Type: Direct-Access ANSI SCSI revision: 05 Host: scsi3 Channel: 00 Id: 00 Lun: 00 Vendor: ATA Model: ST3400620AS Rev: 3.AA Type: Direct-Access ANSI SCSI revision: 05 # scsiadd -r 3 0 0 0 Note that the device name may change from e.g. /dev/sdd to /dev/sde on a remove/reinsert cycle (this can be fixed by using udev-provided persistent names). Also note that it is perfectly normal to see messages like this in dmesg: <removing /dev/sdd> ata4: exception Emask 0x10 SAct 0x0 SErr 0x10000 action 0x2 frozen ata4: hard resetting port ata4: SATA link down (SStatus 0 SControl 310) ata4: failed to recover some devices, retrying in 5 secs ata4: hard resetting port ata4: SATA link down (SStatus 0 SControl 310) ata4: failed to recover some devices, retrying in 5 secs ata4: hard resetting port ata4: SATA link down (SStatus 0 SControl 310) ata4.00: disabled ata4: EH complete ata4.00: detaching (SCSI 3:0:0:0) Synchronizing SCSI cache for disk sdd: FAILED status = 0, message = 00, host = 4, driver = 00 <3>ata4: exception Emask 0x10 SAct 0x0 SErr 0x50000 action 0x2 frozen ata4: hard resetting port ata4: COMRESET failed (device not ready) ata4: hardreset failed, retrying in 5 secs ata4: hard resetting port ata4: COMRESET failed (device not ready) ata4: hardreset failed, retrying in 5 secs ata4: hard resetting port <reinserting the disk> ata4: SATA link up 1.5 Gbps (SStatus 113 SControl 310) ata4.00: ATA-7, max UDMA/133, 1465149168 sectors: LBA48 NCQ (depth 0/32) ata4.00: configured for UDMA/100 ata4: EH complete scsi 3:0:0:0: Direct-Access ATA ST3750640AS 3.AA PQ: 0 ANSI: 5 SCSI device sde: 1465149168 512-byte hdwr sectors (750156 MB) sde: Write Protect is off sde: Mode Sense: 00 3a 00 00 SCSI device sde: drive cache: write back SCSI device sde: 1465149168 512-byte hdwr sectors (750156 MB) sde: Write Protect is off sde: Mode Sense: 00 3a 00 00 SCSI device sde: drive cache: write back sde: unknown partition table sd 3:0:0:0: Attached scsi disk sde sd 3:0:0:0: Attached scsi generic sg3 type 0 However if you happen to see messages like scsi 3:0:0:0: rejecting I/O to dead device scsi 4:0:0:0: rejecting I/O to dead device scsi 5:0:0:0: rejecting I/O to dead device you did not stop using the devices before unplugging (check that you unmounted all partitions, removed the disk from a raid array, dmsetup, cryptsetup). If you have no pending IO to the device, there won't be 'rejects IO to dead device' messages. • For other chipsets one in addition might have to run scsiadd -s on reinserting the disk. • Note that it might not be such a good idea to do the above on drivers which don't implement the new EH yet. Those are as of January 2007: sata_nv, sata_promise (getting there) and sata_sx4. Soeren (beeing stuck in a train which again seems to be stuck in a lot of snow somewhere in southern germany...) -- For the one fact about the future of which we can be certain is that it will be utterly fantastic. -- Arthur C. Clarke, 1962 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
