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Marc Perkel wrote: > Trying to save power consumption. I have a backup drive that is used > only once a day to back up the main drive. So - why should I run it more > that 10 minutes a day? What I'd like to do is keep it in an off state > and then at night power it on, mount it up, do the backup, unmount it, > and shut it down. Can I do that? Yes, from lk 2.6.14 onwards. An implementation (based on SAT: http://www.t10.org/ftp/t10/drafts/sat/sat-r07.pdf) of the START STOP UNIT SCSI command went into libata in lk 2.6.14 . Hence you can use SCSI tools such as sg_start (sg3_utils) or sdparm (sdparm) to place a SATA disk in standby mode. For example: "sg_start 0 /dev/sda" and "sdparm --command=stop /dev/sda" are equivalent to "hdparm -y". The next command sent to that disk will cause it to spin up again. The power state machines of SCSI disks, ATA disks and CD/DVD drives overlap but are not the same. SATA and SAS transports add some wrinkles, see: http://www.torque.net/sg/power.html Spinning down disks with no mounted file systems makes sense. However repeatedly spinning down a disk that is periodically (e.g. 30 seconds later) accessed may shorten its life. In lk 2.6.15-rc1 implementations of the ATA COMMAND PASS THROUGH (12 and 16 byte) SCSI commands went into libata. These are defined in SAT (reference above). libata also translates the HDIO_DRIVE_CMD and HDIO_DRIVE_TASK ioctls into those pass through commands. Recent versions of hdparm (I've tried 6.1 and 6.3) work as expected. Hence "hdparm -y /dev/sda" puts the libata-connected SATA disk /dev/sda into standby mode. smartmontools also works for libata-connected SATA disks in lk 2.6.15-rc1 . The picture is not as bright for external USB and 1394 enclosures of ATA disks. They need to either support the START STOP UNIT SCSI command or the SAT pass through commands. I have not seen the former and won't hold my breath waiting for the latter. Doug Gilbert - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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