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When running Linux on a server or NAS device, you might want to hot-swap disks without bringing the system down. For machines without a RAID controller, this might be a little bit tricker since you have to tell Linux to remove and add the device manually. This page will go over how to hot-swap SATA devices in Linux.

==Removing a Drive==
If a device becomes unresponsive or if you simply just want to remove a SATA disk from a running system:

#Ensure the disk is unmounted.
#Ensure the disk isn't used by swap or LVM groups.
#Remove the disk from the system by running {{code|echo 1 > /sys/block/sdX/device/delete}}. This should also power off the drive. If this doesn't work, try using [[hdparm]] to take the deivce to the lowest power setting with <code>hdparm -Y /dev/sdx</code> and then try again.

Once the drive spins down, you can disconnect the power and SATA connector. 

==Rescanning SATA Bus==
Depending on the chipset and SATA controller, when you connect a drive to the system, you may need to force a rescan of the bus before the drive shows up on the system. On Linux, you will need to trigger a rescan.

Determine the controller the disk is attached to and trigger a rescan. Listing the scsi_host directory should give you a clue on what host is associated with which device:
{{highlight|lang=terminal|code=
# ls -al /sys/class/scsi_host
lrwxrwxrwx  1 root root 0 Feb 18 22:21 host0 -> ../../devices/pci0000:00/0000:00:06.0/ata1/host0/scsi_host/host0/
lrwxrwxrwx  1 root root 0 Feb 18 22:21 host1 -> ../../devices/pci0000:00/0000:00:06.0/ata2/host1/scsi_host/host1/
lrwxrwxrwx  1 root root 0 Feb 18 22:21 host2 -> ../../devices/pci0000:00/0000:00:04.0/0000:01:06.0/ata3/host2/scsi_host/host2/
}}Trigger a rescan by writing 3 dashes (which denotes wildcards) to the scan command. Each of the 3 fields represents the channel, SCSI target ID, and LUN, respectively.
{{highlight|lang=terminal|code=
# echo "- - -" > /sys/class/scsi_host/host#/scan
}}

If you're not sure which controller your disk is connected to, you may try to rescan all controllers:{{highlight
| lang = terminal
| code = # for arg in /sys/class/scsi_host/*/scan; do echo "- - -" > $arg; done
}}

Once the rescan is triggered, run <code>dmesg</code> to see if a new disk was attached to the system.


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