admin-guide/laptops/disk-shock-protection.rst

7 Last modified: 2008-10-03
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21 ATA/ATAPI-7 specifies the IDLE IMMEDIATE command with unload feature.
22 Issuing this command should cause the drive to switch to idle mode and
25 a shock protection facility. The idea is to stop all I/O operations on
26 the internal hard drive and park its heads on the ramp when critical
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42 -EOPNOTSUPP if the device does not support the unload feature.
44 of the respective drive off the platter and block all I/O operations
49 -EOVERFLOW, but heads will be parked anyway and the timeout will be
55 immediately by specifying a timeout of 0. Values below -2 are rejected
56 with -EINVAL (see below for the special meaning of -1 and -2). If the
62 For example, do the following in order to park the heads of drive
63 /dev/sda and stop all I/O operations for five seconds::
77 unload operation to complete is vendor specific. The hint in ATA-7
79 been dropped in ATA-8.
83 been issued to a device successfully, all I/O operations on the
92 which means that a user-issued head parking request to one device may
93 actually result in stopping I/O to a whole bunch of devices. However,
97 the same port as the hard drive, it generally *should* recover just
98 fine from the occasional buffer under-run incurred by a head park
100 than its libata counterpart (i.e. your disk is called /dev/hda
101 instead of /dev/sda), then parking the heads of one drive (drive X)
102 will generally not affect the mode of operation of another drive
103 (drive Y) on the same port as described above. It is only when a port
104 reset is required to recover from an exception on drive Y that further
105 I/O operations on that drive (and the reset itself) will be delayed
106 until drive X is no longer in the parked state.
109 version of the ATA standard than ATA-7, but do support the unload
114 laptop or the hard drive itself told you so), then you can tell the
115 kernel to enable the usage of this feature for that drive by writing
116 the special value -1 to the unload_heads attribute::
118 	# echo -1 > /sys/block/sda/device/unload_heads
120 will enable the feature for /dev/sda, and giving -2 instead of -1 will
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133 protection on different systems. Unfortunately, I only know of a
138 - https://www.thinkwiki.org/wiki/HDAPS
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