Date: Thu, 12 Mar 2009 12:30:15 +0100 From: Tijl Coosemans <tijl@ulyssis.org> To: freebsd-hackers@freebsd.org Cc: Tobias Blersch <abitos@abitos.org>, Oliver Fromme <olli@lurza.secnetix.de> Subject: Re: Spin down HDD after disk sync or before power off Message-ID: <200903121230.17041.tijl@ulyssis.org> In-Reply-To: <49B02211.1010809@abitos.org> References: <200903050758.n257wod8088426@lurza.secnetix.de> <49B02211.1010809@abitos.org>
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On Thursday 05 March 2009 20:03:45 Tobias Blersch wrote: > http://www.hitachigst.com/tech/techlib.nsf/techdocs/28DCCB17E0EEC5A086256= =464E006E2F5B >=20 > Thats the specification for my notebooks hard drive. Section 6.6 > Reliability gives data about how to power-off the disk. It also > contains numbers of supported load/unloads and emergency unloads. > Emergency unloads are invoked when the heads are still loaded and > power fails. Quoting that document: 10.4.1 Emergency unload (...) Emergency unload is intended to be invoked in rare situations. Because this operation is inherently uncontrolled, it is more mechanically stressful than a normal unload. A single emergency unload operation is more stressful than 100 normal unloads. Use of emergency unload reduces the start/stop life of the HDD at a rate at least 100X faster than that of normal unload, and may damage the HDD. 10.4.2 Required power-off sequence (...) You may then turn off the HDD in the following order: =E2=80=A2 Issue Standby Immediate or sleep command. =E2=80=A2 Wait until COMMAND COMPLETE STATUS is returned. (It may take up= to 350ms in typical case). =E2=80=A2 Terminate power to HDD. This power-down sequence should be followed for entry into any system power-down state, or system suspend state, or system hibernation state. In a robustly designed system, emergency unload is limited to rare scenarios such as battery removal during operation.
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