Date: Thu, 5 Mar 2009 11:49:10 -0800 (PST) From: Nate Eldredge <neldredge@math.ucsd.edu> To: Tobias Blersch <abitos@abitos.org> Cc: freebsd-hackers@freebsd.org Subject: Re: Spin down HDD after disk sync or before power off Message-ID: <Pine.GSO.4.64.0903051131530.24456@zeno.ucsd.edu> In-Reply-To: <49B02211.1010809@abitos.org> References: <200903050758.n257wod8088426@lurza.secnetix.de> <49B02211.1010809@abitos.org>
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On Thu, 5 Mar 2009, Tobias Blersch wrote: > Oliver Fromme wrote: >> > Joerg Sonnenberger wrote: >> > This is not true. Many hard disks don't like having to do an emergency >> > shutdown as it affects the disk life time negatively. That's what >> > happens if you poweroff the machine when the disks are still spinning. >> >> Can you point to any authoritative information (URL) about >> that claim, such as vendor specs, white paper or similar? > > http://www.hitachigst.com/tech/techlib.nsf/techdocs/28DCCB17E0EEC5A086256F4E006E2F5B > > 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. Ok, I didn't know that. There are some drives that can unload the heads normally on power loss and don't need any special handling, and I was under the mistaken impression that this was universal. But the documentation suggests that this should be a BIOS function. When the kernel tries to poweroff the system, isn't that normally done via the BIOS (perhaps with ACPI/APM)? So maybe the BIOS is supposed to unload the heads (by sending a standby/sleep command) before cutting the power. This makes sense in some ways. Suppose the drive is attached to a weird ATA controller that FreeBSD doesn't know anything about. (Maybe it's used by the other system in a dual-boot setup.) There's no way that FreeBSD could send it a power-down sequence, but the BIOS could. Perhaps the OP's BIOS for some reason doesn't do this correctly. -- Nate Eldredge neldredge@math.ucsd.edu
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