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
[email protected]
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