-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Ed Schouten wrote: | * Daniel Thiele <dthi...@gmx.net> wrote: |> Looking at the numbers in the Hitachi drive specifications Tobias an I |> dug out from the Hitachi website (see replies in the Joerg Sonnenberger |> branch of this thread) the normal Load/Unload count is about 30 times |> higher than the Emergency Unload count. <snip> | | Have you also looked at the definition of `emergency unload'? Maybe this | number doesn't actually refer to the number of unloads caused by power | loss, but because they detect a very high amount of vibration. But I'm | not a hard disk expert. |
I am no disk expert either. The Hitachi TravelStar 5K320 specification says on this topic: 6.3.6.1 Emergency unload When hard disk drive power is interrupted while the heads are still loaded the micro code cannot operate and the normal 5 -volt power is unavailable to unload the heads. In this case, normal unload is not possible. The heads are unloaded by routing the back EMF of the spinning motor to the voice coil. The actuator velocity is greater than the normal case and the unload process is inherently less controllable without a normal seek current profile. 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. So it seems to be a kind of self protection mechanism that electro-mechanically tries to get the heads in a save position without firmware or microcode intervention in the case of a sudden power outage. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.11 (FreeBSD) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAkmwSAIACgkQCOZKcWNoXg7vlQCgzcSvK25cLBfemmsC7/xXmtcl /7kAmwQGM5xFVjZJW7YGqNWaWIXuXqcu =cPcz -----END PGP SIGNATURE----- _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
