Date: Wed, 27 Jan 2010 10:44:32 +0100 From: Gary Jennejohn <gary.jennejohn@freenet.de> To: Alexander Best <alexbestms@wwu.de> Cc: freebsd-hackers@FreeBSD.org Subject: Re: Spin down HDD after disk sync or before power off Message-ID: <20100127104432.5de75be7@ernst.jennejohn.org> In-Reply-To: <permail-20100126191723f7e55a9d00001a52-a_best01@message-id.uni-muenster.de> References: <permail-20100126191723f7e55a9d00001a52-a_best01@message-id.uni-muenster.de>
next in thread | previous in thread | raw e-mail | index | archive | help
On Tue, 26 Jan 2010 20:17:23 +0100 (CET) Alexander Best <alexbestms@wwu.de> wrote: > hi there, > > because of kern/140752 i looked through a discussion back in 2009 > (http://lists.freebsd.org/pipermail/freebsd-hackers/2009-March/027879.html) > concerning freebsd's hdd spin down procedure. right now ATA_FLUSHCACHE is > being used although the hitachi hdd specs referenced in the pr say that this > will not cause proper load/unload and thus an emergency unload will occur > which reduces the life expectancy of hdds dramatically (20.000 shutdowns vs. > 600.000 shutdowns). unfortunately the discussion back then didn't come up with > any sort of decision/patch. > > attached you'll find a very simple patch which issues ATA_STANDBY_IMMEDIATE > instead of ATA_FLUSHCACHE during hdd spin down. > > could somebody with hdd knowledge comment on this? this matter seems quite > important since there may be a chance that the current spin down mechanism in > freebsd damages hdds! > What if the disk doesn't support ATA_STANDBY_IMMEDIATE? Your patch then negates the benefit of calling ad_shutdown(), namely flushing the cache, if possible. I suggest putting your new code at the top and leaving the old code in an else-if clause. --- Gary Jennejohn
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20100127104432.5de75be7>