From mboxrd@z Thu Jan 1 00:00:00 1970 From: jim owens Subject: Re: Converting system to raid Date: Sat, 11 Apr 2009 13:40:30 -0400 Message-ID: <49E0D60E.7040904@hp.com> References: <003801c9b96d$21a0f420$0a00a8c0@vorg> <49DF0D06.8030705@musmo.com> <20090410195303.GB21242@cthulhu.home.robinhill.me.uk> <00cc01c9ba1d$3aefecf0$0a00a8c0@vorg> <20090410205942.GC21242@cthulhu.home.robinhill.me.uk> <00f301c9ba23$032025f0$0a00a8c0@vorg> <20090410215129.GD21242@cthulhu.home.robinhill.me.uk> <019701c9ba66$aeed5630$0a00a8c0@vorg> <20090411143642.GA9915@cthulhu.home.robinhill.me.uk> <49E0B188.8050009@hp.com> <49E0BAF9.3090209@garzik.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <49E0BAF9.3090209@garzik.org> Sender: linux-raid-owner@vger.kernel.org To: Jeff Garzik Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Jeff Garzik wrote: > jim owens wrote: >> nanosecond time stamps are a myth! > > Not true, in the age of NO_HZ... While nanosecond time is real on some hardware platforms, I don't know of any hard disk filesystem that does metadata updates at that level of granularity and guarantees distinct timestamps between writes at extremely short intervals. Even SSD performance would suck if we did that. The filesystem mod-time might have nanoseconds in it, but that does not mean 2 writes 100 nanoseconds apart will have different mod-times. jim