From mboxrd@z Thu Jan 1 00:00:00 1970 From: Justin Piszcz Subject: Re: Distributed spares Date: Mon, 13 Oct 2008 18:11:48 -0400 (EDT) Message-ID: References: <48F3C2A1.3080607@tmr.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Return-path: In-Reply-To: <48F3C2A1.3080607@tmr.com> Sender: linux-raid-owner@vger.kernel.org To: Bill Davidsen Cc: Neil Brown , Linux RAID List-Id: linux-raid.ids On Mon, 13 Oct 2008, Bill Davidsen wrote: > Over a year ago I mentioned RAID-5e, a RAID-5 with the spare(s) distributed > over multiple drives. This has come up again, so I thought I'd just mention > why, and what advantages it offers. > > By spreading the spare over multiple drives the head motion of normal access > is spread over one (or several) more drives. This reduces seeks, improves > performance, etc. The benefit reduces as the number of drives in the array > gets larger, obviously with four drives using only three for normal operation > is slower than four, etc. And by using all the drives all the time, the > chance of a spare being undetected after going bad is reduced. > > This becomes important as array drive counts shrink. Lower cost for drives > ($100/TB!), and attempts to drop power use by using fewer drives, result in > an overall drop in drive count, important in serious applications. > > All that said, I would really like to bring this up one more time, even if > the answer is "no interest." > > -- > Bill Davidsen > "Woe unto the statesman who makes war without a reason that will still > be valid when the war is over..." Otto von Bismark > > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Bill, Not a bad idea; however, can the same not be acheived (somewhat) by performing daily/smart, weekly/long tests on the drive to validate its health? I find this to work fairly well on a large scale. Justin.