From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sander Subject: Re: Fwd: My Dad suggests a redundant copies plugin Date: Thu, 27 Oct 2005 09:10:53 +0200 Message-ID: <20051027071052.GA17692@favonius> References: <435DC714.6000505@namesys.com> <20051025072537.GB8402@favonius> Reply-To: sander@humilis.net Mime-Version: 1.0 Return-path: list-help: list-unsubscribe: list-post: Errors-To: flx@namesys.com Content-Disposition: inline In-Reply-To: List-Id: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Gregory Maxwell Cc: reiserfs-list@namesys.com Gregory Maxwell wrote (ao): > On 10/25/05, Sander wrote: > > That will kill performance badly. First of all the two read/writes > > needed, and second because you have to seek from one end to the disk > > to the other every time you read/write something. > > Kill it worse for writes than a filesytem without wandering logs? I > don't think so, since they double write in any case... Since reiser4 > defers flushes you don't end up seeking all over the disk, you will > write out a nice long queue, then a little seeking to ripple up the > transaction(s). > > Reading will not be harmed since we will expect the underlying disk to > report read failures. Either way, more reads and writes are need with such a plugin, or am I missing something? > > And what is the advantage? You are not protected against a lot of > > disk failures (only against bad blocks, right?). > > Badblocks have become the most common non-transient failure mode of > disks by far. That is not my experience. Where does this knowledge come from? > > There is a lot more advantage in buying two disks and do raid over > > them. This is (much) cheaper, gives better performance and gives > > more protection. > > Cheaper how? Two disks are cheaper than one? If you opt for a copy of everything, yes. Because of a 500GB drive only half of it is effectively usable. Two 250GB disks raid1 are much cheaper than one 500GB disk. -- Humilis IT Services and Solutions http://www.humilis.net