From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hans Reiser Subject: Re: journal size reiserfs vs reiser4 Date: Fri, 02 Sep 2005 00:19:55 -0700 Message-ID: <4317FD1B.504@namesys.com> References: <20050901134604.31ddd297@SiRiUS.home> <20050901144842.34629bcf@SiRiUS.home> <4316F9CC.2090904@namesys.com> <20050901150507.3d6f53c7@SiRiUS.home> <4316FD28.5020304@redhat.com> <43171D57.3030007@namesys.com> <431726F2.1090508@redhat.com> <4317F28F.80704@namesys.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: list-help: list-unsubscribe: list-post: Errors-To: flx@namesys.com In-Reply-To: <4317F28F.80704@namesys.com> List-Id: Content-Type: text/plain; charset="us-ascii" To: "Vladimir V. Saveliev" Cc: michael chang , Peter Staubach , reiserfs-list@namesys.com Vladimir V. Saveliev wrote: >Hello > >michael chang wrote: > > >>On 9/1/05, Peter Staubach wrote: >> >> >>>Hans Reiser wrote: >>> >>> >>> >>>>Research for filesystems generally says that as you get more than 85% >>>>full the performance goes down, by a lot as you get close to 100%. 5% >>>>is probably too little rather than too much. >>>> >>>> >>>> >>>Wow. What is all that space used for? >>> >>> > >Reiser4 allocates log records dynamically. So it has to allocate some disk space even when it is about to remove a file. >Reserved space is used when allocation is required to preform removal operation. >This allows to avoid returning ENOSPC on operations which are usually used to free disk space. > > It could probably be a lot less than 5%, 2% is more than enough I would guess, but we also need to reserve space to get good performance.