From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Staubach Subject: Re: journal size reiserfs vs reiser4 Date: Thu, 01 Sep 2005 13:36:32 -0400 Message-ID: <43173C20.7070107@redhat.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> <43173463.40302@slaphack.com> <43173A11.2000801@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: <43173A11.2000801@namesys.com> List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Hans Reiser Cc: David Masover , vs@namesys.com, reiserfs-list@namesys.com Hans Reiser wrote: >>>> >>>> >>>Wow. What is all that space used for? Other journalling file >>>systems that >>>I have seen have limited things like journals to a much smaller space, >>> >>> >BSD FFS has a 10% limit unless you are root. They are correct to do so. > Yes, they reserve that space so that their algorithms to choose blocks from the various cylinder groups can continue to choose blocks in decent locations. BSD FFS doesn't journal though. The SunOS UFS does journal metadata and retains the same 10% limit. It was discovered that the journal didn't need to be very big in order to maximize performance though. A very small log would do as well as a very large log. It would be interesting to pick a benchmark which represents some market that usually deploys reiersfs and then experiment with various aspects of the file system, including the reserve space. It is easy to do, mostly just time consuming and requires a fair amount of resources. ps