From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tom Vier Subject: Re: Plugin for corruption resistance? Date: Fri, 11 Feb 2005 15:53:50 -0500 Message-ID: <20050211205350.GA13345@zero> References: Reply-To: Tom Vier Mime-Version: 1.0 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 On Fri, Feb 11, 2005 at 01:58:59PM -0500, Gregory Maxwell wrote: > 1. Lots of applications today (such a P2P sharing systems) need the > hashes of files.. it's inefficient to keep recomputing them. The file > system always knows when a file changes, so it can be setup to always > return the correct hash. That should be done in userland, imho. Especially since different apps use lots of different hashes. I was thinking about this kind of stuff (ECC plugin for r4) not too long ago. Hashing the whole file is too slow; if you update a single block, the whole file has to be read in to recalculate. Adding, say, one sector of crc for each block would be a lot more feasible. I think the best way to do this though, would be to write a virtual blk driver that works like loop back (ie, uses a backing file/dev), and shortens the overall size by one sector * number of blocks. Actually, you could probably copy the raid5 md code and rewrite it to only use one device. I'd try that first. -- Tom Vier DSA Key ID 0x15741ECE