From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 5 Mar 2008 05:00:20 +0100 From: Enrico Weigelt To: Fans of the OS Plan 9 from Bell Labs <9fans@cse.psu.edu> Message-ID: <20080305040019.GA13663@nibiru.local> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.1i Subject: [9fans] thoughs about venti+fossil Topicbox-Message-UUID: 6ef24ab4-ead3-11e9-9d60-3106f5b1d025 Hi folks, some thoughts about venti that go around in my mind: 1. how stable is the keying ? sha-1 has only 160 bits, while data blocks may be up to 56k long. so, the mapping is only unique into one direction (not one-to-one). how can we be *really sure*, that - even on very large storages (TB or even PB) - data to each key is alway (one-to-one) unique ? 2. what approx. compression level could be assumed on large storages by putting together equal data blocks (on several kind of data, eg. typical office documents vs. media) ? 3. what happens on the space consumtion if venti is used as storage for heavily rw filesystems for a longer time (not as permanent archive) - how much space will be wasted ? should we add some method for block expiry (eg. timeouts of reference counters) ? 4. assuming #1 can be answered 100% yes - would it suit for an very large (several PB) heavily distributed storage (eg. for some kind of distributed, redundant filesystem) ? cu -- --------------------------------------------------------------------- Enrico Weigelt == metux IT service - http://www.metux.de/ --------------------------------------------------------------------- Please visit the OpenSource QM Taskforce: http://wiki.metux.de/public/OpenSource_QM_Taskforce Patches / Fixes for a lot dozens of packages in dozens of versions: http://patches.metux.de/ ---------------------------------------------------------------------