On Sat, 7 Jun 2008, Mattias Pantzare wrote: > > If I need to count useage I can use du. But if you can implement space > usage info on a per-uid basis you are not far from quota per uid...
That sounds like quite a challenge. UIDs are just numbers and new ones can appear at any time. Files with existing UIDs can have their UIDs switched from one to another at any time. The space used per UID needs to be tallied continuously and needs to track every change, including real-time file growth and truncation. We are ultimately talking about 128 bit counters here. Instead of having one counter per filesystem we now have potentially hundreds of thousands, which represents substantial memory. Multicore systems have the additional challenge that this complex information needs to be effectively shared between cores. Imagine if you have 512 CPU cores, all of which are running some of the ZFS code and have their own caches which become invalidated whenever one of those counters is updated. This sounds like a no-go for an almost infinite-sized pooled "last word" filesystem like ZFS. ZFS is already quite lazy at evaluating space consumption. With ZFS, 'du' does not always reflect true usage since updates are delayed. Bob ====================================== Bob Friesenhahn [EMAIL PROTECTED], http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
