On 24/02/2010 02:21, v wrote:
Hi, Thanks for the reply. So the problem of sequential read after random write problem exist in zfs. I wonder if it is a real problem, ie, for example cause longer backup time, will it be addressed in future?
Once the famous bp rewriter is integrated and a defrag functionality built on top of it you will be able to re-arrange your data again so it is sequential again.
So I should ask anther question: is zfs suitable for an environment that has lots of data changes? I think for random I/O, there will be no such performance penalty, but if you backup a zfs dataset, must the backup utility sequentially read blocks of a dataset? Will zfs dataset suitable for database temporary tablespace or online redo logs? Will a defrag utility be implemented?
From my own experience it is not an issue in most cases - environments with lots of random writes tend to do random reads as well anyway. Then when it comes to backup - yes, it might get slower over time but in most cases it will still be faster than your network bandwidth so it would not be a bottleneck. Additionally if your environment is doing lots of random updates ZFS (or a CoW fs in general) should be able to perform them much faster than other filesystems.
But of course YMMV. -- Robert Milkowski http://milek.blogspot.com _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
