Hello Dave, Thursday, August 10, 2006, 12:29:05 AM, you wrote:
DF> Hi, DF> Note that these are page cache rates and that if the application DF> pushes harder and exposes the supporting device rates there is DF> another world of performance to be observed. This is where ZFS DF> gets to be a challenge as the relationship between the application DF> level I/O and the pool level is very hard to predict. For example DF> the COW may or may not have to read old data for a small I/O DF> update operation, and a large portion of the pool vdev capability DF> can be spent on this kind of overhead. Also, on read, if the DF> pattern is random, you may or may not receive any benefit from the DF> 32 KB to 128 KB reads on each disk of the pool vdev on behalf of a DF> small read, say 8 KB by the application, again lots of overhead DF> potential. I am not complaining, ZFS is great, I’m a fan, but you DF> definitely have your work cut out for you if you want to predict DF> its ability to scale for any given workload. I know, you have valid concerns. However in a tests I performed ZFS behaved better than UFS and it was most important for me. Does it mean that it will behave (performance) better than UFS in a production? Well, I don't know - but thanks to these tests (and some others I haven't posted) I'm more confident that it's likely it will not behave worse. And this is only performance point of view, there are others also important. ps. however I'm really concerned with ZFS behavior when a pool is almost full, there're lot of write transactions to that pool and server is restarted forcibly or panics. I observed that file systems on that pool will mount in 10-30 minutes each during zfs mount -a, and one CPU is completely consumed. It's during system start-up so basically whole system boots waits for it. It means additional 1 hour downtime. This is something really unexpected for me and unfortunately no one was really interested in my report - I know people are busy. But still if it hits other users when zfs pools will be already populated people won't be happy. For more details see my post here with subject: "zfs mount stuck in zil_replay". -- Best regards, Robert mailto:[EMAIL PROTECTED] http://milek.blogspot.com _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
