> From: Richard Elling [mailto:rich...@nexenta.com] > > With appropriate write caching and grouping or re-ordering of writes > algorithms, it should be possible to minimize the amount of file > interleaving and fragmentation on write that takes place. > > To some degree, ZFS already does this. The dynamic block sizing tries > to ensure > that a file is written into the largest block[1]
Yes, but the block sizes in question are typically up to 128K. As computed in my email 1 minute ago ... The "fragment" size needs to be on the order of 40 MB in order to effectively eliminate performance loss of fragmentation. > Also, ZFS has an intelligent prefetch algorithm that can hide some > performance > aspects of "defragmentation" on HDDs. Unfortunately, prefetch can only hide fragmentation on systems that have idle disk time. Prefetch isn't going to help you if you actually need to transfer a whole file as fast as possible. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
