Robert Milkowski wrote On 06/25/06 04:12,:
Hello Neil, Saturday, June 24, 2006, 3:46:34 PM, you wrote: NP> Chris, NP> The data will be written twice on ZFS using NFS. This is because NFS NP> on closing the file internally uses fsync to cause the writes to be NP> committed. This causes the ZIL to immediately write the data to the intent log. NP> Later the data is also written committed as part of the pools transaction group NP> commit, at which point the intent block blocks are freed. NP> It does seem inefficient to doubly write the data. In fact for blocks NP> larger than zfs_immediate_write_sz (was 64K but now 32K after 6440499 fixed) NP> we write the data block and also an intent log record with the block pointer. NP> During txg commit we link this block into the pool tree. By experimentation NP> we found 32K to be the (current) cutoff point. As the nfsd at most write 32K NP> they do not benefit from this. Is 32KB easily tuned (mdb?)?
I'm not sure. NFS folk?
I guess not but perhaps. And why only for blocks larger than zfs_immediate_write_sz?
When data is large enough (currently >32K) it's more efficient to directly write the block, and additionally save the block pointer in a ZIL record. Otherwise it's more efficient to copy the data into a large log block potentially along with other writes. -- Neil _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
