Robert Milkowski wrote On 06/27/06 03:00,:
Hello Chris,
Tuesday, June 27, 2006, 1:07:31 AM, you wrote:
CC> On 6/26/06, Neil Perrin <[EMAIL PROTECTED]> wrote:
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?
CC> I think he is referring to the zfs_immediate_write_sz variable, but
Exactly, I was asking about this not NFS.
Sorry for the confusion. The zfs_immediate_write_sz varaible was meant for
internal use and not really intended for public tuning. However, yes it could
be tuned dynamically anytime using mdb, or set in /etc/system
--
Neil
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