Subject: [nfsv4] New pNFS block draft & issues

From: [email-masked]
Date: Tue, 3 Jan 2006 18:35:53 -0500

The new version of the pNFS block/volume layout draft has
been submitted to the secretariat - it should appear soon.

There are a couple of issues this draft raises with the
base pNFS operations:
- Need to have another look at not using a "reclaim bit"
	for allocated but uncommitted layout portions.
	At least for block/volume clients, this limits
	uncommitted data to the cache size.
- EOF change issues.  The CB_SIZECHANGED callback doesn't
	appear to be useful, because there's no good way
	to sort out who wins when there's a concurrent
	conflicting commit.  In addition, the block/volume
	layout has layout-specific issues around who zeroes
	a partial block created by an EOF move.
I should have caught the EOF issues earlier, as HighRoad
has scars from figuring out how to get them right.
In its current form, I think pNFS has to make all EOF
changes at the server, recalling conflicting layout
portions as necessary to get the right effects to happen.

There's more discussion of these in the draft, which should
appear shortly (with a draft-ietf-nfsv4-* name).

Thanks,
--David
----------------------------------------------------
David L. Black, Senior Technologist
EMC Corporation, 176 South St., Hopkinton, MA  01748
+1 (508) 293-7953             FAX: +1 (508) 293-7786
[email-masked]        Mobile: +1 (978) 394-7754
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