On Sep 7, 2009, at 3:49 AM, Sriram Narayanan wrote:
Folks:
I gave a presentation last weekend on how one could use Zones, ZFS and
Crossbow to recreate deployments scenarios on one's computer (to the
extent possible).
I've received the following question, and would like to ask the ZFS
Community for answers.
-- Sriram
---------- Forwarded message ----------
From: Ritesh Raj Sarraf <r...@researchut.com>
Date: Mon, Sep 7, 2009 at 2:20 PM
Subject: [ilugb] Does ZFS support Hole Punching/Discard
To: ilug-bengal...@googlegroups.com
Thanks to Sriram for the nice walk through on "Beyond localhost".
There was one item I forgot to ask. Does ZFS support Hole Punching ?
I only know of "hole punching" in the context of networking. ZFS doesn't
do networking, so the pedantic answer is no.
After pushing off to BP is when I remembered of this issue. Here's a
link about
this issue and its state in Linux.
http://lwn.net/Articles/293658/
This is an article about the new TRIM command. It would be important for
file systems which write their metadata to the same physical location
or use
a MRU replacement algorithm. But ZFS is copy-on-write, so the metadata
is
allocated from free space and ZFS is transactional, not directly MRU.
It is not
expected that this problem would affect ZFS file systems for an extended
period of time, which you can further extend by using snapshots.
Interesting sidebar: you can measure how many times a block is
rewritten in
a Solaris system, but the data collection and analysis is a rather
large task.
I don't know of anyone patient enough to do it long enough to get near
the
endurance of an SSD.
-- richard
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