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From Ashwin Jayaprakash <ashwin.jayaprak...@gmail.com>
Subject Recovery log on /dev/shm?
Date Thu, 01 Sep 2011 20:31:11 GMT
This is a follow up to a question I posted in July 2010 - about whether the
recovery log could be redirected to /dev/null or some such low latency drive
[http://markmail.org/thread/3edpfmvn2fhyg5wv].

I just found out that Linux distros with 2.6 kernel have a built-in shared
memory file system that runs purely in memory - /dev/shm. Since this
provides recovery across JVM restarts (but not OS restarts) wouldn't this be
sufficient to run the ZK nodes off this drive? Replicas are on other
machines anyway so FT/HA is already there. It's just that disk latency can
be eliminated completely.

[Apologies if you guys are already aware of /dev/shm]

I ran some simple Java IO tests (not full ZK) on this drive and I wanted to
share my results. Might be of some use to apps that require low latency:
http://javaforu.blogspot.com/2011/09/ram-disk-is-already-in-linux-and-nobody.html

Ashwin.

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