I just realized that this was on the pvfs-developers rather than
pvfs2-developers list. Moving it over.
-Phil
-------- Original Message --------
Subject: Re: [Pvfs-developers] About cache at server side!
Date: Tue, 23 Mar 2010 10:17:04 -0500
From: Phil Carns <[email protected]>
To: bin dong <[email protected]>
CC: [email protected]
References: <[email protected]>
Hi,
There are two issues here; caching on the client side and caching on the
server side.
The PVFS client never caches data. In that sense, the client acts as if
O_DIRECT is the default, except that there are no restrictions on alignment.
The PVFS server, however, is free to use the buffer cache, which I think
is the main issue that you are asking about. There is no mount option
to control this, but you can change the server configuration. The
TroveMethod parameter in the server configuration file controls what
mechanism the server uses for I/O on the backend. The directio method
causes it to use O_DIRECT for all I/O:
http://www.pvfs.org/cvs/pvfs-2-8-branch-docs/doc//pvfs-config-options.php#TroveMethod
It defaults to the altio method, which uses threads along with normal
(cached) I/O operations.
-Phil
bin dong wrote:
hi all,
I need to do one raw performance test of PVFS2 with IOR, whereas
i don't know
how to bypass the cache at server side.
I know, there is one option O_DIRECT for traditional file system
to bypass the buffer,
and IOR also offer this option when using POSIX interface. So , I
wonder when I pass
the O_DIRECT option to IOR which uses POSIX interface, whether
the PVFS2 server
would follow this order to bypass the server's file
system's cache at server side or not?
In other words, when mounting PVFS2 at client side(/mnt/pvfs2/),
and open some file
like "/mnt/pvfs2/test" with O_DIRECT option, does the server
would bypass the cache
of the server's local file system when I do read/write afterwards?
your help would be appreciated.
---------------------------
Bin Dong
Beihang University
------------------------------------------------------------------------
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