Hi Michael,
Sorry to bother you with so many questions. Looks like a state machine takes a
step forward only in the test or testsome function calls and multiple state
machines continue in a round-robin way. Why does not PVFS2 spawn a thread for
each state machine? I feel this way can ensure the continuous running of a
state machine and as a result, improve performance.
Appreciate for your patience.
Wantao
------------------ Original ------------------From: "Michael
Moore"<[email protected]>;
Date: Thu, Jun 30, 2011 01:13 AM
To: "Wantao"<[email protected]>;
Cc: "pvfs2-users"<[email protected]>;
Subject: Re: [Pvfs2-users] Number of data transfer messages
On Wed, Jun 29, 2011 at 10:01 AM, Wantao <[email protected]> wrote:
Hi Michael,
Your reply helps me a lot. From the source code, I see that a flow has 8
buffers, and each buffer is 256KB. Does that mean each flow can transfer at
most 8 messages, each message is 256KB? If that is true, what happens to a file
larger than 2MB(8*256KB)?
Glad to help. The buffers are re-used as data is transferred; it just means
that a single flow will have at most that much data at anytime buffered to
transfer. The size of the buffer is configurable via FlowBufferSizeBytes and
FlowBufferPerFlows if you have a specific need to tune them.
Michael
Thanks,
Wantao
------------------ Original ------------------
From: "Michael Moore"<[email protected]>;
Date: Wed, Jun 29, 2011 08:06 PM
To: "Wantao"<[email protected]>;
Cc: "pvfs2-users"<[email protected]>;
Subject: Re: [Pvfs2-users] Number of data transfer messages
Hi Wantao,
In the situation you describe a single request will be sent to each server for
your application's I/O request. When accessing a file the client needs to know
what datafile handles are associated with the file, done via a getattr request,
after that the client can perform I/O without contacting the metadata server.
However, if the client updates attributes (atime, mtime, etc) as typically
happens when using the kernel client interface, there will be a setattr request
to the metadata server.
Hope that helps,
Michael
On Wed, Jun 29, 2011 at 3:20 AM, Wantao <[email protected]> wrote:
Hi, all
I have a PVFS2 installation with three IO servers and 64KB strip size. my
application requests 256KB in one IO operation(read or write). So, it needs two
continuous strips from server1 and one strip from server 2 and 3. In this case,
how many data transfer messages are needed for server1? Can it send or receive
two strips in one message? Another question is that when accessing a big file,
does PVFS2 need to interact with meta server for each IO operation?
Thanks for all advice.
Wantao
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