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 >> >> >> >> _______________________________________________ >> Pvfs2-users mailing list >> [email protected] >> http://www.beowulf-underground.org/mailman/listinfo/pvfs2-users >> >> > ** >
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