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Date:      Wed, 20 Feb 2008 13:30:13 -0800
From:      Chuck Swiger <cswiger@mac.com>
To:        Alfred Perlstein <alfred@freebsd.org>
Cc:        "freebsd-performance@freebsd.org" <freebsd-performance@freebsd.org>, Valerio Daelli <valerio.daelli@gmail.com>
Subject:   Re: Bad performance of 7.0 nfs client with Solaris nfs server
Message-ID:  <B4337B98-B9A2-40A2-9C85-1BCC3F5FB54F@mac.com>
In-Reply-To: <20080220210118.GY99258@elvis.mu.org>
References:  <27dbfc8c0802190243y113d3059yd0c602850a4dbd6b@mail.gmail.com> <47BB33AD.1050005@FreeBSD.org> <27dbfc8c0802200323r13f69905l4940d0d5accd1eb1@mail.gmail.com> <9BCE1D41-EC1A-4FE6-8551-E725DBE5D3A8@mac.com> <20080220210118.GY99258@elvis.mu.org>

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On Feb 20, 2008, at 1:01 PM, Alfred Perlstein wrote:
>> Take a look at the level of packet fragmentation you are  
>> encountering;
>> yes, this is expected and things will work but there is extra latency
>> added when the IP stack has to reassemble packets before the data can
>> be delivered.  Try setting the NFS rsize/wsize to 1024 or perhaps  
>> 1400
>> and see whether that improves performance.
>>
>> Or, if your switch and NICs support it, see whether you can get Gb
>> Ethernet jumbo frames working so that you don't have to fragment for
>> 2K or 4K data packets....
>
> TCP mounts do not have this problem.  You can safely use
> 32k or higher sizes with TCP without fragmentation.

Oh, sure.  But there is a bit more overhead with TCP transport than  
UDP-- for local (switched) networks, UDP generally seems to be a  
win...TCP seems to be a better choice over a VPN or some similar kind  
of WAN.

-- 
-Chuck




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