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Sometime ago I posted some performance tweaks for TCP performance, which
(when the filer was switched to TCP) worked a treat. I was hoping to get
the same for UDP. However...
It seems that UDP on Sun over 1GB Ethernet and above is problematic. Some
details below (words and details have been changed to protect the guilty!).
As a result we're sticking to TCP for now.
Peter
=====================================================
I've done a bit of research and found out that testing of a very similar
setup to yours, by another customer, showed that there is a performance bug
in the NFS UDP implementation of Solaris.
We all know that NFS over UDP is about 20% faster than NFS over TCP however,
the Solaris implementation of UDP breaks this rule when gigabit Ethernet is
involved..! It seems to be that when NFS is used with UDP for internet,
10Mb and 100Mb connectivity then the rule applies and also when you have a
gigabit Ethernet connection under low load then again all is fine.
The performance problem appears when you try to load the gig connection
heavily - Solaris's UDP simply cannot perform at the required rate. Now,
thankfully, the TCP implementation in Solaris is very good and is up to the
job - hence, the situation you find whereby NFS over TCP is much better than
NFS over UDP. This matches exactly with your findings where under normal
database usage your Gig + NFS/UDP connection is fine - but when you try to
backup over the Gig Ethernet link the load on the network goes up and UDP
can't perform. You switched from UDP to TCP and the problem went away.
My recommendation to you is to keep using NFS over TCP - the other customer
has decided to stay with TCP as it works well and they can't see any benefit
in moving back to UDP.
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********************** http://www.burallplastec.com ********************
Sometime ago I posted some performance tweaks for TCP performance, which
(when the filer was switched to TCP) worked a treat. I was hoping to get
the same for UDP. However...
It seems that UDP on Sun over 1GB Ethernet and above is problematic. Some
details below (words and details have been changed to protect the guilty!).
As a result we're sticking to TCP for now.
Peter
=====================================================
I've done a bit of research and found out that testing of a very similar
setup to yours, by another customer, showed that there is a performance bug
in the NFS UDP implementation of Solaris.
We all know that NFS over UDP is about 20% faster than NFS over TCP however,
the Solaris implementation of UDP breaks this rule when gigabit Ethernet is
involved..! It seems to be that when NFS is used with UDP for internet,
10Mb and 100Mb connectivity then the rule applies and also when you have a
gigabit Ethernet connection under low load then again all is fine.
The performance problem appears when you try to load the gig connection
heavily - Solaris's UDP simply cannot perform at the required rate. Now,
thankfully, the TCP implementation in Solaris is very good and is up to the
job - hence, the situation you find whereby NFS over TCP is much better than
NFS over UDP. This matches exactly with your findings where under normal
database usage your Gig + NFS/UDP connection is fine - but when you try to
backup over the Gig Ethernet link the load on the network goes up and UDP
can't perform. You switched from UDP to TCP and the problem went away.
My recommendation to you is to keep using NFS over TCP - the other customer
has decided to stay with TCP as it works well and they can't see any benefit
in moving back to UDP.
******************************* Disclaimer *****************************
Confidentiality: This e-mail and any attachments are intended for the
addressee(s) only and may be confidential. If they have come to you in
error you must take no action based on them, nor must you copy or show
them to anyone; please reply to this e-mail and highlight the error.
Viruses: Although we have taken steps to ensure that this e-mail and
attachments are free from any virus, we advise that in keeping with good
practice the recipient should ensure they are actually virus free.
********************** http://www.burallplastec.com ********************