Hi ,
I am using sles9 sp1 rc5 (2.6.5-7.139 kernel)
NFS server is running on a machines.
Client access server and does moderate amount
of io on mounted filesystem.
When nfs server switches to other machine ,
nfs client has to wait for 2-3 minutes so as
to continue io on new nfs server.
Sometimes client sees delay of 20-30
seconds only.Why is this difference seen in
different runs/executions.
Is this the expected behaviour ?
thanks,
kiran
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> I am using sles9 sp1 rc5 (2.6.5-7.139 kernel)
> NFS server is running on a machines.
> Client access server and does moderate amount=20
> of io on mounted filesystem.
> When nfs server switches to other machine ,=20
> nfs client has to wait for 2-3 minutes so as
> to continue io on new nfs server.
> Sometimes client sees delay of 20-30
> seconds only.Why is this difference seen in
> different runs/executions.
> =20
> Is this the expected behaviour ?
i'm speculating, but i expect the delay is due to the time it takes the
client TCP layer to reconnect to the new server host. i notice when a
client loses a TCP connection to a server (even without a failover) it
takes as long as 2-3 minutes to reconnect. it's on my list of things to
look at improving.
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Hi ,
But client displays message "nfs server not
responding" even if following messages are
given by rpcinfo.
#rpcinfo -u <server> 100003
program 100003 version 2 ready and waiting
program 100003 version 3 ready and waiting
program 100003 version 4 ready and waiting
#rpcinfo -t <server> 100003
program 100003 version 2 ready and waiting
program 100003 version 3 ready and waiting
program 100003 version 4 ready and waiting
Should rpc calls over tcp respond if server
is not available
thanks,
--kiran
--- "Lever, Charles" <[email protected]> wrote:
> > I am using sles9 sp1 rc5 (2.6.5-7.139 kernel)
> > NFS server is running on a machines.
> > Client access server and does moderate amount
> > of io on mounted filesystem.
> > When nfs server switches to other machine ,
> > nfs client has to wait for 2-3 minutes so as
> > to continue io on new nfs server.
> > Sometimes client sees delay of 20-30
> > seconds only.Why is this difference seen in
> > different runs/executions.
> >
> > Is this the expected behaviour ?
>
> i'm speculating, but i expect the delay is due to
> the time it takes the
> client TCP layer to reconnect to the new server
> host. i notice when a
> client loses a TCP connection to a server (even
> without a failover) it
> takes as long as 2-3 minutes to reconnect. it's on
> my list of things to
> look at improving.
>
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> Hi ,=20
> But client displays message "nfs server not=20
> responding" even if following messages are=20
> given by rpcinfo.
> =20
> #rpcinfo -u <server> 100003
> program 100003 version 2 ready and waiting
> program 100003 version 3 ready and waiting
> program 100003 version 4 ready and waiting=20
>=20
> #rpcinfo -t <server> 100003
> program 100003 version 2 ready and waiting
> program 100003 version 3 ready and waiting
> program 100003 version 4 ready and waiting=20
>=20
> Should rpc calls over tcp respond if server
> is not available
on TCP connections, the client will report "server not responding" when
it hasn't received a reply from the server after a major timeout.
you'll get one of these messages for every RPC request that has timed
out.
if the client hasn't managed to establish a new connection yet, then,
yes you can expect to see the rpcinfo results like the above and still
have a delay in response. the RPC client can't send RPC requests or
receive replies until a TCP connection has been established with the
server. that can take a while; SYN retries have an exponential backoff.
i've also seen the case where the connection state remains on both sides
after a network partition, but the client's network layer is just
hanging onto the byte stream. the RPC client retransmits, but the
client's network layer buffers the requests. i imagine that the network
layer is also retransmitting the bytes, but because of exponential
backoff, it is waiting a long time before retrying.
some experts say the best thing to do in this case is for the client to
tear down it's connection and simply retry to connect. that may result
in faster recovery from server reboot/failover or network partition, but
it also has some disadvantages.
> --- "Lever, Charles" <[email protected]> wrote:
> > > I am using sles9 sp1 rc5 (2.6.5-7.139 kernel)
> > > NFS server is running on a machines.
> > > Client access server and does moderate amount=20
> > > of io on mounted filesystem.
> > > When nfs server switches to other machine ,=20
> > > nfs client has to wait for 2-3 minutes so as
> > > to continue io on new nfs server.
> > > Sometimes client sees delay of 20-30
> > > seconds only.Why is this difference seen in
> > > different runs/executions.
> > > =20
> > > Is this the expected behaviour ?
> >=20
> > i'm speculating, but i expect the delay is due to
> > the time it takes the
> > client TCP layer to reconnect to the new server
> > host. i notice when a
> > client loses a TCP connection to a server (even
> > without a failover) it
> > takes as long as 2-3 minutes to reconnect. it's on
> > my list of things to
> > look at improving.
> >=20
>=20
> __________________________________________________
> Do You Yahoo!?
> Tired of spam? Yahoo! Mail has the best spam protection around=20
> http://mail.yahoo.com=20
>=20
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--- "Lever, Charles" <[email protected]> wrote:
1 if the client hasn't managed to establish a new
2 connection yet, then, yes you can expect to see the
3 rpcinfo results like the above and still
4 have a delay in response. the RPC client can't send
5 RPC requests or receive replies until a TCP
6 connection has been established with the
7 server. that can take a while; SYN retries have an
8 exponential backoff.
-------
I didnt quiet get the line 3-8 .
What i undestand is that connection is not
established but still rpc request returns info
which should appear only if connection is existing.
How can rpc request return success if connection
through which it passes does not exist ?
thanks ,
kiran
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