[CentOS] slow NFS speed
grimme at atix.de
Wed Jul 30 20:41:10 UTC 2008
On Wednesday 30 July 2008 20:52:07 John R Pierce wrote:
> Mag Gam wrote:
> >> 70-80Mb/sec.
> > MB, sorry :-)
> thats on the order of 700-800Mbit/sec, which is quite good for a single
> session on GigE. as others have said, the sort of bonding you're doing
> doesn't speed up single transfers, instead it helps with multiple
> concurrent sessions.
I would not agree that if you are using round-robin (mode 0) bonding that it
does not scale with one session. I would say it should or must scale:
1780 balance-rr: This mode is the only mode that will permit a single
1781 TCP/IP connection to stripe traffic across multiple
1782 interfaces. It is therefore the only mode that will allow a
1783 single TCP/IP stream to utilize more than one interface's
1784 worth of throughput. This comes at a cost, however: the
1785 striping generally results in peer systems receiving packets
1786 of order, causing TCP/IP's congestion control system to kick
1787 in, often by retransmitting segments.
That means it could if we forget about out of order delivery.
What I see in a project where we have bonded four nics together with rr is
that the way out is "evenly" loaded over the four nics (although we are
communicating with only two hosts). But the way back is still the problem.
Cause all packets arrive at only one nic. Again this is explained by
1818 This mode requires the switch to have the appropriate ports
1819 configured for "etherchannel" or "trunking."
And I also remember that I read that you can configure the etherchannel
balancing. That means the way back. Some switches by default spread the
packets going back by the MAC-Address (that's what we are seeing). But there
should also be other balancing modes for a etherchannel. Got it here it is:
211 If ARP monitoring is used in an etherchannel compatible mode
212 (modes 0 and 2), the switch should be configured in a mode
213 that evenly distributes packets across all links. If the
214 switch is configured to distribute the packets in an XOR
215 fashion, all replies from the ARP targets will be received on
216 the same link which could cause the other team members to
What we have done is first measure the possible load over the network (with nc
without any local i/o involved for example) and then you have a bottom line.
Next see what nfs can do.
BTW. I didn't write the bonding.txt but it appears to be dealing with some
topics discussed here.
BTW. from FS point of view it should not be a problem to get some 200MByte/sec
out of a bunch of disks (depending on the speed and cache of the disks and
the bus where the data goes through).
Gruss / Regards,
More information about the CentOS