Re: NFS mount lockups since about a month ago

[Roger Heflin]

Make sure you have sar/sysstat enabled and changed to do 1 minute samples.

sar -d will show disk perf.  If one of the disks "blips" at the
firmware level (working on a hard to read block maybe), the util% on
that device will be significantly higher than all other disks so will
stand out.  Then you can look deeper at the smart data.

sar generically will show your cpu/system time and sar -n DEV will
show detailed network traffic, sar -n EDEV will show network errors.

With it set to 1 minute you should be able to detect most blips.

On Sun, Sep 26, 2021 at 10:26 AM Jamie Fargen  wrote:
> Are there network switches under your control? It sounds similar to what happens when MTU on the systems MTU do not match or one system MTU is set above the value on the switch ports.
>
> Next time the issue occurs use ping with the do not fragment flag.
> ex $ ping -m DO -s 8972 ip.address
>
> This example should be the highest value to work in the case of MTU size 9000, there is 28 byte overhead for IPv4 packets.
>
> Second, are you sure no one is attaching to the network and duplicating the MAC address of your NFS server or perhaps the system that is stalled? If the switches are manageable you would have to insure that the MAC addresses are being learned on the correct ports.
>
> -Jamie
>
> On Sun, Sep 26, 2021 at 10:24 AM Tom Horsley  wrote:
> > On Sun, 26 Sep 2021 10:26:19 -0300
> > George N. White III wrote:
> > > If you have cron jobs that use a lot of network bandwidth it may work
> > > fine until some network issue causing lots of retransmits bogs it down.
> >
> > Which is why you should check the dumb stuff first! Has a critter
> > chewed on the ethernet cable to the server?
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