Re: RAID performance - new kernel results

[Roy Sigurd Karlsbakk <roy@karlsbakk.net>]

> > I suspect that the single ping packets being lost are an indication
> > of a
> > problem, but this should not impact the users (TCP should look after
> > the
> > re-transmission, etc). Wether this is related to the longer 10-50
> > second
> > outage I'm not sure.
> 
> No, single lost pings are *not* a sign of a problem. It is perfectly
> normal for a network to have random traffic spikes that fill a
> switch's
> store-and-forward buffers. ICMP pings are *datagrams*, like UDP, so
> they aren't retransmitted when dropped. Losing them as infrequently as
> you say suggests your network isn't heavily loaded.

Switches (unlike bridges) do not use store-and-forward. They use cut-through, meaning they use store-and-forward for the initial packet from A to B and then store the path and switch it later, sniffing the MAC addresses and just use pass-through.

As was said, the traffic on the network was minimal, so I really doubt this had an impact. Getting 30 seconds+ of drops must come from a bad network stack or a really bad switch, but then again, two switches were tested, so I doubt the switches alone could do that.

What may be doing it, is bad (or perhaps incompatible) bonding setup.

Vennlige hilsener / Best regards

roy
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Roy Sigurd Karlsbakk
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