[mythtv-users] OT: SMB performance?

Gary Buhrmaster gary.buhrmaster at gmail.com
Thu Jan 19 21:53:11 UTC 2012


On Thu, Jan 19, 2012 at 21:22, Ben Kamen <bkamen at benjammin.net> wrote:
....
> The CentOS box is the only one I can't set to 9K -- and for fun, I did set CentOS and my Windows box to something that matched and it just doesn't work so well.

The adapter/driver is going to determine the max frame size.
4470-4500 was "popular" for some vendors at one point.
1548 was the "baby jumbo" for some low end switches
(to pass q-in-q tagged frames I think).  Realtek has
their 7K size.  Generically, the value 9K is what most
people mean by "jumbo capable" these days.

The primary purpose for jumbo frames is to reduce
the royal overheads of network process.  With advanced
TOE (TCP Offload Engine) capability in many cards
(which included interrupt coalescence, large segment
offloading, ip checksumming), the advantage of the
jumbo frames was reduced in practice (the OS
now only sends/receives large chunks).  Another
advantage of jumbo frames comes with long-haul
circuits and the slow start/recovery algorithms.  These
really do not apply to your local LAN (where the RTT
is fractions of milliseconds).

Gary


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