[mythtv-users] OT: SMB performance?

Ian Clark mrrooster at gmail.com
Fri Jan 20 18:27:13 UTC 2012


On 20 January 2012 15:33, Gary Buhrmaster <gary.buhrmaster at gmail.com> wrote:
> On Fri, Jan 20, 2012 at 06:00, Ian Clark <mrrooster at gmail.com> wrote:
> ....
>> I get about 40MB/sec to/from my samba box to my win7 box, which I
>> think is about the max my network supports (iftop watching a very
>> simple client/server sending data across a socket seemed to indicate
>> this speed too.)
>
> iperf tends to be the tool of choice for measuring raw
> network performance.

Thank you, I didn't know about that. That's quite a handy little tool.

> Most modern mainstream processors
> (with reasonable ethernet cards :-) can get quite close
> to line rates on a LAN with little additional work (WAN
> high speed transfers are outside of scope here).  For
> a gigabit network, you should see closer to 100MB/sec
> (mid 90's at least).

I had forgotten, but the quoted speeds were when I was trying to track
down some network issues I was having. They were for and onboard
realtek NIC that turned out to have... issues.

Just used iperf and I see about 670Mbit from win7 to the server,
rising to around the 815 mark if I enable 4k jumbo frames (I can't
enable any larger as NetBSD is maxing out at 9000 and the win driver's
next step is 9014.) I suspect if I could enable the offload features
of the nic on the server it would go a little faster. (my current
setup prevents this. )

Interestingly I see about 362Mbit from my mythbox to the same server
(same network), rising to around the 460 mark if I enable 4k jumbo
frames.

The myth box has a cheap and nasty Realtek 8169 based PCI card in it,
the Windows box has a PCI intel card. It does appear you get what you
pay for. :)

As I can't run with jumbo frames (due to another switch not supporting
them) I'll have to stick with /only/ 600 Mbit. ;)

> However, iperf says nothing about
> application or system bottlenecks.  All too many protocols
> have a "request, (wait), receive, (acknowledge)" cycle which
> leaves lots of wasted (idle) time.  And if a disk has to seek
> to read data, that can slow down the effective transfer
> speeds.  Parallel transfers can help in some cases, but
> may have bad interactions in others (such as when that
> causes the disk to seek from file A to file B every other
> request; seeks kill performance).
>
Agreed, the above speeds still only give me about 40MB sec in general
with samba, mainly due to the read/write speed of the HD in my win
box. :)

Ian


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