[mythtv-users] NFS and remote backend

Yeechang Lee ylee at pobox.com
Fri Jan 11 18:08:33 UTC 2008

Steven Adeff <adeffs.mythtv at gmail.com> says:
> this isn't much help, but I noticed the same thing. NFS transfers
> are painfully slow and actually eat up a lot of "overhead" whereas
> FTP uses the full bandwidth and doesn't seem to eat up "overhead".


> So there is definitely something wrong with the base setup of NFS
> somewhere. I couldn't figure out what, but at least I'm not the only
> that noticed this problem.

As I've commented here several times over the past two+ years I've
been running MythTV, CIFS works great for transfers of the large,
multi-gigabyte files MythTV uses, while NFS's performance is abysmal
by comparison. NFS's lengthy delays in dropping connections (even with
soft and intr specified) and consequent hangs are annoying, too.

I use an MTU of 3136 (1024*3+64) as a value in this range is optimal
for my particular SMC 8508T gigabit router, according to the
University of Wisconsin-Milwaukee's benchmarks.

Other settings:

	options cifs CIFSMaxBufSize=114688

media	-fstype=cifs,username=mythtv,password=mythtv,rsize=114688,wsize=57344,forcedirectio,ttl=100     ://SERVER/MEDIA

Both RAID arrays my signature mentions are mounted this way. When I
have each box mount the other's array, I get simultaneous
bidirectional 25-35MB/s write speeds on a simple 'dd' benchmark with
10GB test files.

I'm sure additional optimization is possible and would appreciate
suggestions, but the performance is sufficient my needs and b) is far
superior to anything I've ever been able to achieve via NFS. And yes,
I've tried everything under the sun, thank you.

Frontend/backend:	P4 3.0GHz, 1.5TB software RAID 5 array
Slave backend:		Quad-core Xeon 1.6GHz, 6.6TB sw RAID 6
Video inputs:		Four high-definition over FireWire/OTA
Accessories:		47" 1080p LCD, 5.1 digital, and MX-600

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