[SGVLUG] Samba performance issue

[Matt Campbell]

Hi Claude,

That this is due to a thermal recal is exactly what I have been fearing all
along.  I have been building media arrays for about 2 decades now and the
drive BIOS tuned for A/V has always been a closely guarded mystery.  There
were AV versions of the 1T drives I chose for the server, but they were
considerably more expensive and not available through regular channels.  I
had heard that modern drives with larger buffers were 'good enough' for
media systems, so I opted for the 'cheaper' method and I am mortally afraid
that this is rising to strike my nether bits.

Other than writing a test a'la Dan to quantify my problem what are other
ways I can look to tune the system I have?

I am using 16M cache 7200RPM 1T Seagate drives in groups of 4 using software
Linux RAID 3 via the md driver.

I had trouble with the first couple of SATA RAID cards I looked into, but I
am reasonably happy with the ones I ended up with:  3 x Adaptec 3Gb 2 port
PCIe cards plus 4 MOBO SATA 3Gb ports.

Temperatures run high with 10 drives in the case, but it is a SuperMicro
server case with mega fans (burned out my first power supply as they suck
about 1.4 amps total!  Sucked the fan bus dry on my Antec Trio 650 3 bus
mega power supply), but I have been monitoring the drives via SMART
(reference the graph on one of my previous posts) and they are doing
reasonably well.  I don't know how hot they are supposed to get by I'm
freezing my wife out by keeping the AC on full time.  My office doesn't get
above 74'F.

I checked the latest graph I ran and the highest reported drive temps were:
69c - 190_Temperature_Celcius
41c - 194_Temperature_Celcius
Variation was +0-10c on each of those numbers.

The system tests good for streaming HD all day long, but playing SD I get
these glitches.  I was able to stream uncompressed SD (about 1.5 times the
compressed HD data rate) with no problems over the 1000T network, but was
still getting these glitches.  I assume it is due to my file sharing setup
or the SMB protocols.

So where should I start?
- Changing the Samba setup
- Changing the software RAID setup
- Changing the filesystem buffers
- Looking at drive performance
- Looking at client performance
- Looking at server memory useage
- Looking at server CPU loading
- Looking at server IO loading
- something else?

I feel kind of funny asking the professionals on this list for free help
when that is what they make their money at, but this is for my family's
media server, not something I had been planning on using to make money, at
least until last weekend when it was pressed into service during an
emergency and fell flat on its face.  On the other hand this is a "user's
group" ;)

Thanks again for any suggestions on what to look for or where to start.

Matt

P.S.  Don't let my use of high falutin' terms fool you.  I worked for IBM
for a number of years doing Unix OS architecture, but I've been in Hollywood
the last 15 years and am *way* out of date.  I tried to jump back into Linux
and found the rules had been rewritten while I was sleeping.  I know the
theory and history, but all the tools I reach for have been moved and
renamed by mischievous elves.  Assume I'm a complete newbie and let me know
what the obvious things are that I have missed.  ;)

> -----Original Message-----
> From: sgvlug-bounces at sgvlug.net [mailto:sgvlug-bounces at sgvlug.net] On
> Behalf Of Claude Felizardo
> Sent: Wednesday, May 21, 2008 6:32 PM
> To: SGVLUG Discussion List.
> Subject: Re: [SGVLUG] Samba performance issue
> 
> On Wed, May 21, 2008 at 4:44 PM, Matt Campbell <dvdmatt at gmail.com>
> wrote:
> >
> > Good afternoon,
> >
> > My media server project is coming along well, I have purchased an
> Apple TV
> > and am hacking it with Linux to act as the client (fall meeting
> topic?).
> >
> > I have been running into some performance problems using Windows as
> the
> > client.  The Samba server on the Linux platform can spool media all
> day, but
> > every 20 minutes or so there is a .5 second hiccup.  Do any of you
> have
> > experience tuning a Linux server to remove these problems?
> 
> Could it be thermal recalibration of the hard drives?  What brand and
> models?  What temp are the drives running at?   What temperature is
> your office and the computer?
> 
> I remember that the first TiVo's used a specific brand/model that were
> "A/V" rated that were suppose to schedule the recalibration to when a
> platter was not being accessed.
> 
> http://en.wikipedia.org/wiki/Av_drive
> http://stason.org/TULARC/pc/pc_hardware_faq/3_14_What_is_Thermal_Recali
> bration.html
> http://www.pcguide.com/ref/hdd/op/actRecal-c.html
> 
> When I hacked my first TiVo by replacing the original 30 GB drive with
> an 80 GB, this was a frequent topic of discussion but it's been a
> while since I've looked at this.  According to one TiVo hacking supply
> website, they offer drives that have been tuned for DVR use.  They
> don't say exactly what they have done other than they use tools or
> procedures that have been approved by the drive manufacturer.
> 
> What kind of RAID configuration are you running?  Perhaps you could
> use more memory to increase the number of buffers?
> 
> claude