[mythtv-users] Raid Performance Tweaking

[Dean Wilson]

In my case, the mythbox is also hosting a web and email server, and is
acting as a firewall for all the internal computers.  I also have two
high def, and one standard def tuners, which frequently all record at
the same time.  So there's plenty of disk read/writes, which seems to
be slowing playback down.

In using it with 5 disks configured with Raid5, (which, to my
understanding, is slower to write to than when writing to a single
disk, since it has to write additional parity bits to the nth drive) I
noticed that HD playback stuttered any time that it was also recording
another HD show.  I had DMA turned on, but haven't been able to get
past my playback issue when the drives were being written to.  I'm
currently reconfiguring my system anyway, so I thought I'd run the
test to see which configuration worked best.

(The rest of my system shouldn't be suspect, as it's an AMD X2 4200+
with 1GB ram.)

Any other configuration thought/suggestions would be welcome...
~Dean

On 7/6/06, Debabrata Banerjee <davatar at comcast.net> wrote:
> Whatever you do it's going to be irrelevant for mythtv unless you add a
> massive amount of tuners. Unless you decide to make a RAID array out of 4GB
> dis\ks from 1996.. Even one disk should be good for many streams of video.
> Let's not confuse Mbit and MBytes, as people often do.
>
> ----- Original Message -----
> From: "John Drescher" <drescherjm at gmail.com>
> To: "Discussion about mythtv" <mythtv-users at mythtv.org>
> Sent: Thursday, July 06, 2006 5:06 PM
> Subject: Re: [mythtv-users] Raid Performance Tweaking
>
>
> >I think the problem here is that guide is very outdated. Did you see the
> > computer they were using "Dual Pentium Pro 150 MHz"? I bet that was on
> > a 2.2kernel also so to me any numbers there are meaningless. At work I
> > use 256K
> > or 512K blocks on my 1TB or 2TB raid 5 or raid 6 arrays. My latest server
> > build featured 6 X 320 GB seagate 7200.10 drives in a raid 6 256K clusters
> > for ~ 1.2TB of raid space. With that setup on a Athlon64 M2 3200 system
> > (asus mobo) I get ~260 MB/s on the non cached hdparm benchmark.
> >
> > John
> >
> > On 7/6/06, Dean Wilson <dean.k.wilson at gmail.com> wrote:
> >>
> >> I know that many of us are interested in Raid, but don't really know
> >> the best configuration for a myth setup.  I, like many others here, am
> >> interested in Raid5, and would like it to perform optimally for (very)
> >> large files.
> >>
> >> I've read http://www.tldp.org/HOWTO/Software-RAID-HOWTO-9.html, which
> >> gets into chunk and block size performance testing, but doesn't use
> >> chunks above 32K.  I would think that a larger chunk size would be
> >> ideal for myth, as it uses exceedingly large files.
> >>
> >> I figured I'd use bonnie to measure performance gains/losses, since
> >> that's what the howto used.  Obviously I'll play with different
> >> chunk/block size combinations, and will report my findings.  But I'm
> >> curious to know if anyone out there would be interested in any other
> >> specific tests?  If so, let me know -- I'll try to include them, and
> >> will put together a web page with the results I find.
> >>
> >> Thanks,
> >> ~Dean
> >> _______________________________________________
> >> mythtv-users mailing list
> >> mythtv-users at mythtv.org
> >> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
> >>
> >
>
>
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