[mythtv-users] Raid Performance Tweaking

[yan]

Dean Wilson wrote:
> 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.
SCSI, SATA, or IDE drives?  If they're IDE, is each one on its own 
controller?

I have a RAID of 4 ide drives on two controllers, two tuners, and the 
only time I have problems is if the system is also running 2 transcoding 
jobs.  All other stuff, including swap and OS, reside on a RAID5 scsi array.

You may also be seeing a PCI bus saturation; have you figured out if 
your PCI bus can sustain all those data transfers?

Me, I'm lucky; my backend is on an old 64bit PCI server mobo...  So I 
can get away with 1GHz CPUs without any problems.

--Yan