[mythtv-users] Slow video on XFS raid 0, ok video on ext3 on single drive.
Justin Piszcz
jpiszcz at lucidpixels.com
Sun Dec 31 12:05:24 UTC 2006
Good old PCI limits you to 133MB/s maximum, typical throughput read/write
will not exceed that amount, go with a PCI-express system if you need more
read/write bandwidth.
On Sat, 30 Dec 2006, Listbox wrote:
> The RAID devices are hde and hdg, the/ partition is hdc.... to me this looks
> like all my physical drives give comparable throughput.
>
> /dev/hda:
> Timing cached reads: 1668 MB in 2.00 seconds = 834.10 MB/sec
> Timing buffered disk reads: 88 MB in 3.05 seconds = 28.87 MB/sec
>
> /dev/hdb:
> Timing buffered disk reads:
> /dev/hdc:
> Timing cached reads: 1696 MB in 2.00 seconds = 847.36 MB/sec
> Timing buffered disk reads: 88 MB in 3.05 seconds = 28.82 MB/sec
>
> /dev/hde:
> Timing cached reads: 1680 MB in 2.00 seconds = 838.49 MB/sec
> Timing buffered disk reads: 168 MB in 3.03 seconds = 55.46 MB/sec
>
> /dev/hdf:
> Timing cached reads: 1688 MB in 2.00 seconds = 843.57 MB/sec
> Timing buffered disk reads: 164 MB in 3.00 seconds = 54.59 MB/sec
>
> /dev/hdg:
> Timing cached reads: 1696 MB in 2.00 seconds = 846.68 MB/sec
> Timing buffered disk reads: 162 MB in 3.03 seconds = 53.45 MB/sec
>
> So, given the same hardware throughput, I would expect better performance
> with the XFS+RAID setup. This is not the case.
> My adapter is a:
> RAID bus controller: Silicon Image, Inc. PCI0680 Ultra ATA-133 Host
> Controller (rev 02)
> I also tried upping the PCI latency of the RAID card with
> setpci -v -s 01:07.0 latency_timer=B0 # PCI0680 Ultra ATA-133 Host
> But this had no effect. The DVB card has a latency of 32(decimal).
>
> I just reformatted with ext3, and tried again, and got the same degradation.
> It's looking like the RAID is the problem, but I do not,NOT,NOT! want to
> un-stripe the disks.
>
> What else to try?
>
> Listbox
>
> -----Original Message-----
> From: Andrew Lyon [mailto:andrew.lyon at gmail.com]
> Sent: Saturday, December 30, 2006 11:31 AM
> To: Discussion about mythtv
> Subject: Re: [mythtv-users] Slow video on XFS raid 0,ok video on ext3 on
> single drive.
>
> On 12/30/06, Listbox <listbox at hymerfania.com> wrote:
> > Hi folks!
> >
> > I have two Seagate 160gb drives in a RAID 0 array on an SiI0680 PCI
> > ATA raid controller. I formatted an XFS filesystem on a single
> > partition, and set mythbackend to use it. My DVB card is a DviCO
> > Fusion Gold 3,( Conexant CX23880).
> >
> > When I watch live TV, I get terrible artifacts on digital TV, and slow
> > frame rates on analog. When I reset mythbackend to use a ext3
> > partition on a single drive, performance is acceptable.
> >
> > I went to considerable trouble to get the RAID and XFS working on my
> > Fedora
> > 5 system, and it's pretty discouraging to see that it actually
> > degrades instead of enhances performance. What is likely the problem?
> > Is it the controller, the raid or the filesystem?
> >
> > Thanks for any advice!
> >
> > Listbox
> >
> > _______________________________________________
> > mythtv-users mailing list
> > mythtv-users at mythtv.org
> > http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
> >
>
> Please use hdparm -tT to benchmark the speed of your drives, and your raid
> array, e.g.
>
> hdparm -tT /dev/sda /dev/sdb /dev/sdc /dev/md0
>
> You should do this when the system is idle, perhaps even in single user
> mode.
>
> That should shed some light on the situation.
>
> Andy
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