[mythtv-users] Slow video on XFS raid 0, ok video on ext3 on single drive.
listbox at hymerfania.com
Sun Dec 31 07:04:07 UTC 2006
The RAID devices are hde and hdg, the/ partition is hdc.... to me this looks
like all my physical drives give comparable throughput.
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
Timing buffered disk reads:
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
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
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
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?
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
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
> 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!
> mythtv-users mailing list
> mythtv-users at mythtv.org
Please use hdparm -tT to benchmark the speed of your drives, and your raid
hdparm -tT /dev/sda /dev/sdb /dev/sdc /dev/md0
You should do this when the system is idle, perhaps even in single user
That should shed some light on the situation.
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