Hi folks!
I have been trying to use a
RAID bus controller: Silicon Image, Inc. PCI0680 Ultra ATA-133 Host
Controller (rev 02)
to create a RAID0 workspace for MythTV, but it's not working right....
I have two Seagate 160gb drives in a RAID 0 array on an SiI0680 PCI
ATA raid controller. I formatted an XFS filesystem on
/dev/mapper/sil_agbgdgbjfhei2,
and set mythbackend to use it. ( My DVB card is a DviCO
Fusion Gold 3,( Conexant CX23880).)
When I watch live MythTV, 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 ( /dev/hdc1 ), performance is acceptable.
The RAID devices are hde and hdg, the/ partition is hdc.... to me this looks
like all my physical drives give comparable throughput. This is what hdparm
reports:
/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/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
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).
So, given the same hardware throughput, I would expect better performance
with the XFS+RAID setup. This is not the case. 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.
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
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