[rhelv6-list] Performance issues with RHEL6 (iowait)

[Matthias Saou]

Hi,

I just got this isolated RHEL6 server, with hardware I've never used
before. It's a Supermicro X8STi motherboard (Xeon i7 920) with two cheap
SATA disks (WD10EADS-00P8B0) using software RAID-1.

The system is unusable : A quick strace of various processes shows very
long waits during many different I/O related calls such as open, read,
pread, stat, fdatasync...

I've tried failing every other partition in order to be sure to use only
one disk for a while, with the same results. Running RAID rebuilds
sometimes peaks at 60-100MB/s but very rarely. Right now for instance,
the main 900GB RAID-1 is rebuilding from sda2 to sdb2 and it's
reporting 400kB/s with system load of over 2 (the server is idle apart
from this rebuild). While this is going on, even smartctl on sdb takes
time to respond. When no rebuild is in progress, the problems are the
same.

I'm using the latest released 2.6.32-71.14.1.el6.x86_64 kernel, and
here is the detail of the SATA controller(s) :

00:1f.2 IDE interface: Intel Corporation 82801JI (ICH10 Family) 4 port
SATA IDE Controller #1 Subsystem: Super Micro Computer Inc Device 0009
	Kernel driver in use: ata_piix
	Kernel modules: ata_generic, pata_acpi, ata_piix
00:1f.5 IDE interface: Intel Corporation 82801JI (ICH10 Family) 2 port
SATA IDE Controller #2 Subsystem: Super Micro Computer Inc Device 0009
	Kernel driver in use: ata_piix
	Kernel modules: ata_generic, pata_acpi, ata_piix

No errors reported by the kernel apart from some processes stuck for
more than 120s before the last reboot. Has anyone seen disk I/O issues
like this with RHEL6 and similar hardware?

Matthias

PS: A possibly important detail is that this is a server provided by
ovh.com which has been offering RHEL6 for a while but still has it
marked as "BETA" (it's not the RHEL6 beta, it's how they consider their
offering of RHEL6), which might indicate known problems between their
typical hardware and RHEL6. I didn't find any clues with a quick
bugzilla search...

-- 
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