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

[solarflow99]

you know, I wonder if there is a chance it could be the CPU bug that
was just reported?  I had a PC with an i5 that had very poor
performance, once reverted to an older release it wasn't as
noticeable.



On Thu, Feb 10, 2011 at 5:39 AM, Matthias Saou
<thias at spam.spam.spam.spam.spam.spam.spam.egg.and.spam.freshrpms.net>
wrote:
> William Warren wrote :
>
>> On 2/9/2011 4:47 AM, Matthias Saou wrote:
>> > 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...
>> >
>> are you using the bios raid or MD raid?  If you are using biod raid you
>> are running everything effectively pio mode and it's going to suck.  Put
>> the bios in ahci(not raid mode) and then use Linux raid from inside the
>> partitioning scheme(which is md raid) i bet performance will be much better.
>
> I probably forgot to detail, but it's indeed MD RAID I'm using. No one
> in their right mind would use one of those cheap motherboard pseudo
> RAID, would they? :-)
>
> Anyway, I've reinstalled the server with RHEL5 and it's running fine
> now. Definitely something going on between this particular hardware and
> RHEL6.0... since I intend to use it only as a KVM hypervisor, and that
> RHEL6 still doesn't support the new cool stuff that would make a
> difference (like KSM), I'll stick with RHEL5, even though all of the
> virtual servers running under it will be RHEL6.
>
> Matthias
>
> --
> Clean custom Red Hat Linux rpm packages : http://freshrpms.net/
> Fedora release 14 (Laughlin) - Linux kernel 2.6.35.10-72.fc14.x86_64
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>
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