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

[Manuel Wolfshant]

On 02/09/2011 11:47 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

Can you please check that the drives are seen by the system via the SCSI 
( as opposed to older PATA ) protocol ? The BIOS must be configured to 
avoid legacy/compatible mode by all means ( and use AHCI instead )