How do I make CentOS run SATA drives at 3Gb/s at boot?
Background:
I'm having an issue with a motherboard that claims to support 6Gb/s SATA transfer speeds, but when using 4 drives on it, in a software RAID 10 with heavy disk IO, some of the SATA links start throwing kernel errors, ie. ata1.00: failed command: WRITE FPDMA QUEUED. But it's a different drive each time, not always ata1, and running extended test on each disk individually produces no errors.
When the errors occur, the Kernel/OS (CentOS 6.2) eventually resets the link several times, and when it continues to fail, then it changes the link speed to 3Gb/s. Once that happens, the errors stop for that drive for the remainder of the session.
What I'd like to do is tell the OS to set the SATA links to 3Gb/s to start with on boot, since I don't think the motherboard's SATA bus can handle all 4 drives at 6Gb/s. I couldn't find an option in the Motherboard's BIOS to change the link speed.
Questions:
How would I go about doing that? ie. a config file?
Can it be done while the system is running with the RAID array assembled and root partition mounted, or do I need to boot from a rescue CD?
Will this result in any data loss? I have backups of course, but reinstalling/restoring is several hours of work that I'd like to avoid if possible.
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