[ubuntu] Slow disk writes on Ubuntu, but blazing fast on Knoppix?

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http://ubuntuforums.org – My brand-new Ubuntu desktop (12.04 LTS) has extremely slow write speed (1 MB/sec) on all its hard drives. However, if I boot on Knoppix 7.2 (kernel 3.9), the speed on all drives is immediately fixed, increasing to 100 MB/sec. Can anybody help me fix the speed under Ubuntu? The slowness happens on an internal Western Digital HD, an internal SSD RAID pair (3ware RAID card), and external hard drives using USB 3.0, Firewire, and eSATA, all using ext4. Literally every storage device I can connect. I also tried Ubuntu 13.04 and (prerelease) 13.10 Live CDs on the same system, and they had the same (Hardware)