debug HDD performance on Ubuntu server

Hello, we got a following system running as file server: Ubuntu server Intel SE7230NH1-E Intel SRCU-42E 512MB PCIe SCSI controller The problem is as follows: /dev/sdb: Timing cached reads: 2258 MB in 2.00 seconds = 1129.32 MB/sec Timing buffered disk reads: 478 MB in 3.01 seconds = 158.65 MB/sec /dev/sdc: Timing cached reads: 2202 MB in 2.00 seconds = 1101.75 MB/sec Timing buffered disk reads: 106 MB in 3.05 seconds = 34.72 MB/sec You may recognise the difference :) sdb is a stripped RAID array sdc is mirrored, but that does not really explain such poor performance there are 4 physical 10krpm drives sdc is each 8GB on drive1 and drive2 sdb has the rest of drive1, drive2 and complete drive3 and drive4 as one stripped array So the task is to get this fixed. Happy bidding and just ask for more info if you need more. Contact for feedback during project can be skype, msn, phone landline or mail. You may either specify a fixed price or the hourly charge. Please put in your comment which of those you is what you bid. (bids that don't include this info will be deleted) We need a invoice with a VAT ID -> no students and private bids (no invoice, no money)