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This might sounds stupid, but my hardware skills are not very strong.

I have a 2U box with MegaRAID SAS 9260-4i - RAID 5 (3 x 3TB SATA III 6Gbps )

using mega raid cli tool here is the drive info.

Device Speed: 6.0Gb/s. but Link Speed: 3.0Gb/s

Raw Size: 2.728 TB [0x15d50a3b0 Sectors]
Non Coerced Size: 2.728 TB [0x15d40a3b0 Sectors]
Coerced Size: 2.728 TB [0x15d400000 Sectors]
Emulated Drive: Yes
Firmware state: Online, Spun Up
Commissioned Spare : No
Emergency Spare : No
Device Firmware Level: CC47
Shield Counter: 0
Successful diagnostics completion on :  N/A
SAS Address(0): 0x5000ae40000168a8
Connected Port Number: 0(path0)
Inquiry Data:             Z1F0C8SHST3000DM001-9YN166                      CC47
FDE Capable: Not Capable
FDE Enable: Disable
Secured: Unsecured
Locked: Unlocked
Needs EKM Attention: No
Foreign State: None
Device Speed: 6.0Gb/s
Link Speed: 3.0Gb/s
Media Type: Hard Disk Device
Drive Temperature :24C (75.20 F)
PI Eligibility:  No
Drive is formatted for PI information:  No
Port-0 :
Port status: Active
Port's Linkspeed: 3.0Gb/s
Drive has flagged a S.M.A.R.T alert : No

I have updated the firmware on the card to the newest available firmware.

Not sure what Link speed means! can someone way in with more info?

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up vote 2 down vote accepted

The speeds are based on the SATA version supported by the components. SATA 2 is 3Gb/s and SATA 3 is 6Gb/s. The device speed refers to the actual storage device (the MegaRAID SAS in your case), while the link speed refers to the connectivity between the device and the system (i.e. motherboard/backplane/RAID/cables). Check what SATA version your motherboard supports, you'll probably find that it's SATA 2.

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I have checked the motherboard, TYAN S7012 (S7012GM4NR) and it is SATA 2, however the connection from my RAID card to drives is via single SAS cable connected to backplane, could the backplane be the issue? – user1007727 Feb 20 '13 at 17:25
It was the backplane! from my experience always by Dell! parts are cheap, and support is always available – user1007727 Jun 4 '13 at 18:09

This depends on your hardware... And the backplane...

You may have a server whose backplane is only 3G capable.

You may have disks who don't negotiate link properly...

What type of server is this (hopefully not SuperMicro)? What types of disks are these (make/model)?

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