Can I connect two other extra 6 GB/s data transfer rate supported INTERNAL HDDs

[vijay1700]

My motherboard is Intel DZ68PL and has only 2 on-board SATA ports that support 6GBPS data transfer rate, but I wanna connect 4 internal HDDs that support 6 GB/s data transfer rate together (All 4 HDDs at the same time). Is there any way to do this?

[Salmon Trout]

If your motherboard has a PCI-E slot you may be able to fit an extension card. This one has 4 SATA 3 connectors. You can get cards with more. For each drive you will need a data cable and a power cable. You may have to use SATA power splitter cables.

SATA III 4 Port PCI-e x1 Controller Card

[camerongray]

What sort of drives are you using, if we're just talking basic mechanical hard drives then chances are they won't be able to saturate even a 3Gb/s SATA II connection so you'd be able to use them with your board's SATA II ports without any performance degradation.  SATA II 3Gb/s can support up to 300MB/s of data throughput so worth either looking up performance benchmarks for your particular drives (or test them yourself with them hooked up to the SATA III ports), if they max out at less than 300MB/s then I'd just connect them to the motherboard's SATA II ports.