SATA 3 hard disk can be connected to SAS ports. But If i connect SATA 3 drive to a SAS port then can i get same speed as SATA 3 originally offers or will it be a difference? Will it reduce the performance than connecting to a SATA 3 port.
I have a intel server board which has more number of SAS ports and i have to connect my SATA 3 drives to these SAS ports.So i am concerned about the performance. So please help me on this
The first thing that should be noted is that for most practical workloads of a single mechanical disk, even SATA1 which offers a transfer rate of 150 MB/s would not present a bottleneck. The higher transfer rates are mainly relevant for either cached I/O or high-performance SSDs. The first case is rare enough not to make a significant difference in overall performance. The latter case is only a concern if your SSD actually is performing better than the link can handle even over a long term (SSD performance typically degrades as the disk fills up). So unless you are building a corner-case setup, you would not notice a performance difference, no matter the link speed.
Now the technical part: there are two SAS standards - the older SAS 1 with a data rate of 3 Gbps and the newer SAS2 with a data rate of 6 Gbps per link. Both include SATA compatibility. SAS1 controllers would negotiate SATA2 speeds (300 MB/s) with connected SATA devices. Most newer SAS2 controllers will negotiate SATA3 speeds (600 MB/s) with capable devices. You should simply consult your controller's documentation / spec sheet to see what it would support.
The best SATA 3 hard disks (the 10TB WD/HG) are around 275MB/s read speed. That's not even half of what SATA 3 supports.
There is no practical speed difference. The speed is dictated purely by the HDD performance.
This is valid for SSDs also. The fastest SATA SSDs today get close to the SATA limit (in theory) but do not exceed it.
