which one is better? SAS/FC/SATA/SCSI

depends on so many factors..
sas and fibre channel would typically give overall best performance.
but to truely compare - it will often depend on the type of data and quantity -
eg small files being written, large files being written, or lots of small reads, or large contiguous reads.
what sort of RAID you configure can also make a difference.
However in general - if you assume an identical physical drive with just a different controller interface then FC/SAS/SCSI/SATA would be my general order of performance.

Hoewever if you through cost effectiveness into the equation it is hard to beat a large SATA raid for performance vs cost

It is generally accepted that in the Enterprise, where you would expect to find a SAN, that the san uses SAS drives but is then connected on a FC connection to your server hosts.

A good SAN will have dual FC ports and DUAL NIC ports for crossover failure and redundancy.

Fibre Channel will always be quickest.
You can get some awesome performance out of JBOD's - but sacrifice the redundancy that you get from a SAN.
Don't forget to apply the normal ideas of performance - more spindles = quicker volumes

Hello ;

There's not that much difference between the drive technologies.

FC at 4Gbps is going to prove marginaly faster in the average SAN storage array than a 3.2Gbps SAS drive. So use more SAS drives in RAID-10 instead of your FC drives in RAID-5 and enjoy higher performance and lower cost.

Another point worth considering: how many spindles are on the bus or loop? Nine 15K RPM spindles on an Ultra320 SCSI bus won't out-perform nine 15K RPM 4Gb FC spindles, but they will outperform, say, two shelves worth of 15K RPM 4Gb FC spindles attached to the same FCAL. If those same FC drives are Dual-Ported, there will be an additional penalty in contention from two active storage processors.

If you're the typical shop (meaning, if you're implementing server virtualization because most of your servers aren't that I/O or CPU intensive), then you should probably concern yourself more with how much cache your SAN storage processor has and worry less about FC vs. U320.

in this link you can find a comparison between different drives technologies
http://www.webopedia.com/DidYouKnow/Computer_Science/2007/sas_sata.asp

Hope it helps you.
Regards.

Like Martin J Parker said:
for SCSI you can remove the equation, it's not supported any more.
there's a very interesting Technology used nowadays, iSCSI, it's Cheaper even Free with Microsoft Windows Server and it's included with new Storages.
Check this link Plz : http://searchstorage.techtarget.com/definition/iSCSI 

Let US know :)
Regards

iSCSI is NOT a drive technology it is a transfer protocol for presenting data storage to a device.

Well i think the Question is not only about Drives :)

I've seen iSCSI implemented over SAS and SATA - iSCSI refers to the SCSI command set passed over the IP network protocol and has little to do with the type of physical device connected. If you're looking at iSCSI I would still recommend SAS over SATA, although you can certainly get some cheap iSCSI SATA devices from Thecus.

Yes, if you want really fast look at SATA SSD.  Another option - if you can afford it - is to use a tiered approach which uses both SSD and SAS: http://www.infoworld.com/d/storage/infoworld-review-dell-iscsi-san-sizzles-ssd-dynamic-storage-tiering-625?page=0,0

SSD's are not reliable or large enough to provide a reliable storage medium as yet.

Fibre Channel you can get reliance on the networking side of it with dual fibre switches and opens up the possibilities of storage replication at an enterprise level.

16GB fibre channel is nearly here or Fibre channel over ethernet either way you#ll get some very fast kit

I think that's the whole point of the tiered approach - use smaller SSDs to get the speed, RAID it to improve reliability, fall-back to SAS RAID for the bulk of the storage, which will still be reasonably quick.  Check out that infoworld.com link above - it's interesting technology.

@Andy: yup, I already mentioned that. I think that we can consider both FC and SCSI as legacy drive interfaces. Everything going forward is SAS and SATA.

@AhmedHERMI:

Nowadays, most SAS drives are dual port, thus their speed has been increased to 6 Gb.

Not really; nowadays most SAS disks have two 6Gb ports, however not that many controllers use both ports and the second port is often reserved for a second controller for redundancy, especially when used in SAN attached storage.