Looking to see what type of hard drive has the fastest transfer rate for new computer, thanks for your tips|||SCSI stands for "Small Computer System Interface", and is a standard interface and command set for transferring data between devices on both internal and external computer buses.
SCSI LogoSCSI is most commonly used for hard disks and tape storage devices, but also connects a wide range of other devices, including scanners, printers, CD-ROM drives, CD recorders, and DVD drives. In fact, the entire SCSI standard promotes device independence, which means that theoretically SCSI can be used with any type of computer hardware.
Since its standardization in 1986, SCSI has been commonly used in the Apple Macintosh and Sun Microsystems computer lines. It has never been popular in the IBM PC world, due to the lower cost and adequate performance of its ATA hard disk standard. The introduction of USB, FireWire, and ATAPI made SCSI a relatively unattractive proposition on PC due to its high cost and rising complexity.
At this time, SCSI is popular on high-performance workstations, servers, and high-end peripherals; and RAID arrays on servers almost always use SCSI hard disks. Desktop computers and notebooks more typically use the ATA/IDE or the newer SATA interfaces for hard disks, and USB or FireWire connections for external devices
Terms Bus Speed ( MB/sec)
SCSI-1 5
SCSI-2 10
SCSI-3 20
SCSI-3 20
SCSI-3 20
SCSI-3 UW 40
SCSI-3 UW 40
SCSI-3 UW 40
SCSI-3 U2 40
SCSI-3 U2 80
SCSI-3 U2W 80
SCSI-3 U2W 80
SCSI-3 U3 160
In addition, the fastest hard drives in the world use the SCSI interface. Best known are the Seagate Cheetahs, but IBM also offers SCSI drives at 10,000 rpm.
Serial ATA or SATA is the newest version of the ATA interface. SATA claims to support all the traditional ATA functions but does it over an interface cable with only 7 wires (instead of the normal 40 wires for traditional parallel ATA interfaces). SATA also claims it will be faster but the history of serial interfaces indicates you must be careful when reading such speed claims.
Discussing SATA is difficult because: a) SATA was created by a "secret society" that prohibits members from talking outside of their meetings, b) current SATA documents are available only to the members of the "secret society", c) by the time a SATA document is made public it is basically obsolete and has been replaced by a new but secret SATA document, d) the SATA "secret society" is working with the Serial Attached SCSI (SAS) committee(s) to also replace SCSI, e) the SATA documents that are public may be or will be re-published (probably with some changes?) by the T10 and T13 standards committees. All of this makes SATA a very confusing mess!SATA uses a 7 wire interface. Three of the wires are ground signals. The other 4 are two pairs of differential signals - one pair in each direction. SATA is using the transceiver technology used by Fiber (Fibre) Channel. Today's hardware runs at 1.5GHz and should be at 3GHz soon. ATA commands, status and data are transmitted in packets on this interface. This is done such that the traditional ATA command protocols are basically unchanged (more about this below).
How fast is SATA? Well... There are claims that it can transfer data up to 150Mbytes/second. Remember this is a burst data rate, not an average data rate. Parallel ATA using UltraDMA mode 6 (UltraDMA 133) claims it can transfer data up to 133Mbytes/second. Again this is a burst data rate and not an average data rate. Average data rates are probably less than 1/2 of these numbers, perhaps even as low as 1/3. Yes, SATA is in theory "faster" - but not by much.
SATA-1+ and SATA-2 (neither are part of ATA/ATAPI-7 at this time) include new data transfer and tagged command queuing schemes. It is unclear if these things will ever appear in future ATA/ATAPI-x standards. They may only appear in the SATA-2/SAS documents.
SATA supports a single device per SATA cable. A SATA cable can be longer than a parallel ATA cable (limited to 1.5 feet), perhaps up to 2 or 3 feet long.
Soon after completing the SATA-1 specification the SATA "secret society" continues working and have joined forces with the Serial Attached SCSI (SAS) sub-committee of T10 to merge SATA and SAS. The result so far is yet another version of SATA known as SATA-2. The end result is unclear. There are lots of poeple that would like to replace SCSI - remember 1394 was going to replace SCSI. It is fun to read some of the marketing hype: SATA and SAS have joined forces to "create the I/O interface that will solve every problem every known to exist in I/O interfaces". When have we heard this before?
Only time and questionable marketing practices will determine the outcome of this... Until the answer is known you should keep an eye on these two web sites:
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