SATA, PATA and SCSI : A Comparison

By soumitra, Gaea News Network
Wednesday, May 13, 2009

40mb-scsi-driveYes! The whole computer world is filled with gobbledygook terminologies. Even if I tell you that PATA stands for Parallel Advanced Technology Attachment, SATA means Serial Advanced Technology Attachment and SCSI is Small Computer System Interface, it will still be of little meaning to you. We have written a guide on SATA vs PATA and here is comparison between SATA, PATA drives and SCSI drives. In this comparison you will find :

ARTICLE CONTINUED BELOW

800px-ata_20070127_002

PATA Technology and features

It is an interface standard for the connection of sorage devices such as hard disks, SSDs and CD/DVD drives in computer. The standard used is basically AT Attachment Packet Interface or ATAPI standard. It evolved from the original IDE or Integrated Drive Electronics design. From the introduction of SATA in 2003 the use of PATA has declined in use since. It is still in use in many personal computers but seems to be obsolete in a few years. If you have PATA connectors like pictured below stock them now. The length of ATA is limited to only 18 inches and is only used as an internal computer storage interface.
800px-ata_on_mainboard

SATA Technology and Features

This is a wire replacement for the older ATA. The host adapters and devices communicate via a high speed serial cable. There are several advantages of SATA over PATA such as faster and more efficient data transfer and the ability to add or remove devices while operating which is known as hot swapping. The data cable of SATA has 7 conductors of which 2 lines is used for transmitting and two lines are used for receiving the three remaining pins serve as ground pins. They are more susceptible to accidental unplugging and breakage than PATA, but cables can be purchased that have a ‘locking’ feature, whereby a small (usually metal) spring holds the plug in the socket.

672px-sata_ports

SCSI Technology and Features

It is actually a set of standards for physically connecting and transferring data between computers and peripheral devices. The standard defines a set of protocols, commands for electrical and optical interfacing. Though it is most commonly used for hard disk and tape drives, other peripherals like scanners or CD drives can also be connected through it.
SCSI hides the complexity of physical format. Every device attaches to the SCSI bus in similar manner.
Upto 8 or 16 devices can be attached on a single bus. There can be any number of hosts and peripheral devices but at least one host is necessary.
SCSI uses handshaking signal between devices.
800px-scsi-1_gehaeuse

The Comparison

800px-scsi-terminator-exposed-hdr-0a

Speed

speed
Pic Source : techhead.co.uk
From the above picture you can see the difference of speeds of different technologies. On a general note it can be said that SCSI is faster than SATA with SATA II at 320 Mbps and normal SCSI operating at 320 Mbps.

Robustness

SCSI is a much robust interface. Almost every manufacturer provides longer warranty on SCSI. SATA drives are not less reliable either. But you should remember that a disk drive has a low failure rate because of increased quality of its head, platters and supporting manufacturing process, not because of certain interfaces.

Connectors

As SCSI has been around longer than IDE, there are more types of connectors and controllers available which can work together with appropriate adapters. There are only limited controllers available for SATA

Manufacturing Cost

SCSI costs much more than SATA or PATA. SATA connections are the cheapest to build.

Interfacing

SCSI interface can be used with control scanners, floppy drives, CD changers and tape drives other than interfacing the hard drives. SATA drives are primarily designed for transferring data between computer and mass storage device such as a hard disk and optical drives.

CPU Utilization

SCSI drives don’t use CPU power to run and leaves more CPU time for the rest of the system. SATA use processor to transfer data.

Compatibility

SCSI drives needs some knowledge to setup and SATA drives also has some problems. IDE drives are most compatible of all.

Hot Swapping

Serial SCSI offers hot swapping like SATA. PATA does not allow hot swapping.

Application

SCSI is mainly optimized for server and SATA are made for desktop applications. But now-a-days SATA drives are finding their way to the servers as they provide a cheaper option. For serious performance seekers 15k RPM SCSI drives are the best though a bit on the expensive side.

Conclusion

Thanks for reading this much long. From the above discussion, I think you have understood that SCSI are best suited for server application and SATA for desktops but SATA drives are becoming mature and perhaps will be a powerful alternative to SCSI. If you have anything in mind to suggest us, please feel free to do so.

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