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Types of Hard Disks

There are four types of Hard -Disks which are given below:-

1) SAS Serial Attached SCSI.
2) SCSI Small Computer Systems Interface.
3) SATA Serial ATA or Serial Advanced Technology Attachment.
4) IDE Integrated/Intelligent Drive/Device Electronics.

1) SAS Serial Attached SCSI:Serial Attached SCSI (SAS) carries SCSI forward to new generations of storage . It builds on 20-plus years of reliable SCSI technology with vast enhancements added over the years.This HDD’s quality, reliability and universal compatibility will more than meet the requirements of the future enterprise storage market. Due to its SCSI forbearers, it will benefit storage management, it reduces the risk of storage technology change and increase system interoperability, flexibility and scalability. SAS is point-to-point technology with expander architecture. This combination offers high performance and reliable solutions which are quickly and easily deployable in the market. Note that this is serial, not parallel, so the drives cannot be chained. SAS drives are typically nearly as fast as their SCSI counterparts with the added benefit of a serial bus.

2) SCSI Small Computer Systems Interface:SCSI (Small Computer System Interface) is a hard drive standard that has been around a long time.It is known for its reliability and high cost, SCSI is usually used only in servers or very high-end workstations. Most of the people believe that the days of traditional SCSI are numbered, however, as iSCSI, SAS, and FC drives become more common in the market. Like ATA, SCSI is a parallel standard, so you can chain multiple drives together. Herein lies its limitation, because the bus has to share its bandwidth with all the drives in the chain. They are still a good option for servers that don’t have a lot of hard drives as SCSI drives typically spin at either 10,000 or 15,000 RPMs and offer much higher transfer rates/seek times when compared to most other drive types. The current U320 standard allows a theoretical data transfer rate of 320 MB/s, though U640 drives are starting to hit the market as well.

3) SATA Serial ATA or Serial Advanced Technology Attachment:Serial ATA (SATA) has a solid, reliable position in the desktop industry going back to 2001 when SATA 1.0 specification was completed with a performance rate of 1.5Gb/s. Its heritage is ATA, which is firmly grounded in the internal desktop storage industry. SATA is positioned to go into the future as the serial successor to ATA, continuing on the desktop, entry-level server and entry-level networked storage systems. As a serial 110 technology, SATA is a point-to-point topology. It enables hot-plug devices, thinner and longer cables and cyclical redundancy checking (CRC) for enhanced data reliability. SATA is currently gaining enhancements from the specification called “Extensions to Serial ATA 1.0.” Definition of system-level device activity SATA command queuing, extended differential voltage ranges and LED behavior are included in the extensions.

4)IDE Integrated/Intelligent Drive/Device Electronics:IDE hard disks have been around from many years. Prior to these drives, hard disks were interfaced to a PC motherboard via an expansion board known as a hard disk controller. The drive did most of the mechanical stuff and performed basic electronic/servo functions; the controller told it in detail what to do. The development of the IDE hard moved most of the electronics and firmware (low-level software on a chip) from the controller to a printed circuit board on the drive itself. In the process, a buffer/cache’ memory was added to the electronics to speed-up the process of reading and writing hard disk drive data. The drive got “smarter.” Overall costs went down and performance went up.It the cheapest hard drive.