HP ProLiant Servers AIS: Official Study Guide and Desk Reference

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6.5. SCSI Compared to Parallel ATA/IDE

SCSI hard drive technology has been the industry standard because of its reliability and superior protocol features. HP provides unique values for SCSI hard drive technology, such as the following:

  • Universal architecture

  • Optimized firmware

  • Superior testing and quality standards

Customers generally choose SCSI hard drive technology for its hot-plug capability in addition to higher data integrity, performance, and reliability.

ATA/IDE hard drive technology in server environments offers the lowest price per gigabyte and lowest power consumption per drive. It also provides the reliability needed in light-duty environments. ATA/IDE customers are looking for basic server functionality, such as static Web page delivery, entry-level file/print, or shared Internet access.

The following table lists the basic differences between parallel ATA and SCSI.

Attributes

Parallel ATA

SCSI

Performance

8ms seek times

5ms seek times

Spindle speed

Up to 7,200 rpm

Up to 15,000 rpm

Transfer rate

100MB/s

160MB/s (Ultra 3)

Scalability

2 drives per channel

15 drives per channel

Maximum cable length

19-inch parallel cable

20 ft

Reliability (mean time between failure, MTBF)

300 500K hours

1M hours

Ability of service

Non-hot-pluggable

Hot-pluggable

Manufacturers warranty

3-year

3-year

Design power on hours (5-year life span)

3,000h/year

8760h/year

Design operating temperature

35°C (95°F)

55°C (131°F)

Generations per year (average)

2

1

Queuing

Allows only one transaction at a time

Allows multiple, simultaneous transactions

Disconnect/reconnect

No; transaction ties up the bus until complete

Yes; bus disconnects after request and reconnects when the data is available

Serial ATA reduces the gap between the ATA and SCSI interfaces.

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