Serverių kietasis diskas (HDD) HP 653950-001, 2.5"

Substitute HDD Qualification Procedure
When fulfilling a service spares order, customers may receive a hard disk drive that is different from their original. Substitute devices are necessary as older technology products reach end-of-life and are no longer available on the market. The HP HDDQ process consists of sophisticated, vigorous testing to ensure that disk drive substitutions are compatible with customers' systems. Customers enjoy peace of mind knowing that HP has developed and maintains one of the most disciplined and well-structured testing processes in the industry. With superior qualification and testing, HP is able to offer a three-year pre-failure warranty on HP SCSI hard disk drives (Must be running HP Insight Manager for Pre-Failure Warranty).

The differences between the original and substituted product may be in spin speed, capacity, interface, or all of these. HP addresses these factors with the procedures described below:

Spin Speed
The rotational speed of the disk, commonly referred to as 'rpm', has changed in recent years from 7200 to 10,000, and now to15,000 rpms. Increased spin speed results in reduced mechanical latency, which makes for a higher performing drive. A faster spin speed can also result in a drive that consumes more power and dissipates more heat. However, by reducing the rotating mass of the drive, these effects can be negated. As part of the HDD stringent qualification process, HP measures the power consumption of all drive types. Only drives with equal or lower power consumption characteristics relative to the original are allowed to be substituted into older applications.

Interface
Since 1981, there have been several generations of the SCSI protocol. Each new generation has doubled the performance of the previous one. SCSI performance has ranged from an 8-bit, single-ended (SE) interface transferring data up to 4 MB/s to the latest 16-bit, low-voltage differential (LVD) interface transferring data at 320 MB/s per channel. The drive communicates with the host controller across this interface, and much work has been done throughout the industry to retain backwards compatibility as new interfaces have been introduced. Although there have been many generations of SCSI, there are only three basic SCSI specifications: SCSI-1, SCSI-2, and SCSI-3.

Drives utilizing the newer interfaces can be substituted into older applications as long as the physical connections are compatible. The interface speed at which the drive and host controller operate at will be the slower of the two devices. Each drive on the bus negotiates independently with the host controller.

Capacity
Capacity is the disk drive parameter that has experienced the most growth. Steady increases in areal density have pushed the size of SCSI drives from 4.3GB to 146GB in less than ten years. The amount of data that can be put onto a single platter dictates the minimum capacity point for a given generation of product. Typically, substituting a higher capacity drive for a smaller capacity has no effect on the performance of an application. When a larger drive is introduced into an existing RAID set, the additional capacity above that of the existing set is unusable.

However, this has no effect on the operation. Smaller capacity drives can be artificially created by limiting the useable capacity of a drive through the firmware. Essentially, the firmware only allows a given amount of the total capacity to be accessed. HP employs this method in order to provide lower capacity drives after the native capacity units are no longer available. The HP qualification process includes testing of these drives to ensure continued compatibility in customer systems.

Summary
When hard disk drives age and reach end-of-life status, substitute drives are necessary. Spin speed, capacity, interface, or all of these factors are taken into account with HP HDDs. Customers will have peace of mind when employing HP HDD substitutes knowing that HP quality tests every hard disk drive before approving it for use. By purchasing HP disk drive products, the customer has bought into a tradition of excellence and commitment that consistently produces the highest quality at competitive price points, designed to fully integrate across the HP enterprise class line of servers and storage.