|
Desktop |
Enterprise |
Operational Availability |
8 hours/day - 5 days/week |
24 hours/day - 7 days/week |
Work Load |
10 - 20% |
100% |
Performance |
Low - Moderate |
High |
Reliability |
Moderate:
- Outage affects only one user
- Critical data is not usually stored locally
- Higher Tolerance for long error recovery timeout
- Lower Mean Time Between Failure Acceptable
|
High:
- Outage affects multiple users
- Higher Mean Time Between Failure
- Intolerance for long Error Timeout
|
Robustness
Enterprise-class HDDs have higher tolerance internal parts - designed to meet the needs of high-availability environment, 24/7. Also, higher tolerance for vibration, heat, and the other environmental factors which comes in a server environment.
Performance
Enterprise-class drives generally incorporate internal mechanisms that allow faster data access
and retrieval. These features include heavier actuator magnets, faster spindle speeds, denser
magnetic media, and faster drive electronic components with more cache memory and faster
hard drive micro-processor speeds.
Sector Remapping
HDDs today have a built-in ability of repairing defective sectors with a backup supply of sectors. This repair process is seamless to the user. With a Desktop-class drive, the HDD will attempt to retrieve the data and remap the sector which is damaged, requiring as much time as several minutes. During this sector remapping process, a HDD can time out and become unresponsive to the HDD controller. Because of this, a HDD can be ejected from the controller, as the Controller believes that the HDD is defective as it is unresponsive.
To resolve this, sector remapping for Enterprise-class HDD is handled differently. On an Enterprise-class HDD, the HDD will attempt to retrieve the data from the affected sector, however if it cannot be retrieve under a few seconds, the HDD will mark the sector as defective and consider the data lost. The HDD maintains a lower time interval to perform sector remapping thus to avoid timing out or being ejected from the RAID Controller. This behavior is essential to maintain High Availability of the Volume, and to continue serving the data to customers and users.
After marking the sector defective, the HDD will then ask the controller to rebuild the missing data from the other Redundant drives (RAID 1, 5, 6 for example); the rebuilt data from the other drives will then be placed on a backup sector of the HDD.