Enterprise-class versus Desktopclass Hard Drives Revision 1.
Enterprise-class versus Desktop-class Hard Drives Revision History Date April, 2008 Revision Number 1.0 Modifications Initial Release Disclaimers Information in this document is provided in connection with Intel® products. No license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted by this document.
Enterprise-class versus Desktop-class Hard Drives Introduction In today’s economic landscape server system integrators are challenged to balance data and system reliability with cost. It is important to balance the type, capacity, and number of hard drives in a system with the requirements of data integrity and availability.
Enterprise-class versus Desktop-class Hard Drives Enterprise versus Desktop Hard Drives Hard Drive Features To meet operational requirements, some vendors and drive models have significant differences in disk drive design for desktop class hard drives compared to enterprise class hard drives. This document examines these differences and describes how the drive design and feature set meet the needs of the two usage models.
Enterprise-class versus Desktop-class Hard Drives 1.1.4 Reliability Reliability is influenced by the factors described below. 1.1.4.1 Bad Sector Recovery Desktop drives perform heroic efforts to recover data in a bad sector. Usually there is one hard drive in a desktop system and a bad sector can result in a catastrophic failure of the operating system or an application failure. Typically desktop systems do not provide an online backup copy of the sector.
Enterprise-class versus Desktop-class Hard Drives Enterprise class drives provide a more sophisticated compensation for vibration by sensing the vibration motion of the drive, and by sensing head position and track alignment. The drive can then react with additional actuator strength or wait for the spindle motor to spin the target media location under the head again so that it can re-attempt access.
Enterprise-class versus Desktop-class Hard Drives Figure 1: RV Compensation Feedback Mechanisms Data * Typical Feedback Controller AF002543 No RV Compensation (Desktop-class drive) RV Sensors Data * Typical Feedback Controller AF002544 RV Compensation (Enterprise-class drive) Desktop class drives have less sophisticated mechanisms to compensate for vibration induced errors, which causes greater performance loss and a higher error rate.
Enterprise-class versus Desktop-class Hard Drives 1.1.4.5 Data Integrity One feature of an enterprise-class system is the implementation of “end-to-end” error detection. Transmitted data is accompanied by parity or checksum at every stage of transmission within the system. This allows data transmission errors to be detected, and in some cases corrected or retransmitted. Although desktop systems do have error detection in some subsystems, they do not usually provide this end-to-end data protection.
Enterprise-class versus Desktop-class Hard Drives 1.1.4.6 Variable Sector Size Many enterprise class hard drives (especially SCSI and SAS hard drives) have the ability to vary the sector size within limits. These drives utilize a 528 byte sector and allow the I/O controller (usually a RAID controller) to set the data portion of the sector to 512 bytes and to use the remaining sector capacity for a sector checksum.
Enterprise-class versus Desktop-class Hard Drives Drive Comparison Table Feature Performance Latency and Seek Time Command Queuing and Reordering Rotational Vibration Tolerance Typical I/Os per sec/drive (no RV) Typical I/Os per sec/drive (20 rad/sec/sec RV) Duplex Operation Customization FW Code Variable Sector Sizes LEDs Enterprise Desktop 5.
Enterprise-class versus Desktop-class Hard Drives Conclusion As hard drives technology changes, customers have a choice of products to use in their enterprise or desktop environment. It is important to properly balance the system requirements with hard drive features and choose a hard drive to meet usage requirements. Hard drive usage, reliability, and functionality can be optimized by choosing drives that meet the design specifications demanded by their target implementation.
Enterprise-class versus Desktop-class Hard Drives References Intel® Server and Intel® RAID products: http://www.intel.com/products/server/chassis/index.htm http://www.intel.com/products/server/storage/index.htm?iid=ncdcnav2+stor_sys http://www.intel.com/products/server/raid/index.htm?iid=serv_body+raid Enterprise-class hard drive vendors: http://www.fujitsu.com/global/services/computing/storage/hdd/ehdd/ 12 http://www.hgst.com/portal/site/en/menuitem.
