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Wednesday, March 25, 2009

Recent Advancements and Future Challenges of Storage Systems

Recent Advancements and Future Challenges of Storage Systems
In the Internet environment, hard drives are becoming global storage devices that can access many types of data, manage and locate desired data, and securely preserve it wherever it resides.
By David H. C. Du, Fellow IEEE

Traditional goals of storage systems – performance, scalability, availability, and reliability

Other challenges – manageability, searching for the desired information, energy efficiency, long-term data preservation, and data security

The research on magnetic disks focuses on how to increase the aerial density and how to improve the reliability of the drive.

Another feature that has been included in today’s disk drives is a failure warning provided to the host systems when error rates exceed a threshold value. In 1994, a failure warning standard specification called self monitoring and reporting technology (SMART) was adopted by the disk drive industry.

On some disks like fiber channel (FC) drives, the processor can be programmed to execute XOR computations. By computing XOR on disks, it helps to reduce the need for such resources as CPU and redundant arrays of independent disk (RAID) controllers in parity computations.

The data available over the internet today is highly unstructured and heterogeneous. Therefore, the traditional way of accessing data via file name or url may not be adequate. As we are moving into the direction of accessing data based on their semantics, how to store semantic information with the data and how to allow data retrieval based on semantic become extremely challenging.

Intelligent storage devices – how we take advantage of the onboard computing and memory capability of a disk

DAS – direct attached storage
1. SCSI – small computer systems interface
2. ATA – advanced technology attachment (also known as IDE)
When multiple servers are required in an organization, DAS may seem to be low in cost from eeach server’s point of view. When the number of servers becomes larger, the DAS model becomes inefficient and expensive in the total cost of the ownership

NAS – Network attached storage
1. NFS – Network file system
2. CIFS – common internet file system

SAN – storage area network
Fiber channel and InfiniBand(IB) are two popular standards that provide physical connections and communication protocols in SAN. To a lesser extent, serial storage architecture (SSA) and gigabit (or 10 Gbit) Ethernet are also used for this purpose.
Supported topology – point to point, loop topology (FC-AL), and fabric
Supported topology – SSA string, SSA loop, and switched
Strong point – spatial reuse (multiple nonoverlapping simultaneous transfers on loop)
Limitations of SAN – distance and cost -> IP-based storage solutions
3 major IP storage standards – iSCSI, fiber channel over IP (FCIP), and iFCP
OSD – object-oriented storage device, intelligent storage device
Fault-tolerance storage – RAID

Additional challenges for current and future storage systems
Efficient power energy consumption – Massive array of idle disks (MAID), popular data concentration (PDC), Hibernator, dynamic revolutions per minute (DRPM)
Safe data protection – backup and efficient retrieval of keys, key recovery, long-term management, usability, scalability
Long-term data preservation

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