System information

Appendix
B-4
• Autonomous free space management
The free space on a disk group is managed as free chunks. A free chunk is created when an administrator deletes a logical
disk or shrinks its capacity. Free chunks are for creating new logical disks or for expanding a logical disk. By visualizing the
free space with easy management utilities, an administrator can easily manage the free space and avoid waste.
• Online de-fragmentation
To have a continuous free space for new logical disks, discontinuous free chunks on a disk group can be consolidated into
one big free chunk. This is accomplished by a background task to move the data on the disk group. Without the online de-
fragmentation, the administrator needs to manually move the data of logical disks, and unacceptable system downtime is
thus introduced.
• Online volume expansion and shrink
The capacity of a volume can be online expanded by adding the logical disks to the volume, which concatenates the space of
each logical disk to form a larger capacity. Because the expansion is done instantly without incurring any background tasks,
users can quickly start using the added capacity without waiting. Users can also reduce the capacity of a volume by removing
the concatenated logical disks. Freely expanding and shrinking a volume enables efficient storage resource management.
B.7 Adaptive Performance Optimization
The performance is one of the most important values of a storage system, because higher performance means the capability
to support larger organization, more transactions, and higher productivity. The RAID controller firmware fully utilizes the state-
of-art storage hardware technologies to deliver the best-of-breed performance. The administrator can further enhance the
performance by setting the extensive configurable performance parameters offered by the firmware and monitor the
performance regularly. The firmware also provides adaptive optimization algorithms that can intelligently self-monitor and
self-adjust the performance parameters.
• Adaptive read-ahead (pre-read, pre-fetch) optimization
Read-ahead operation improves the performance of sequential reads by pre-fetching data from disk drives according to
current hosts’ read commands. The firmware can further identify multiple sequential read streams in random access and
perform pre-read for the streams. The administrator can also specify the pre-read depth for dynamical tuning.
• Configurable write caching policies
Write cache can improve the response time and concurrency level of hosts’ write commands. With the write cache, the
controller can merge consecutive write commands to single write command and lower the disk drive’s utilization by avoiding
over-write commands. On the other hand, to ensure the best data reliability, the write policy can be set as write-through to
make sure all data is written to the disk media.
• Performance monitoring
The controller keeps extensive IO statistics for performance monitoring. The statistics include physical components, like host
ports and disk drives, as well as logical objects, like LUN, cache, and logical disks. The complete picture of the storage
performance profile is presented and performance tuning can be conducted more effectively.
• Intelligent IO processing
Intelligent IO processing algorithms are efficiently executed to optimize the command execution and streamline the data flow.
Disk IO scheduler is deployed to reduce the number of disk access and minimize the seek time among disk access.
Elaborated RAID algorithms are performed to minimize the number of parity update and shorten the response time. The
administrator is allowed to control these optimizations and tune the corresponding parameters.
• One-click performance optimization
To free the administrators from understanding those sophisticated performance parameters and tedious performance tuning,
the firmware provides predefined performance profiles for optimizing the storage system according to different workload.
Simply by one click on the GUI, a storage system optimized for time-critical, transaction-oriented, or high-throughput
applications can be built.