In just about every traditional storage system, hardware failures might cause performance levels to degrade significantly. Practically speaking, this means application down-time. Such a reality is unacceptable in today's competitive global environment. The strong business requirement to keep applications up and running makes consistent performance paramount.
Nextra's revolutionary new architecture is designed for consistent performance. Its distributed rebuild approach and avoidance of cache write-through keep its high performance consistent through any hardware failure.
Distributed Rebuild and Reduced Overhead
Current methods for implementing storage redundancy involve mirrored pairs of disks or RAID-5 disk groups. Unfortunately, in most other systems, rebuild time takes between 6 and 25 hours, depending on disk size and protection scheme. The disk I/O-consuming rebuild process typically causes severe performance degradation until the rebuild is over.
Nextra's RAID-X protection scheme provides a distributed rebuild mechanism in which all disks participate in a given rebuild, with each disk rebuilding only a small portion. As a result, rebuild process overhead is minimal, and performance levels are unaffected. Rebuild time with Nextra is as little as 15 minutes for a 500 Gb drive.
No Write-through Mode
To achieve redundancy, all storage architectures must store written data in two cache units before the host is acknowledged. Yet, due to their architecture, most systems are unable to maintain cache redundancy upon failure of a cache unit or of the UPS system that maintains the cache data during power outages. These systems switch to "write-through" mode, acknowledging the host only after the write transaction has been committed to the disks. Unfortunately, write-through mode reduces the performance level during work so much as to be practically the equivalent of shutting down the system.
The Nextra system never uses write-through mode. Its flexible new architecture enables write requests to be cached in two different modules, even after module or UPS failure.
