RAID Lite Tower Add-On Cache
(Twenty Drive Configuration)

Today's high-performance CPUs push the limits of magnetic disk drives and RAID systems. RAID Lite overcomes limitations with a multi-policy caching scheme. The RAID Lite controller can currently be configured with 4, 8, 16 or 32MB of battery-backed SIMM-based read/write cache memory and can address up to 256MB (larger SIMMs will be available in the future). Cache memory is allocated by the controller memory management functions for Read Cache and Write Cache.

The following write cache policies are user-selectable for optimum performance within specific applications:

Write-Back Cache - A completion status is sent to the host operating system as soon as the cache (not the disk drive) receives the data to be written. The target SCSI drive will then receive the data at a more appropriate time in order to increase controller performance.

Write-Through Cache - Before a completion status is returned to the host operating system, data is written to the SCSI drive. This caching strategy is considered more secure, since a power failure will be less likely to cause loss of data. However, a Write-Through cache results in slightly lower performance in most environments.

The following read cache policies are user-selectable for optimum performance within specific applications:

Read Ahead Cache - This function improves data retrieval performance by allowing the controller to read in cache a full stripe of data at a time. This greatly improves the percentage of cache hits.

Super Read Ahead Cache - This function increases performance for applications that must access large blocks of sequential data. It incorporates intelligent data request monitoring to track data requested by the host. With Super Read Ahead enabled, the controller detects requests for data stored in sequence on the drives. It reads the data into cache so that cache remains at least one request ahead of the host.

Cache must be ordered separately for RAID Lite with a minimum order of 4MB. RAID Lite features a 72-pin SIMM slot with up to 32MB SIMMs available today. RAID Lite is configurable entirely as read cache or entirely as write cache.


RLT-Cache-4
One 4MB Cache Memory Card. ___________________________________________________________________
RLT-Cache-8
One 8MB Cache Memory Card. ___________________________________________________________________
RLT-Cache-16
One 16MB Cache Memory Card. ___________________________________________________________________
RLT-Cache-32
One 32MB Cache Memory Card. ___________________________________________________________________
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