Compaq 3200 manual Using the Array Accelerator, Features

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Using the Array Accelerator

The Smart Array 3200 Controller 64-MB array accelerator provides 56-MB read/write cache, that improves data access performance to the drive array with the accelerator acting as a posted-write cache and as a read-ahead cache. The write cache can accept data from the server at a very high speed. At the same time, read and write caches can be accommodated by the drivers. The read- ahead cache uses a multi-threaded algorithm to predict the next likely read operation for the array. This data is then read into the array accelerator from the drives. When the Smart Array 3200 Controller receives a read request for the cached data, the data can be brought into the system at memory speeds and avoid the latency of a disk access. The array accelerator feature can be disabled manually with software or by the Automatic Performance Tuning Feature.

NOTE: The Smart Array 3200 Controller is not operable without the array accelerator board attached.

The array accelerator’s ECC memory provides a high level of data integrity. ECC memory detects and corrects hard and soft memory errors without affecting performance.

The array accelerator is backed up with onboard rechargeable batteries so that the data temporarily held (cached) there is safe during equipment failure or power outages. This is particularly important for data that has been cached by a posted-write, but has not yet been written to the hard drives. The batteries preserve data in the array accelerator for up to four days.

IMPORTANT: The rechargeable batteries on a new Smart Array 3200 Controller may be discharged when the board is first installed. During server power-up with discharged array accelerator batteries, Power-On Self-Test (POST) displays the code “1794,” indicating that the array accelerator is disabled. This does not require action on your part. The array accelerator is enabled automatically when the batteries are charged to 90 percent of their capacity.

It can take up to 36 hours for the internal circuitry to fully charge the batteries . During this time, the array accelerator will be disabled; the Smart Array 3200 Controller will function properly, but without the performance advantage of the array accelerator.