IBM System Storage DS3000 Programming Manual page 272

Cache Flush Modifier
Valid values for the cache flush modifier are listed in this table.
Value
Immediate
250
500
750
1
1500
2
5
10
20
60
120
300
1200
3600
Infinite
Cache Without Battery Enabled
Write caching without batteries enables write caching to continue if the controller batteries are completely
discharged, not fully charged, or not present. If you set this parameter to TRUE without an uninterruptible
power supply (UPS) or other backup power source, you can lose data if the power to the storage
subsystem fails. This parameter has no effect if write caching is disabled.
Modification Priority
Modification priority defines the amount of system resources that are used when modifying logical drive
properties. If you select the highest priority level, the logical drive modification uses the most system
resources, which decreases the performance for host data transfers.
Cache Read Prefetch
The cacheReadPrefetch parameter enables the controller to copy additional data blocks into cache while
the controller reads and copies data blocks that are requested by the host from the drive into cache. This
action increases the chance that a future request for data can be fulfilled from cache. Cache read prefetch
is important for multimedia applications that use sequential data transfers. The configuration settings for
the storage subsystem that you use determine the number of additional data blocks that the controller
reads into cache. Valid values for the cacheReadPrefetch parameter are TRUE or FALSE.
Segment Size
The size of a segment determines how many data blocks that the controller writes on a single drive in a
logical drive before writing data on the next drive. Each data block stores 512 bytes of data. A data block
3-226
IBM System Storage DS3000, DS4000, and DS5000: Command Line Interface and Script Commands Programming Guide
Description
Data is flushed as soon as it is placed into the cache.
Data is flushed after 250 ms.
Data is flushed after 500 ms.
Data is flushed after 750 ms.
Data is flushed after 1 s.
Data is flushed after 1500 ms.
Data is flushed after 2 s.
Data is flushed after 5 s.
Data is flushed after 10 s.
Data is flushed after 20 s.
Data is flushed after 60 s (1 min.).
Data is flushed after 120 s (2 min.).
Data is flushed after 300 s (5 min.).
Data is flushed after 1200 s (20 min.).
Data is flushed after 3600 s (1 hr).
Data in cache is not subject to any age or time
constraints. The data is flushed based on other criteria
that are managed by the controller.