3Ware 720-0192-00 Manual

Also see for 3WARE 9650SE: User guide User guide Cli guide User guide addendum Specification

Contents

3Ware 720-0192-00 Manual Manual pdf 103 page image

Chapter 2. CLI Syntax Reference95 3ware SAS/SATA RAID Controller CLI Guide, Version 9.5.2Read Cache Basic Mode is used to store read cache data locally on thecontroller that has recently been written to media and is likely to be frequentlyaccessed. This improves read access times for applications such as a databasethat can take advantage of storage caching. The read cache may be disabledwithout reducing performance for applications that are write intensive, or thatrarely read back data recently written..Read Cache Intelligent Mode enables the Intelligent Read Prefectch (IRP)feature.The Intelligent Read Prefetch feature includes a typical read-ahead cachingmethod which is used to proactively retrieve data from media and store itlocally on the controller with the anticipation that it may be requested by thehost. For example, the host may read blocks 1, 2, and 3. With the read-aheadcaching included in IRP, the controller will also retrieve and hold in its cacheblocks 4, 5, and 6 in anticipation of getting those command requests from thehost. By loading a larger set of data into the cache, chances are improved thatanother request can be filled by data that is already in the cache. This can behelpful with applications that are sequential in nature, such as video ondemand, video surveillance playback, and restoring from a disk-to-diskbackup. Performance benefits of read-ahead are especially pronounced whenthe host queue depth is low. In addition, read-ahead caching also improvessequential read performance when the unit is degraded.The Intelligent Read Prefetch (IRP) feature also includes an adaptive streammanagement layer to improve performance at higher queue depths in multipleread only or mixed read/write stream environments. The performanceimprovements should be seen for most RAID types regardless of the unit’soperating unit state (normal, degraded, and so forth).Example://localhost> /c0/u0 set rdcache=basicSetting Read Cache Policy on /c0/u0 to [basic] ... Done./cx/ux set identify=on|offThis feature only applies to 9000 series SX/SE/SA model controllers.This feature requires a supported enclosure. For additional information aboutenclosure-related commands, see “Enclosure Object and ElementCommands” on page 123.This command allows you to identify a unit within an enclosure by blinkingthe LEDs associated with the drive slots of the specified unit.Example://localhost> /c0/u0 set identify=onSending Identify request for unit /c0/u0 to [on] ... Done.