Dell PowerVault MD3660i CLI Guide - Page 107
Cache Read Prefetch, Additional Information
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Parameter owner cacheReadPrefetch segmentSize usageHint enclosureLossProtect drawerLossProtect securityType Description NOTE: A space must be added between the last digit and the size (bytes, KB, MB, or GB) for values greater than 9. If you do not specify a capacity, all the available physical disk capacity in the disk group is used. If you do not specify the capacity unit, bytes is used as the default unit. The setting for which RAID controller module owns the disk group. Valid RAID controller module identifier values are 0 and 1. The identifier value is 0 for the RAID controller module on the top and 1 for the RAID controller module on the bottom when viewed from the rear of the enclosure. If you do not specify an owner, the RAID controller module firmware determines the owner. The setting to turn on or turn off cache read prefetch. To turn off cache read prefetch, set this parameter to FALSE. To turn on cache read prefetch, set this parameter to TRUE. The amount of data (in KB) that the RAID controller module writes on a single physical disk in a virtual disk before writing data on the next physical disk. Valid values are 8, 16, 32, 64, 128, 256, or 512. The setting for both the cacheReadPrefetch parameter and the segmentSize parameter to be default values. The default values are based on the typical I/O usage pattern of the application that is using the virtual disk. Valid values are fileSystem, dataBase, or multiMedia. The setting to enforce enclosure loss protection when you create the disk group. To enforce enclosure loss protection, set this parameter to TRUE. The default value is FALSE. The setting to enforce drawer loss protection when you create the disk group. To enforce drawer loss protection, set this parameter to TRUE. The default value is FALSE. The setting to specify the security level when creating the disk groups and all associated virtual disks. • none-The disk group and virtual disks are not secure. • capable-The disk group and virtual disks are capable of having security set, but security has not been enabled. • enabled-The disk group and virtual disks have security enabled. Additional Information Cache Read Prefetch The cacheReadPrefetch command lets the RAID controller module copy additional data blocks into cache while the RAID controller module reads and copies data blocks that are requested by the host from the physical disks 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 array that you use determine the number of additional data blocks that the RAID controller module reads into cache. Valid values for the cacheReadPrefetch parameter are TRUE or FALSE. 107
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