Dell PowerVault ME5 Series Storage System CLI Reference Guide

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cache-parameter

This basetype is used by show cache-parameters, when a volume is specified, to show volume cache properties.

Table 1. cache-parameter properties
Name	Type	Description
serial-number	string	If a volume is specified, its serial number.
volume-name	string	If a volume is specified, its name.
write-policy	string	If a volume is specified, its cache write policy. write-back: Write-back caching does not wait for data to be completely written to disk before signaling the host that the write is complete. This is the preferred setting for a fault-tolerant environment because it improves the performance of write operations and throughput. write-through: Write-through caching significantly impacts performance by waiting for data to be completely written to disk before signaling the host that the write is complete. Use this setting only when operating in an environment with low or no fault tolerance.
write-policy-numeric	uint32	Numeric equivalents for write-policy values. 0: write-through 1: write-back
cache-optimization	string	If a volume is specified, its cache optimization mode. standard: This controller cache mode of operation is optimized for sequential and random I/O and is the optimization of choice for most workloads. In this mode, the cache is kept coherent with the partner controller. This mode gives you high performance and high redundancy. standard-atomic-write: This controller cache mode includes the standard mode features but also guarantees that if a failure (such as I/O being aborted or a controller failure) interrupts a data transfer between a host and the storage system, the controller cache contains either all the old data or all the new data, not a mix of old and new data. This option has a slight performance cost because it maintains a secondary copy of data in cache so that if a data transfer is not completed, the old cache data can be restored. cache-hit-atomic-write: This controller cache mode includes the cache-hit mode features but also guarantees that if a failure (such as I/O being aborted or a controller failure) interrupts a data transfer between a host and the storage system, the controller cache contains either all the old data or all the new data, not a mix of old and new data. This option has a slight performance cost because it maintains a secondary copy of data in cache so that if a data transfer is not completed, the old cache data can be restored.
cache-optimization-numeric	uint32	Numeric equivalents for cache-optimization values. 0: standard 3: standard-atomic-write 5: cache-hit-atomic-write
read-ahead-size	string	The read-ahead cache setting of the volume. Disabled: Read-ahead is disabled. Adaptive: Adaptive read-ahead is enabled, which allows the controller to dynamically calculate the optimum read-ahead size for the current workload. Stripe: Read-ahead is set to one stripe. The controllers treat NRAID and RAID-1 disk groups internally as if they have a stripe size of 512 KB, even though they are not striped. 512 KB, 1 MB, 2 MB, 4 MB, 8 MB, 16 MB, or 32 MB: Size selected by a user.
read-ahead-numeric	uint32	Numeric equivalents for read-ahead-size values. -2: Stripe -1: Adaptive 0: Disabled 524288: 512 KB 1048576: 1 MB 2097152: 2 MB 4194304: 4 MB 8388608: 8 MB 16777216: 16 MB 33554432: 32 MB