Configure and Customize Dell PowerFlex v3.6.x

Read RAM Cache settings for SDS

From version 2.x Read RAM Cache is disabled by default on the Storage Pool. Recommendation: Keep it disabled for SSD/Flash pools. For HDD pools, Read RAM Cache can help increase performance. If the node is storage only (in other words; is the node is only used for PowerFlex), then the recommendation is to turn on Read RAM Cache for HDD pools and use as much of the server DRAM as possible.

In a converged configuration (where PowerFlex is sharing the server with other applications), depending on the available DRAM resources, it may also help to turn on Read RAM Cache for HDD pools and increase the cache size from the default.

If users wish to enable/disable Read RAM Cache, perform either of the following steps. Read RAM Cache may be enabled/disabled on the Protection Domain, or for each SDS in the cluster.

Task	Command
To enable Read RAM cache	Run one of the following commands: scli --set_rmcache_usage --protection_domain_name <domain NAME> --storage_pool_name <pool NAME> --use_rmcache [--dont_use_rmcache] scli --enable_sds_rmcache [--disable_sds_rmcache] --sds_name <NAME> NOTE:Using this command would be required for every SDS in the cluster.
To increase the amount of Read RAM cache	Run the following command: scli --set_sds_rmcache_size ((--sds_id <ID> | --sds_name <NAME> | --sds_ip <IP> [--sds_port <PORT>]) | (--protection_domain_id <ID> | --protection_domain_name <NAME>)) --rmcache_size_mb <SIZE> [--i_am_sure] Where --rmcache_size_mb is the size of rmcache in MB, and the range is between 128MB-300GB. It is important to ensure that Read RAM cache is enabled at all levels (PD, SP, and SDS). When rmcache is properly enabled, query output will look like this: