Dell PowerFlex 4.6.x Install and Upgrade Guide

Fine granularity metadata cache

Fine granularity MD_Cache helps improve the performance of the system when using the fine granularity layout.

Fine granularity MD_Cache allocates a small portion of system memory to each SDS in the protection domain, for caching the metadata. The following formula below shows the amount of memory needed for fine granularity MD_Cache per SDS:

FGMC_RAM_in_GiB=(Total_Drive_Capacity_in_TiB/2)*4%*Compression_Factor*Percent_of_Metadata_to_Cache 

It is recommended to allocate 2 for compression factor and 2% for metadata to cache. Use the sizer tool to assess the amount of memory to allocate for metadata to cache. The maximum amount of memory that can be allocated per SDS is 32 GiB.

1. Run the following command to allocate the memory used by fine granularity MD_Cache on each SDS in the protection domain.

   scli --set_default_fgl_metadata_cache_size (--protection_domain_id <ID> | --protection_domain_name <NAME>) --metadata_cache_size_mb <SIZE>

2. Run the following command to enable fine granularity MD_Cache:

   scli --enable_fgl_metadata_cache (--protection_domain_id <ID> | --protection_domain_name <NAME>)

3. Run the following command to disable fine granularity MD_Cache:

   scli --disable_fgl_metadata_cache (--protection_domain_id <ID> | --protection_domain_name <NAME>)