Where To Go After Configuring Das Cache In A Linux Server; Configuration Options For Ssds In Das Cache - Dell EMC VxFlex Ready Node 13G Manual

Preparing Disks

Where to go after configuring DAS Cache in a Linux server

Configuration options for SSDs in DAS Cache

Hardware Configuration and Operating System Installation Guide - Linux Servers
62
Example:
fscli --add-vol /dev/disk/by-id/
scsi-36141877069dec4001f22303a9dacfa83
Output similar to the following appears:
3. Repeat the previous step for every HDD device.
Results
All HDD devices are now added to the DAS Cache configuration. The HDD can be
accelerated later without causing VxFlex OS downtime.
DAS Cache configuration is required for any Linux-based node containing both HDDs
and SSDs, even if caching will not be used later on.
After configuring DAS Cache, the next step depends on whether you want to enable
caching or not.
If you do not want to enable caching, proceed with
server on page 65.
If you do want to enable caching, proceed with
Linux server on page 63.
DAS Cache supports one or two SSDs. To ensure best performance, any SSDs not
being used for DAS Cache should be added to a separate Storage Pool that is used
just for SSD devices.
In a configuration with two SSDs, creating an all-SSD storage pool for one of the
SSDs provides slightly better performance than dedicating both of the SSDs to DAS
cache. With an SSD storage pool, you are guaranteed good performance all the time,
whereas in a cached pool, the performance depends on the locality of the workload,
with poor locality resulting in HDD-like performance.
When adding cache, cache tags are assigned to all of the sections in the SSD cache
device.
DAS Cache starts to flush writes from the SSD to the HDDs when it reaches 60%
capacity. Because of data mirroring, cache capacity may need to be up to twice the
capacity of daily writes. To determine how many SSDs to allocate to DAS Cache to
make use of DAS Cache acceleration, the caching capacity per day is equal to:
(storage capacity of SSDs * number of SSDs allocated for caching *
number of nodes in the storage pool * 0.6)/2
If the system uses less than that amount of writes per day, all writes can be serviced
by cache.
Retrieve device paths in a Linux
Enabling DAS Cache acceleration in a