StorageClass parameters

Cache sizing, QoS, encryption and compression are all StorageClass parameters, which means they are chosen per class and fixed for the volumes that class creates. Running two profiles — a database class and an archive class, say — means two StorageClasses against the same pool.

Set them at install time with --set storageclass.<key>=..., or author a StorageClass of your own with the parameters in the middle column.

#Parameters

Helm value	Parameter	Default	Description
`config`	`config`	server default	Storage config profile name. Leave unset and the pool defaults it.
`labels`	`labels`	`storage=mgx`	Labels applied to the volume.
`minCacheRCacheSize`	`min_cache_r_cache_size`	`1024`	Read-cache floor, MiB.
`minCacheRWCacheSize`	`min_cache_rw_cache_size`	`1024`	Write-cache floor, MiB.
`maxCacheRCacheSize`	`max_cache_r_cache_size`	`20480`	Read-cache ceiling, MiB.
`maxCacheRWCacheSize`	`max_cache_rw_cache_size`	`3072`	Write-cache ceiling, MiB.
`ratioCacheRCacheSize`	`ratio_cache_r_cache_size`	`0.1`	Read cache as a ratio of volume size.
`ratioCacheRWCacheSize`	`ratio_cache_rw_cache_size`	`0.05`	Write cache as a ratio of volume size.
`qosRMBPerSec`	`qos_r_mbytes_per_sec`	unset	Read bandwidth cap, MB/s.
`qosWMBPerSec`	`qos_w_mbytes_per_sec`	unset	Write bandwidth cap, MB/s.
`qosRWMBPerSec`	`qos_rw_mbytes_per_sec`	unset	Combined read+write bandwidth cap, MB/s.
`qosRWIOPS`	`qos_rw_ios_per_sec`	unset	Combined read+write IOPS cap.
`storageEncryptSecret`	`storage_encrypt_secret`	unset	Name of the encryption secret. Unset means no encryption.
`storageCompress`	`storage_compress`	unset	Compression level, `0`–`9`.
`reclaimPolicy`	—	`Delete`	`Delete` or `Retain`.

Classes are created with volumeBindingMode: Immediate and allowVolumeExpansion: true.

A QoS or storage parameter left unset is omitted from the class entirely rather than sent as a zero, so the pool's own default applies.

#Cache sizing

The two cache sizes are computed at volume creation as

text

clamp(ratio * volume size in MiB, floor, ceiling)

which is why the ratio alone does not tell you the answer — see Caching for worked examples and for what to tune when a working set does not fit.

#A hand-written class

Everything above as YAML, for the case where you want a second profile rather than to change the chart's:

yaml

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: mgxcsi-sc-db
provisioner: csi.migrx.io
parameters:
  labels: "storage=mgx,profile=db"
  min_cache_r_cache_size: "4096"
  min_cache_rw_cache_size: "2048"
  max_cache_r_cache_size: "65536"
  max_cache_rw_cache_size: "8192"
  ratio_cache_r_cache_size: "0.2"
  ratio_cache_rw_cache_size: "0.1"
  qos_rw_ios_per_sec: "20000"
  storage_compress: "3"
reclaimPolicy: Retain
volumeBindingMode: Immediate
allowVolumeExpansion: true

Existing volumes keep the parameters they were created with; a class edit applies to volumes created after it.