A VAST Cluster can be configured to increase the amount of write buffers available to handle bursts of high bandwidth writes. This can increase the overall write speed during the burst. The write buffer capacity is dynamically increased by using flash drives for write buffers.
By default, the feature is enabled for VAST Clusters v5.2 and later.
The following limitation applies:
Use of flash write buffers on an EBox with the DBox HA capability enabled requires at least 10 boxes to be present on the cluster.
Benefits and Impact of Using Write Buffers on Flash
Using flash drives to store write buffers can improve the overall write speed for the cluster, especially during bursts for high bandwidth write operations such as, for example, AI checkpointing operations during model training. The improvement can be around 2-2.5X.
The implementation of this feature on a VAST Cluster allows up to a certain proportion of space on flash drives to be allocated for write buffers, if the over use of flash storage remains below a threshold level. Allocation of write buffer stripes on flash storage is done gradually, according to need, up to the limit.
Enabling or Disabling the Use of Write Buffers on Flash from the VAST CLI
Run this
cluster modifycommand to enable the use of write buffers on flash.vcli: admin> cluster modify --enable-use-flash-write-buffers
Run this command to disable the use of write buffers on flash.
vcli: admin> cluster modify --disable-use-flash-write-buffers
When disabled, any allocated write buffers on flash are flushed and the allocated space is returned.