ZFS Tunables for Lustre Object Storage Servers (OSS)

When dirty data is less than 30% of, ZFS keeps one outstanding write per VDEV. Dirty data will build up very quickly, and because there is only one outstanding write per disk, ZFS will start to delay or even halt writes.

The  parameter should ideally match the backend storage capability. The code simply uses 10% of system memory as the default.

For a comprehensive description of all available ZFS and SPL module parameters, refer to the zfs-module-parameters(5) and spl-module-parameters(5) man pages.

In addition to the kernel module parameters, it is recommended that ZFS compression is also enabled when creating ZFS datasets for OSTs. Creating Lustre Object Storage Services (OSS) provides examples of the commands to create OSTs with compression enabled.