Configurable ZFS Read and Write Throughput Limits

The Oracle Solaris 11.4 release provides the ability to limit a ZFS file system's reads and writes to disk. You can enable a read or write limit on a ZFS file system by setting the readlimit and writelimit properties, in units of bytes per second. Using these features allow you to optimize ZFS I/O resources in a multitenant environment.

The defaultwritelimit and defaultreadlimit properties are added to increase the manageability of a large number of ZFS file systems. If defaultwritelimit and defaultreadlimit properties are set, all file system descendants inherit the assigned value. If you apply the default read or write limit to ZFS file system, it is only applied to descendant file systems, and not to the file system itself. The read-only effectivereadlimit and effectivewritelimit properties are added to provide a view of what the effective limit is on a file system. The reported effective limit is the lowest data limit at any point between the parent and the indicated file system.

For example, you would set read and write limits as follows:

# zfs set writelimit=500mb rpool/apps/web
# zfs set readlimit=200mb rpool/apps/logdata

The following example shows how to display read and write limits:

# zfs get -r writelimit,readlimit rpool/apps
NAME                  PROPERTY    VALUE    SOURCE
rpool/apps            writelimit  default  default
rpool/apps            readlimit   default  default
rpool/apps/logdata    writelimit  default  default
rpool/apps/logdata    readlimit   200M     local
rpool/apps/web        writelimit  500M     local
rpool/apps/web        readlimit   default  default
rpool/apps/web/tier1  writelimit  default  default
rpool/apps/web/tier1  readlimit   default  default

You can display the effective write limit as follows:

# zfs get effectivewritelimit rpool/apps/web
NAME            PROPERTY             VALUE  SOURCE
rpool/apps/web  effectivewritelimit  500M   local

For more information, see Managing ZFS File Systems in Oracle Solaris 11.4.

Read the entire article on the upcoming features in Oracle Solaris 11.4 (PDF).