zfs_arc_max_percent Parameter

Description

Determines the maximum size of the ZFS Adaptive Replacement Cache (ARC) as a percentage of total memory. See also user_reserve_hint_pct ZFS Parameter.

Data Type

Integer

Default

90% of total memory. ZFS only grows to the point where ZFS sees memory pressure from applications and from other kernel demands.

Range

Percentage from 0 to 100

Units

Percentage

Dynamic?

Yes

Validation

Yes, the range is validated.

When to Change

Setting zfs_arc_max_percent to 70% can help reduce disruptive events such as a large ARC reduction under memory pressure along with multi-second periods of no I/Os. Note that this smaller ARC might lead to additional cache misses and more IOPS requests to the storage devices. However, this result might be an acceptable price in exchange for the extra performance stability that a smaller ARC provides.

Commitment Level

Unstable