maxautogrow attributes determine how the VxVM cache daemon (
vxcached) maintains the cache if the
autogrow feature has been enabled and
vxcached is running:
highwatermark(default value is 90 percent),
vxcachedgrows the size of the cache volume by the value of
autogrowby(default value is 20% of the size of the cache volume in blocks). The new required cache size cannot exceed the value of
maxautogrow(default value is twice the size of the cache volume in blocks).
vxcacheddeletes the oldest snapshot in the cache. If there are several snapshots with the same age, the largest of these is deleted.
autogrow feature has been disabled:
vxcacheddeletes the oldest snapshot in the cache. If there are several snapshots with the same age, the largest of these is deleted. If there is only a single snapshot, this snapshot is detached and marked as invalid.
If the cache space becomes exhausted, the snapshot is detached and marked as invalid. If this happens, the snapshot is unrecoverable and must be removed. Enabling the
autogrow feature on the cache helps to avoid this situation occurring. However, for very small caches (of the order of a few megabytes), it is possible for the cache to become exhausted before the system has time to respond and grow the cache. In such cases, you can increase the size of the cache manually.
See "Growing and shrinking a cache" on page 354.
Alternatively, you can use the
set command to reduce the value of
highwatermark as shown in this example:
vxcache -g mydg set highwatermark=60 cobjmydg
You can use the
maxautogrow attribute to limit the maximum size to which a cache can grow. To estimate this size, consider how much the contents of each source volume are likely to change between snapshot refreshes, and allow some additional space for contingency.
If necessary, you can use the
set command to change other
autogrow attribute values for a cache.
vxcache(1M) manual page.
autogrowattributes are configured correctly for your needs.