By default, the automatic extension is set to ‘100‘
# grep thin_pool_autoextend_threshold /etc/lvm/lvm.conf # Configuration option activation/thin_pool_autoextend_threshold. # thin_pool_autoextend_threshold = 70 thin_pool_autoextend_threshold = 100
These settings imply the function has been disabled. From the /etc/lvm/lvm.conf configuration file:
# how to handle automatic pool extension. The former defines when the
# pool should be extended: when its space usage exceeds this many
# percent. The latter defines how much extra space should be allocated for
# the pool, in percent of its current size.
# For example, if you set thin_pool_autoextend_threshold to 70 and
# thin_pool_autoextend_percent to 20, whenever a pool exceeds 70% usage,
# it will be extended by another 20%. For a 1G pool, using up 700M will
# trigger a resize to 1.2G. When the usage exceeds 840M, the pool will
# be extended to 1.44G, and so on.
# Setting thin_pool_autoextend_threshold to 100 disables automatic
# extensions. The minimum value is 50 (A setting below 50 will be treated
# as 50).
To enable the automatic extension, change both the ‘thin_pool_autoextend_percent‘ and ‘thin_pool_autoextend_threshold‘ settings:
thin_pool_autoextend_threshold = 70 thin_pool_autoextend_percent = 20
Which means whenever a pool exceeds 70% usage, it will be extended by another 20%. For a 1G pool, using 700M will trigger a resize to 1.2G. When the usage exceeds 840M, the pool will be extended to 1.44G, and so on.