Squid configuration directive store_dir_select_algorithm

Available in: 4   3.5   3.4   3.3   3.2   2.7   3.1   3.0   2.6  

For older versions than 3.3 see the linked pages above

Configuration Details:

Option Name:store_dir_select_algorithm
Default Value:store_dir_select_algorithm least-load
Suggested Config:

	How Squid selects which cache_dir to use when the response
	object will fit into more than one.

	Regardless of which algorithm is used the cache_dir min-size
	and max-size parameters are obeyed. As such they can affect
	the selection algorithm by limiting the set of considered



	This algorithm is suited to caches with similar cache_dir
	sizes and disk speeds.

	The disk with the least I/O pending is selected.
	When there are multiple disks with the same I/O load ranking
	the cache_dir with most available capacity is selected.

	When a mix of cache_dir sizes are configured the faster disks
	have a naturally lower I/O loading and larger disks have more
	capacity. So space used to store objects and data throughput
	may be very unbalanced towards larger disks.


	This algorithm is suited to caches with unequal cache_dir
	disk sizes.

	Each cache_dir is selected in a rotation. The next suitable
	cache_dir is used.

	Available cache_dir capacity is only considered in relation
	to whether the object will fit and meets the min-size and
	max-size parameters.

	Disk I/O loading is only considered to prevent overload on slow
	disks. This algorithm does not spread objects by size, so any
	I/O loading per-disk may appear very unbalanced and volatile.

	If several cache_dirs use similar min-size, max-size, or other
	limits to to reject certain responses, then do not group such
	cache_dir lines together, to avoid round-robin selection bias
	towards the first cache_dir after the group. Instead, interleave
	cache_dir lines from different groups. For example:

		store_dir_select_algorithm round-robin
		cache_dir rock /hdd1 ... min-size=100000
		cache_dir rock /ssd1 ... max-size=99999
		cache_dir rock /hdd2 ... min-size=100000
		cache_dir rock /ssd2 ... max-size=99999
		cache_dir rock /hdd3 ... min-size=100000
		cache_dir rock /ssd3 ... max-size=99999








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