From: Steven Jenkins Date: Tue, 11 Mar 2008 17:54:42 +0000 (+0000) Subject: none X-Git-Url: http://git.openafs.org/?p=openafs-wiki.git;a=commitdiff_plain;h=3896917a15847ab8d077faab801df508a0cb3cce;hp=d7f9233aad8f727fc1bc77bb18bb93669a7426e7 none --- diff --git a/AFSLore/DemandAttach.mdwn b/AFSLore/DemandAttach.mdwn index 157c031..b66aa3d 100644 --- a/AFSLore/DemandAttach.mdwn +++ b/AFSLore/DemandAttach.mdwn @@ -13,18 +13,20 @@ The key engine for offlining volumes is the VLRU (Volume Least Recently Used) qu VLRU works in a manner similar to a generational garbage collector. There are five queues on which volumes can reside: 1. new -2. intermediate +2. mid 3. old 4. held: queue for volumes which are administratively barred from VLRU activity 5. candidate: queue for volumes which have not been accessed recently, and thus are canddidates for soft detachment -The new, intermediate, and old queues are generational queues for active volumes, with the state transitions among them controlled by the following inactivity rules: +The new, mid, and old queues are generational queues for active volumes, with the state transitions among them controlled by the following inactivity rules: - candidate->new activity present - new->candidate (1\*vlruthresh) minutes since last transition; no activity - new->mid (2\*vlruthresh) minutes since last transition; activity present - mid->old (4\*vlruthresh) minutes since last transition; activity present -- old->mid 92\*vlruthresh) minutes since last transition; no activity +- old->mid (2\*vlruthresh) minutes since last transition; no activity - mid->new (1\*vlruthresh) minutes since last transition; no activity +The idea is that as a volume is used, it gets pushed into a 'more used' generation (i.e., 'old' is 'more used' than 'mid', which is 'more used' than 'new'). this provides a weighting so that volumes which are used more will tend to be in the mid and old queues, not in the new or candidate queues, thus staying in online. + Note that the VLRU engine can be controlled and tuned by the vlrudisable, vlruthresh, vlruinterval, and vlrumax parameters to the fileserver.