From 610325e5c2c10a8cb5837912278be9924df9bea1 Mon Sep 17 00:00:00 2001 From: Vladislav Bolkhovitin Date: Sat, 20 Aug 2016 01:33:47 +0000 Subject: [PATCH] scst README: add section about VMware and Ceph RBD space reclaim Reported-by: Alex Gorbachev git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@6961 d57e44dd-8a1f-0410-8b47-8ef2f437770f --- scst/README | 14 ++++++++++++++ scst/README_in-tree | 14 ++++++++++++++ 2 files changed, 28 insertions(+) diff --git a/scst/README b/scst/README index 41bc0576a..b2fff1aef 100644 --- a/scst/README +++ b/scst/README @@ -1952,6 +1952,20 @@ context switch is natural for such potentially long operation as EXTENDED COPY. +VMware and Ceph RBD space reclaim +--------------------------------- + +VMware with VMFS5 filesystem ignores UNMAP alignment, so if you use 4MB +Ceph RBD objects and VMFS5, only some discards will reclaim RBD space +due to 1MB discard not often hitting the tail of objects. + +Thus, to have efficient ESXi space reclamation with RBD and VMFS5, you are +recommended to use 1 MB object size in Ceph. + +See https://sourceforge.net/p/scst/mailman/message/35287598 thread for +details. + + Caching ------- diff --git a/scst/README_in-tree b/scst/README_in-tree index 78e94401d..65053019d 100644 --- a/scst/README_in-tree +++ b/scst/README_in-tree @@ -1805,6 +1805,20 @@ context switch is natural for such potentially long operation as EXTENDED COPY. +VMware and Ceph RBD space reclaim +--------------------------------- + +VMware with VMFS5 filesystem ignores UNMAP alignment, so if you use 4MB +Ceph RBD objects and VMFS5, only some discards will reclaim RBD space +due to 1MB discard not often hitting the tail of objects. + +Thus, to have efficient ESXi space reclamation with RBD and VMFS5, you are +recommended to use 1 MB object size in Ceph. + +See https://sourceforge.net/p/scst/mailman/message/35287598 thread for +details. + + Caching -------