From a60e15d6b980c7c029c4c3da1f922a39ea24eac5 Mon Sep 17 00:00:00 2001 From: Allan Jude Date: Tue, 23 Jul 2024 20:51:01 +0000 Subject: [PATCH] Man page updates for dmu_ddt_copies Reviewed-by: Alexander Motin Reviewed-by: Brian Behlendorf Signed-off-by: Allan Jude Closes #15895 --- man/man4/zfs.4 | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/man/man4/zfs.4 b/man/man4/zfs.4 index aae3d7dfb5..0756418726 100644 --- a/man/man4/zfs.4 +++ b/man/man4/zfs.4 @@ -77,6 +77,17 @@ the array is dynamically sized based on total system memory. dnode slots allocated in a single operation as a power of 2. The default value minimizes lock contention for the bulk operation performed. . +.It Sy dmu_ddt_copies Ns = Ns Sy 3 Pq uint +Controls the number of copies stored for DeDup Table +.Pq DDT +objects. +Reducing the number of copies to 1 from the previous default of 3 +can reduce the write inflation caused by deduplication. +This assumes redundancy for this data is provided by the vdev layer. +If the DDT is damaged, space may be leaked +.Pq not freed +when the DDT can not report the correct reference count. +. .It Sy dmu_prefetch_max Ns = Ns Sy 134217728 Ns B Po 128 MiB Pc Pq uint Limit the amount we can prefetch with one call to this amount in bytes. This helps to limit the amount of memory that can be used by prefetching.