From a561ddbec156c73ecf2852d77574ddef52970dcf Mon Sep 17 00:00:00 2001 From: Carlos Maiolino Date: Tue, 23 Jul 2013 11:03:16 -0300 Subject: dm thin: add data block size limits to Documentation Inform users that the data block size can't be any arbitrary number, i.e. its value must be between 64KB and 1GB. Also, it should be a multiple of 64KB. Signed-off-by: Carlos Maiolino Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon Acked-by: Joe Thornber --- Documentation/device-mapper/thin-provisioning.txt | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) (limited to 'Documentation/device-mapper') diff --git a/Documentation/device-mapper/thin-provisioning.txt b/Documentation/device-mapper/thin-provisioning.txt index 30b8b83bd33..50c44cf79b0 100644 --- a/Documentation/device-mapper/thin-provisioning.txt +++ b/Documentation/device-mapper/thin-provisioning.txt @@ -99,13 +99,14 @@ Using an existing pool device $data_block_size $low_water_mark" $data_block_size gives the smallest unit of disk space that can be -allocated at a time expressed in units of 512-byte sectors. People -primarily interested in thin provisioning may want to use a value such -as 1024 (512KB). People doing lots of snapshotting may want a smaller value -such as 128 (64KB). If you are not zeroing newly-allocated data, -a larger $data_block_size in the region of 256000 (128MB) is suggested. -$data_block_size must be the same for the lifetime of the -metadata device. +allocated at a time expressed in units of 512-byte sectors. +$data_block_size must be between 128 (64KB) and 2097152 (1GB) and a +multiple of 128 (64KB). $data_block_size cannot be changed after the +thin-pool is created. People primarily interested in thin provisioning +may want to use a value such as 1024 (512KB). People doing lots of +snapshotting may want a smaller value such as 128 (64KB). If you are +not zeroing newly-allocated data, a larger $data_block_size in the +region of 256000 (128MB) is suggested. $low_water_mark is expressed in blocks of size $data_block_size. If free space on the data device drops below this level then a dm event -- cgit v1.2.3-70-g09d2