From c4a69ecdb463a901b4645230613961e134e897cd Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Wed, 28 Mar 2012 18:41:28 +0100 Subject: dm thin: relax hard limit on the maximum size of a metadata device The thin metadata format can only make use of a device that is <= THIN_METADATA_MAX_SECTORS (currently 15.9375 GB). Therefore, there is no practical benefit to using a larger device. However, it may be that other factors impose a certain granularity for the space that is allocated to a device (E.g. lvm2 can impose a coarse granularity through the use of large, >= 1 GB, physical extents). Rather than reject a larger metadata device, during thin-pool device construction, switch to allowing it but issue a warning if a device larger than THIN_METADATA_MAX_SECTORS_WARNING (16 GB) is provided. Any space over 15.9375 GB will not be used. Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon --- Documentation/device-mapper/thin-provisioning.txt | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'Documentation/device-mapper/thin-provisioning.txt') diff --git a/Documentation/device-mapper/thin-provisioning.txt b/Documentation/device-mapper/thin-provisioning.txt index da50347c0053..a119fbdd0604 100644 --- a/Documentation/device-mapper/thin-provisioning.txt +++ b/Documentation/device-mapper/thin-provisioning.txt @@ -75,10 +75,12 @@ less sharing than average you'll need a larger-than-average metadata device. As a guide, we suggest you calculate the number of bytes to use in the metadata device as 48 * $data_dev_size / $data_block_size but round it up -to 2MB if the answer is smaller. The largest size supported is 16GB. +to 2MB if the answer is smaller. If you're creating large numbers of +snapshots which are recording large amounts of change, you may find you +need to increase this. -If you're creating large numbers of snapshots which are recording large -amounts of change, you may need find you need to increase this. +The largest size supported is 16GB: If the device is larger, +a warning will be issued and the excess space will not be used. Reloading a pool table ---------------------- -- cgit v1.2.2