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| author | Mike Snitzer <snitzer@redhat.com> | 2012-03-28 19:41:28 +0200 |
|---|---|---|
| committer | Alasdair G Kergon <agk@redhat.com> | 2012-03-28 19:41:28 +0200 |
| commit | c4a69ecdb463a901b4645230613961e134e897cd (patch) | |
| tree | c53e0a569f3d390ea2a97f964225d5383c6401ec /Documentation/device-mapper | |
| parent | dm persistent data: remove space map ref_count entries if redundant (diff) | |
| download | linux-c4a69ecdb463a901b4645230613961e134e897cd.tar.xz linux-c4a69ecdb463a901b4645230613961e134e897cd.zip | |
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 <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'Documentation/device-mapper')
| -rw-r--r-- | Documentation/device-mapper/thin-provisioning.txt | 8 |
1 files changed, 5 insertions, 3 deletions
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 ---------------------- |