diff options
| author | Joe Thornber <ejt@redhat.com> | 2012-07-27 15:08:16 +0100 |
|---|---|---|
| committer | Alasdair G Kergon <agk@redhat.com> | 2012-07-27 15:08:16 +0100 |
| commit | e49e582965b3694f07a106adc83ddb44aa4f0890 (patch) | |
| tree | fcc6ff02fd4bd9afa59b5fd3bdbb9991f1271d8a /Documentation/device-mapper | |
| parent | da105ed5fd7edcc5e0df7dbacef4dadda74e7ebe (diff) | |
dm thin: add read only and fail io modes
Add read-only and fail-io modes to thin provisioning.
If a transaction commit fails the pool's metadata device will transition
to "read-only" mode. If a commit fails once already in read-only mode
the transition to "fail-io" mode occurs.
Once in fail-io mode the pool and all associated thin devices will
report a status of "Fail".
Signed-off-by: Joe Thornber <ejt@redhat.com>
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 | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/Documentation/device-mapper/thin-provisioning.txt b/Documentation/device-mapper/thin-provisioning.txt index f5cfc62b7ad..30b8b83bd33 100644 --- a/Documentation/device-mapper/thin-provisioning.txt +++ b/Documentation/device-mapper/thin-provisioning.txt @@ -231,6 +231,9 @@ i) Constructor no_discard_passdown: Don't pass discards down to the underlying data device, but just remove the mapping. + read_only: Don't allow any changes to be made to the pool + metadata. + Data block size must be between 64KB (128 sectors) and 1GB (2097152 sectors) inclusive. @@ -239,7 +242,7 @@ ii) Status <transaction id> <used metadata blocks>/<total metadata blocks> <used data blocks>/<total data blocks> <held metadata root> - + [no_]discard_passdown ro|rw transaction id: A 64-bit number used by userspace to help synchronise with metadata @@ -257,6 +260,21 @@ ii) Status held root. This feature is not yet implemented so '-' is always returned. + discard_passdown|no_discard_passdown + Whether or not discards are actually being passed down to the + underlying device. When this is enabled when loading the table, + it can get disabled if the underlying device doesn't support it. + + ro|rw + If the pool encounters certain types of device failures it will + drop into a read-only metadata mode in which no changes to + the pool metadata (like allocating new blocks) are permitted. + + In serious cases where even a read-only mode is deemed unsafe + no further I/O will be permitted and the status will just + contain the string 'Fail'. The userspace recovery tools + should then be used. + iii) Messages create_thin <dev id> @@ -329,3 +347,7 @@ regain some space then send the 'trim' message to the pool. ii) Status <nr mapped sectors> <highest mapped sector> + + If the pool has encountered device errors and failed, the status + will just contain the string 'Fail'. The userspace recovery + tools should then be used. |