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125 lines
3.3 KiB
ReStructuredText
125 lines
3.3 KiB
ReStructuredText
.. _mds-scrub:
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=====================
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Ceph Filesystem Scrub
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=====================
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CephFS provides the cluster admin (operator) to check consistency of a filesystem
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via a set of scrub commands. Scrub can be classified into two parts:
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#. Forward Scrub: In which the scrub operation starts at the root of the filesystem
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(or a sub directory) and looks at everything that can be touched in the hierarchy
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to ensure consistency.
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#. Backward Scrub: In which the scrub operation looks at every RADOS object in the
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filesystem pools and maps it back to the filesystem hierarchy.
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This document details commands to initiate and control forward scrub (referred as
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scrub thereafter).
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Initiate Filesystem Scrub
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=========================
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To start a scrub operation for a directory tree use the following command
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::
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ceph tell mds.a scrub start / recursive
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{
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"return_code": 0,
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"scrub_tag": "6f0d204c-6cfd-4300-9e02-73f382fd23c1",
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"mode": "asynchronous"
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}
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Recursive scrub is asynchronous (as hinted by `mode` in the output above). Scrub tag is
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a random string that can used to monitor the progress of the scrub operation (explained
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further in this document).
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Custom tag can also be specified when initiating the scrub operation. Custom tags get
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persisted in the metadata object for every inode in the filesystem tree that is being
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scrubbed.
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::
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ceph tell mds.a scrub start /a/b/c recursive tag0
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{
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"return_code": 0,
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"scrub_tag": "tag0",
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"mode": "asynchronous"
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}
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Monitor (ongoing) Filesystem Scrubs
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===================================
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Status of ongoing scrubs can be monitored using in `scrub status` command. This commands
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lists out ongoing scrubs (identified by the tag) along with the path and options used to
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initiate the scrub.
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::
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ceph tell mds.a scrub status
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{
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"status": "scrub active (85 inodes in the stack)",
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"scrubs": {
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"6f0d204c-6cfd-4300-9e02-73f382fd23c1": {
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"path": "/",
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"options": "recursive"
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}
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}
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}
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`status` shows the number of inodes that are scheduled to be scrubbed at any point in time,
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hence, can change on subsequent `scrub status` invocations.
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Control (ongoing) Filesystem Scrubs
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===================================
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- Pause: Pausing ongoing scrub operations results in no new or pending inodes being
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scrubbed after in-flight RADOS ops (for the inodes that are currently being scrubbed)
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finish.
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::
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ceph tell mds.a scrub pause
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{
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"return_code": 0
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}
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`scrub status` after pausing reflects the paused state. At this point, initiating new scrub
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operations (via `scrub start`) would just queue the inode for scrub.
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::
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ceph tell mds.a scrub status
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{
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"status": "PAUSED (66 inodes in the stack)",
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"scrubs": {
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"6f0d204c-6cfd-4300-9e02-73f382fd23c1": {
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"path": "/",
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"options": "recursive"
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}
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}
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}
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- Resume: Resuming kick starts a paused scrub operation.
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::
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ceph tell mds.a. scrub resume
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{
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"return_code": 0
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}
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- Abort: Aborting ongoing scrub operations removes pending inodes from the scrub
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queue (thereby aborting the scrub) after in-flight RADOS ops (for the inodes that
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are currently being scrubbed) finish.
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::
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ceph tell mds.a. scrub abort
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{
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"return_code": 0
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}
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