OpenZFS 7614, 9064 - zfs device evacuation/removal

OpenZFS 7614 - zfs device evacuation/removal
OpenZFS 9064 - remove_mirror should wait for device removal to complete

This project allows top-level vdevs to be removed from the storage pool
with "zpool remove", reducing the total amount of storage in the pool.
This operation copies all allocated regions of the device to be removed
onto other devices, recording the mapping from old to new location.
After the removal is complete, read and free operations to the removed
(now "indirect") vdev must be remapped and performed at the new location
on disk.  The indirect mapping table is kept in memory whenever the pool
is loaded, so there is minimal performance overhead when doing operations
on the indirect vdev.

The size of the in-memory mapping table will be reduced when its entries
become "obsolete" because they are no longer used by any block pointers
in the pool.  An entry becomes obsolete when all the blocks that use
it are freed.  An entry can also become obsolete when all the snapshots
that reference it are deleted, and the block pointers that reference it
have been "remapped" in all filesystems/zvols (and clones).  Whenever an
indirect block is written, all the block pointers in it will be "remapped"
to their new (concrete) locations if possible.  This process can be
accelerated by using the "zfs remap" command to proactively rewrite all
indirect blocks that reference indirect (removed) vdevs.

Note that when a device is removed, we do not verify the checksum of
the data that is copied.  This makes the process much faster, but if it
were used on redundant vdevs (i.e. mirror or raidz vdevs), it would be
possible to copy the wrong data, when we have the correct data on e.g.
the other side of the mirror.

At the moment, only mirrors and simple top-level vdevs can be removed
and no removal is allowed if any of the top-level vdevs are raidz.

Porting Notes:

* Avoid zero-sized kmem_alloc() in vdev_compact_children().

    The device evacuation code adds a dependency that
    vdev_compact_children() be able to properly empty the vdev_child
    array by setting it to NULL and zeroing vdev_children.  Under Linux,
    kmem_alloc() and related functions return a sentinel pointer rather
    than NULL for zero-sized allocations.

* Remove comment regarding "mpt" driver where zfs_remove_max_segment
  is initialized to SPA_MAXBLOCKSIZE.

  Change zfs_condense_indirect_commit_entry_delay_ticks to
  zfs_condense_indirect_commit_entry_delay_ms for consistency with
  most other tunables in which delays are specified in ms.

* ZTS changes:

    Use set_tunable rather than mdb
    Use zpool sync as appropriate
    Use sync_pool instead of sync
    Kill jobs during test_removal_with_operation to allow unmount/export
    Don't add non-disk names such as "mirror" or "raidz" to $DISKS
    Use $TEST_BASE_DIR instead of /tmp
    Increase HZ from 100 to 1000 which is more common on Linux

    removal_multiple_indirection.ksh
        Reduce iterations in order to not time out on the code
        coverage builders.

    removal_resume_export:
        Functionally, the test case is correct but there exists a race
        where the kernel thread hasn't been fully started yet and is
        not visible.  Wait for up to 1 second for the removal thread
        to be started before giving up on it.  Also, increase the
        amount of data copied in order that the removal not finish
        before the export has a chance to fail.

* MMP compatibility, the concept of concrete versus non-concrete devices
  has slightly changed the semantics of vdev_writeable().  Update
  mmp_random_leaf_impl() accordingly.

* Updated dbuf_remap() to handle the org.zfsonlinux:large_dnode pool
  feature which is not supported by OpenZFS.

* Added support for new vdev removal tracepoints.

* Test cases removal_with_zdb and removal_condense_export have been
  intentionally disabled.  When run manually they pass as intended,
  but when running in the automated test environment they produce
  unreliable results on the latest Fedora release.

  They may work better once the upstream pool import refectoring is
  merged into ZoL at which point they will be re-enabled.

Authored by: Matthew Ahrens <[email protected]>
Reviewed-by: Alex Reece <[email protected]>
Reviewed-by: George Wilson <[email protected]>
Reviewed-by: John Kennedy <[email protected]>
Reviewed-by: Prakash Surya <[email protected]>
Reviewed by: Richard Laager <[email protected]>
Reviewed by: Tim Chase <[email protected]>
Reviewed by: Brian Behlendorf <[email protected]>
Approved by: Garrett D'Amore <[email protected]>
Ported-by: Tim Chase <[email protected]>
Signed-off-by: Tim Chase <[email protected]>

OpenZFS-issue: https://www.illumos.org/issues/7614
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/f539f1eb
Closes #6900

1 files changed, 59 insertions, 12 deletions

diff --git a/man/man8/zpool.8 b/man/man8/zpool.8
index 6480ca367..c0e8b24fe 100644
--- a/man/man8/zpool.8
+++ b/man/man8/zpool.8
@@ -20,7 +20,7 @@
 .\"
 .\"
 .\" Copyright (c) 2007, Sun Microsystems, Inc. All Rights Reserved.
-.\" Copyright (c) 2013 by Delphix. All rights reserved.
+.\" Copyright (c) 2012, 2017 by Delphix. All rights reserved.
 .\" Copyright (c) 2012 Cyril Plisko. All Rights Reserved.
 .\" Copyright (c) 2017 Datto Inc.
 .\" Copyright (c) 2017 George Melikov. All Rights Reserved.
@@ -144,8 +144,13 @@
 .Ar pool
 .Nm
 .Cm remove
+.Op Fl np
 .Ar pool Ar device Ns ...
 .Nm
+.Cm remove
+.Fl s
+.Ar pool
+.Nm
 .Cm replace
 .Op Fl f
 .Oo Fl o Ar property Ns = Ns Ar value Oc
@@ -438,8 +443,7 @@ section for an example of mirroring multiple log devices.
 Log devices can be added, replaced, attached, detached and removed.  In
 addition, log devices are imported and exported as part of the pool
 that contains them.
-Mirrored log devices can be removed by specifying the top-level mirror for the
-log.
+Mirrored devices can be removed by specifying the top-level mirror vdev.
 .Ss Cache Devices
 Devices can be added to a storage pool as
 .Qq cache devices .
@@ -1758,18 +1762,51 @@ result in partially resilvered devices unless a second scrub is performed.
 .It Xo
 .Nm
 .Cm remove
+.Op Fl np
 .Ar pool Ar device Ns ...
 .Xc
 Removes the specified device from the pool.
-This command currently only supports removing hot spares, cache, and log
-devices.
-A mirrored log device can be removed by specifying the top-level mirror for the
-log.
-Non-log devices that are part of a mirrored configuration can be removed using
+This command currently only supports removing hot spares, cache, log
+devices and mirrored top-level vdevs (mirror of leaf devices); but not raidz.
+.sp
+Removing a top-level vdev reduces the total amount of space in the storage pool.
+The specified device will be evacuated by copying all allocated space from it to
+the other devices in the pool.
+In this case, the
+.Nm zpool Cm remove
+command initiates the removal and returns, while the evacuation continues in
+the background.
+The removal progress can be monitored with
+.Nm zpool Cm status.
+This feature must be enabled to be used, see
+.Xr zpool-features 5
+.Pp
+A mirrored top-level device (log or data) can be removed by specifying the top-level mirror for the
+same.
+Non-log devices or data devices that are part of a mirrored configuration can be removed using
 the
 .Nm zpool Cm detach
 command.
-Non-redundant and raidz devices cannot be removed from a pool.
+.Bl -tag -width Ds
+.It Fl n
+Do not actually perform the removal ("no-op").
+Instead, print the estimated amount of memory that will be used by the
+mapping table after the removal completes.
+This is nonzero only for top-level vdevs.
+.El
+.Bl -tag -width Ds
+.It Fl p
+Used in conjunction with the
+.Fl n
+flag, displays numbers as parsable (exact) values.
+.El
+.It Xo
+.Nm
+.Cm remove
+.Fl s
+.Ar pool
+.Xc
+Stops and cancels an in-progress removal of a top-level vdev.
 .It Xo
 .Nm
 .Cm replace
@@ -2216,9 +2253,12 @@ option as follows:
 .Bd -literal
 # zpool iostat -v pool 5
 .Ed
-.It Sy Example 14 No Removing a Mirrored Log Device
-The following command removes the mirrored log device
-.Sy mirror-2 .
+.It Sy Example 14 No Removing a Mirrored top-level (Log or Data) Device
+The following commands remove the mirrored log device
+.Sy mirror-2
+and mirrored top-level data device
+.Sy mirror-1 .
+.Pp
 Given this configuration:
 .Bd -literal
   pool: tank
@@ -2246,6 +2286,13 @@ is:
 .Bd -literal
 # zpool remove tank mirror-2
 .Ed
+.Pp
+The command to remove the mirrored data
+.Sy mirror-1
+is:
+.Bd -literal
+# zpool remove tank mirror-1
+.Ed
 .It Sy Example 15 No Displaying expanded space on a device
 The following command displays the detailed information for the pool
 .Em data .