#
339131 |
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03-Oct-2018 |
mav |
MFC r337191: MFV r337190: 9486 reduce memory used by device removal on fragmented pools
In the most fragmented real-world cases, this reduces memory used by the mapping from ~1GB to ~50MB of RAM per 1TB of storage removed. Less fragmented cases will typically also see around 50-100MB of RAM per 1TB of storage.
illumos/illumos-gate@cfd63e1b1bcf7ba4bf72f55ddbd87ce008d2986d
Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed by: Tim Chase <tim@chase2k.com> Approved by: Robert Mustacchi <rm@joyent.com> Author: Matthew Ahrens <mahrens@delphix.com>
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#
339106 |
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03-Oct-2018 |
mav |
MFC r336951: MFV r336950: 9290 device removal reduces redundancy of mirrors
Mirrors are supposed to provide redundancy in the face of whole-disk failure and silent damage (e.g. some data on disk is not right, but ZFS hasn't detected the whole device as being broken). However, the current device removal implementation bypasses some of the mirror's redundancy.
illumos/illumos-gate@3a4b1be953ee5601bab748afa07c26ed4996cde6
Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Prashanth Sreenivasa <pks@delphix.com> Reviewed by: Sara Hartse <sara.hartse@delphix.com> Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed by: Tim Chase <tim@chase2k.com> Approved by: Richard Lowe <richlowe@richlowe.net> Author: Matthew Ahrens <mahrens@delphix.com>
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#
332547 |
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16-Apr-2018 |
mav |
MFC r331701: MFV r331695, 331700: 9166 zfs storage pool checkpoint
illumos/illumos-gate@8671400134a11c848244896ca51a7db4d0f69da4
The idea of Storage Pool Checkpoint (aka zpool checkpoint) deals with exactly that. It can be thought of as a “pool-wide snapshot” (or a variation of extreme rewind that doesn’t corrupt your data). It remembers the entire state of the pool at the point that it was taken and the user can revert back to it later or discard it. Its generic use case is an administrator that is about to perform a set of destructive actions to ZFS as part of a critical procedure. She takes a checkpoint of the pool before performing the actions, then rewinds back to it if one of them fails or puts the pool into an unexpected state. Otherwise, she discards it. With the assumption that no one else is making modifications to ZFS, she basically wraps all these actions into a “high-level transaction”.
Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: John Kennedy <john.kennedy@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Approved by: Richard Lowe <richlowe@richlowe.net> Author: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com>
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#
332537 |
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16-Apr-2018 |
mav |
MFC r329802: MFV r329799, r329800: 9079 race condition in starting and ending condesing thread for indirect vdevs
illumos/illumos-gate@667ec66f1b4f491d5e839644e0912cad1c9e7122
The timeline of the race condition is the following: [1] Thread A is about to finish condesing the first vdev in spa_condense_indirect_thread(), so it calls the spa_condense_indirect_complete_sync() sync task which sets the spa_condensing_indirect field to NULL. Waiting for the sync task to finish, thread A sleeps until the txg is done. When this happens, thread A will acquire spa_async_lock and set spa_condense_thread to NULL. [2] While thread A waits for the txg to finish, thread B which is running spa_sync() checks whether it should condense the second vdev in vdev_indirect_should_condense() by checking the spa_condensing_indirect field which was set to NULL by spa_condense_indirect_thread() from thread A. So it goes on and tries to spawn a new condensing thread in spa_condense_indirect_start_sync() and the aforementioned assertions fails because thread A has not set spa_condense_thread to NULL (which is basically the last thing it does before returning).
The main issue here is that we rely on both spa_condensing_indirect and spa_condense_thread to signify whether a condensing thread is running. Ideally we would only use one throughout the codebase. In addition, for managing spa_condense_thread we currently use spa_async_lock which basically tights condensing to scrubing when it comes to pausing and resuming those actions during spa export.
Reviewed by: Matt Ahrens <mahrens@delphix.com> Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com> Approved by: Hans Rosenfeld <rosenfeld@grumpf.hope-2000.org> Author: Serapheim Dimitropoulos <serapheim@delphix.com>
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#
332525 |
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16-Apr-2018 |
mav |
MFC r329732: MFV r329502: 7614 zfs device evacuation/removal
illumos/illumos-gate@5cabbc6b49070407fb9610cfe73d4c0e0dea3e77
https://www.illumos.org/issues/7614: 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. Therefore, mirror and raidz devices can not be removed.
Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: John Kennedy <john.kennedy@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Richard Laager <rlaager@wiktel.com> Reviewed by: Tim Chase <tim@chase2k.com> Approved by: Garrett D'Amore <garrett@damore.org> Author: Prashanth Sreenivasa <pks@delphix.com>
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