Features
Feature Flags Overview
See these slides (Jan 2012) for more details.
libzfs_core
See this blog post (Jan 2012) and associated slides and video for more details.
CLI Usability
These are improvements to the command line interface. While the end result is a generally more friendly user interface, getting the desired behavior often required modifications to the core of ZFS.
Listed in chronological order (oldest first).
Pool Comment
OpenZFS has a per-pool comment property which can be set with the zpool set command, but can be read even if the pool is not imported, so it is accessible even if the pool cannot be imported.
illumos | Nov 2011 |
FreeBSD | ?? |
ZFS on Linux | Aug 2012 |
Mac ZFS | ?? |
Size Estimates for zfs send and zfs destroy
This feature enhances OpenZFS's internal space accounting information. This new accounting information is used to provide a -n (dry-run) option for zfs send which can instantly calculate the amount of send stream data a specific zfs send command would generate. It is also used for a -n option for zfs destroy which can instantly calculate the amount of space that would be reclaimed by a specific zfs destroy command.
illumos | Nov 2011 |
FreeBSD | ?? |
ZFS on Linux | Jul 2012 |
Mac ZFS | ?? |
vdev Information in zpool list
OpenZFS adds a -v option to the zpool list command which shows detailed sizing information about the vdevs in the pool:
$ zpool list -v NAME SIZE ALLOC FREE EXPANDSZ CAP DEDUP HEALTH ALTROOT dcenter 5.24T 3.85T 1.39T - 73% 1.00x ONLINE - mirror 556G 469G 86.7G - c2t1d0 - - - - c2t0d0 - - - - mirror 556G 493G 63.0G - c2t3d0 - - - - c2t2d0 - - - - mirror 556G 493G 62.7G - c2t5d0 - - - - c2t4d0 - - - - mirror 556G 494G 62.5G - c2t8d0 - - - - c2t6d0 - - - - mirror 556G 494G 62.2G - c2t10d0 - - - - c2t9d0 - - - - mirror 556G 494G 61.9G - c2t12d0 - - - - c2t11d0 - - - - mirror 1016G 507G 509G - c1t1d0 - - - - c1t5d0 - - - - mirror 1016G 496G 520G - c1t3d0 - - - - c1t4d0 - - - -
illumos | Jan 2012 |
FreeBSD | ?? |
ZFS on Linux | Sept 2012 |
Mac ZFS | ?? |
ZFS list snapshot property alias
Functionally identical to Solaris 11 extension zfs list -t snap
.
illumos | not yet ported |
FreeBSD | ?? |
ZFS on Linux | Apr 2012 |
Mac ZFS | ?? |
ZFS snapshot alias
Functionally identical to Solaris 11 extension zfs snap
.
illumos | not yet ported |
FreeBSD | ?? |
ZFS on Linux | Apr 2012 |
Mac ZFS | ?? |
zfs send Progress Reporting
OpenZFS introduces a -v option to zfs send which reports per-second information on how much data has been sent, how long it has taken, and how much data remains to be sent.
illumos | May 2012 |
FreeBSD | ?? |
ZFS on Linux | Sept 2012 |
Mac ZFS | ?? |
Arbitrary Snapshot Arguments to zfs snapshot
illumos | Jun 2012 |
FreeBSD | ?? |
ZFS on Linux | August 2013 |
Mac ZFS | ?? |
Performance
These are significant performance improvements, often requiring substantial restructuring of the source code.
Listed in chronological order (oldest first).
SA based xattrs
Improves performance of linux-style (short) xattrs. (Not to be confused with Solaris-style Extended Attributes which are full-fledged files or "forks", like NTFS streams. This work could be extended to also improve the performance of small Extended Attributes whose permissions are the same as the containing file.)
Requires a disk format change and is off by default until Filesystem (ZPL) Feature Flags are implemented (not to be confused with zpool Feature Flags).
illumos | not yet |
FreeBSD | ?? |
ZFS on Linux | Oct 2011 |
Mac ZFS | ?? |
Note that SA based xattrs are no longer used on symlinks as of Aug 2013 until an issue is resolved.
Use the slog even with logbias=throughput
illumos | ?? |
FreeBSD | ?? |
ZFS on Linux | Oct 2011 |
Mac ZFS | ?? |
Asynchronous Filesystem and Volume Destruction
Destroying a filesystem requires traversing all of its data in order to return its used blocks to the pool's free list. Before this feature the filesystem was not fully removed until all blocks had been reclaimed. If the destroy operation was interrupted by a reboot or power outage the next attempt to import the pool (probably during boot) would need to complete the destroy operation synchronously, possibly delaying a boot for long periods of time.
With asynchronous destruction the filesystem's data is immediately moved to a "to be freed" list, allowing the destroy operation to complete without traversing any of the filesystem's data. A background process reclaims blocks from this "to be freed" list and is capable of resuming this process after reboots without slowing the pool import process.
The new freeing algorithm also has a significant performance improvement when destroying clones. The old algorithm took time proportional to the number of blocks referenced by the clone, even if most of those blocks could not be reclaimed because they were still referenced by the clone's origin. The new algorithm only takes time proportional to the number of blocks unique to the clone.
See this blog post for more detailed performance analysis.
illumos | May 2012 |
FreeBSD | ?? |
ZFS on Linux | Jan 2013 |
Mac ZFS | ?? |
empty bpobjs?
illumos | Aug 2012 |
FreeBSD | ?? |
ZFS on Linux | Dec 2012 |
Mac ZFS | ?? |
single copy arc
illumos | Sep 2012 |
FreeBSD | ?? |
ZFS on Linux | Dec 2012 |
Mac ZFS | ?? |
FASTWRITE Algorithm
Improves synchronous IO performance.
illumos | not yet ported |
FreeBSD | ?? |
ZFS on Linux | Oct 2012 |
Mac ZFS | ?? |
Note that a locking enhancement is being reviewed.
George's massive spacemap performance improvments (the set from 2012)?
also 16a4a8074274d2d7cc408589cf6359f4a378c861 and 9eb57f7f3fbb970d4b9b89dcd5ecf543fe2414d5
illumos | Nov 2012 |
FreeBSD | ?? |
ZFS on Linux | May 2013 |
Mac ZFS | ?? |
nop-write?
illumos | Nov 2012 |
FreeBSD | ?? |
ZFS on Linux | Not yet (as of Sept. 13, 2013) |
Mac ZFS | ?? |
lz4 compression
illumos | Jan 2013 |
FreeBSD | ?? |
ZFS on Linux | Jan 2013 |
Mac ZFS | ?? |
synctask rewrite
illumos | Feb 2013 |
FreeBSD | ?? |
ZFS on Linux | Sept 2013 |
Mac ZFS | ?? |
l2arc compression
illumos | Jun 2013 |
FreeBSD | ?? |
ZFS on Linux | Aug 2013 |
Mac ZFS | ?? |
arc shouldn't cache freed blocks
illumos | Jun 2013 |
FreeBSD | ?? |
ZFS on Linux | Jun 2013 |
Mac ZFS | ?? |
Improve N-way mirror performance
Queues read requests to least busy leaf vdev in mirrors.
illumos | not yet ported |
FreeBSD | ?? |
ZFS on Linux | Jul 2013 |
Mac ZFS | ?? |
smoother write throttle
The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() for more details.
The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c for more details.
illumos | Aug 2013 |
FreeBSD | not yet |
ZFS on Linux | not yet |
Mac ZFS | not yet |
Dataset Properties
These are new filesystem, volume, and snapshot properties which can be accessed with the zfs(1) command's get subcommand. See the zfs(1) manpage for your distribution for more details on each of these properties.
Property | Description | illumos | FreeBSD | ZFS on Linux | Mac ZFS |
---|---|---|---|---|---|
refcompressratio | The compression ratio acheived for all data referenced by (but not necessarily unique to) a snapshot, filesystem, or volume, expressed as a multiplier. | Jun 2011 | ?? | Aug 2012 | ?? |
clones | For snapshots, this property is a comma-separated list of filesystems or volumes which are clones of this snapshot. | Nov 2011 | ?? | Jul 2012 | ?? |
written | The amount of referenced space written to this dataset since the previous snapshot. | Nov 2011 | ?? | Jul 2012 | ?? |
written@<snap> | The amount of referenced space written to this dataset since the specified snapshot. This is the space referenced by this dataset, but not referenced by the specified snapshot. | Nov 2011 | ?? | Jul 2012 | ?? |
logicalused, logicalreferenced | The amount of space used or referenced, before taking into account compression. | Feb 2013 | ?? | not yet ported | ?? |