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.Dd May 26, 2021
.Dt ZFS-EVENTS 5
.Os
.
.Sh NAME
.Nm zfs-events
.Nd Events created by the ZFS filesystem
.Sh DESCRIPTION
Description of the different events generated by the ZFS stack.
.Pp
Most of these don't have any description.
The events generated by ZFS have never been publicly documented.
What is here is intended as a starting point to provide documentation
for all possible events.
.Pp
To view all events created since the loading of the ZFS infrastructure
(i.e, "the module"), run
.Dl Nm zpool Cm events
to get a short list, and
.Dl Nm zpool Cm events Fl v
to get a full detail of the events and what information
is available about it.
.Pp
This manual page lists the different subclasses that are issued
in the case of an event.
The full event name would be
.Sy ereport.fs.zfs.\& Ns Em SUBCLASS ,
but we only list the last part here.
.
.Sh EVENTS (SUBCLASS)
.Bl -tag -compact -width "vdev.bad_guid_sum"
.It Sy checksum
Issued when a checksum error has been detected.
.It Sy io
Issued when there is an I/O error in a vdev in the pool.
.It Sy data
Issued when there have been data errors in the pool.
.It Sy deadman
Issued when an I/O request is determined to be "hung", this can be caused
by lost completion events due to flaky hardware or drivers.
See
.Sy zfs_deadman_failmode
in
.Xr zfs-module-parameters 5
for additional information regarding "hung" I/O detection and configuration.
.It Sy delay
Issued when a completed I/O request exceeds the maximum allowed time
specified by the
.Sy zio_slow_io_ms
module parameter.
This can be an indicator of problems with the underlying storage device.
The number of delay events is ratelimited by the
.Sy zfs_slow_io_events_per_second
module parameter.
.It Sy config
Issued every time a vdev change have been done to the pool.
.It Sy zpool
Issued when a pool cannot be imported.
.It Sy zpool.destroy
Issued when a pool is destroyed.
.It Sy zpool.export
Issued when a pool is exported.
.It Sy zpool.import
Issued when a pool is imported.
.It Sy zpool.reguid
Issued when a REGUID (new unique identifier for the pool have been regenerated) have been detected.
.It Sy vdev.unknown
Issued when the vdev is unknown.
Such as trying to clear device errors on a vdev that have failed/been kicked
from the system/pool and is no longer available.
.It Sy vdev.open_failed
Issued when a vdev could not be opened (because it didn't exist for example).
.It Sy vdev.corrupt_data
Issued when corrupt data have been detected on a vdev.
.It Sy vdev.no_replicas
Issued when there are no more replicas to sustain the pool.
This would lead to the pool being
.Em DEGRADED .
.It Sy vdev.bad_guid_sum
Issued when a missing device in the pool have been detected.
.It Sy vdev.too_small
Issued when the system (kernel) have removed a device, and ZFS
notices that the device isn't there any more.
This is usually followed by a
.Sy probe_failure
event.
.It Sy vdev.bad_label
Issued when the label is OK but invalid.
.It Sy vdev.bad_ashift
Issued when the ashift alignment requirement has increased.
.It Sy vdev.remove
Issued when a vdev is detached from a mirror (or a spare detached from a
vdev where it have been used to replace a failed drive - only works if
the original drive have been readded).
.It Sy vdev.clear
Issued when clearing device errors in a pool.
Such as running
.Nm zpool Cm clear
on a device in the pool.
.It Sy vdev.check
Issued when a check to see if a given vdev could be opened is started.
.It Sy vdev.spare
Issued when a spare have kicked in to replace a failed device.
.It Sy vdev.autoexpand
Issued when a vdev can be automatically expanded.
.It Sy io_failure
Issued when there is an I/O failure in a vdev in the pool.
.It Sy probe_failure
Issued when a probe fails on a vdev.
This would occur if a vdev
have been kicked from the system outside of ZFS (such as the kernel
have removed the device).
.It Sy log_replay
Issued when the intent log cannot be replayed.
The can occur in the case of a missing or damaged log device.
.It Sy resilver.start
Issued when a resilver is started.
.It Sy resilver.finish
Issued when the running resilver have finished.
.It Sy scrub.start
Issued when a scrub is started on a pool.
.It Sy scrub.finish
Issued when a pool has finished scrubbing.
.It Sy scrub.abort
Issued when a scrub is aborted on a pool.
.It Sy scrub.resume
Issued when a scrub is resumed on a pool.
.It Sy scrub.paused
Issued when a scrub is paused on a pool.
.It Sy bootfs.vdev.attach
.El
.
.Sh PAYLOADS
This is the payload (data, information) that accompanies an
event.
.Pp
For
.Xr zed 8 ,
these are set to uppercase and prefixed with
.Sy ZEVENT_ .
.Bl -tag -compact -width "vdev_cksum_errors"
.It Sy pool
Pool name.
.It Sy pool_failmode
Failmode -
.Sy wait ,
.Sy continue ,
or
.Sy panic .
See the
.Sy failmode
property in
.Xr zpoolprops 8
for more information.
.It Sy pool_guid
The GUID of the pool.
.It Sy pool_context
The load state for the pool (0=none, 1=open, 2=import, 3=tryimport, 4=recover
5=error).
.It Sy vdev_guid
The GUID of the vdev in question (the vdev failing or operated upon with
.Nm zpool Cm clear ,
etc.).
.It Sy vdev_type
Type of vdev -
.Sy disk ,
.Sy file ,
.Sy mirror ,
etc.
See the
.Sy Virtual Devices
section of
.Xr zpoolconcepts 8
for more information on possible values.
.It Sy vdev_path
Full path of the vdev, including any
.Em -partX .
.It Sy vdev_devid
ID of vdev (if any).
.It Sy vdev_fru
Physical FRU location.
.It Sy vdev_state
State of vdev (0=uninitialized, 1=closed, 2=offline, 3=removed, 4=failed to open, 5=faulted, 6=degraded, 7=healthy).
.It Sy vdev_ashift
The ashift value of the vdev.
.It Sy vdev_complete_ts
The time the last I/O request completed for the specified vdev.
.It Sy vdev_delta_ts
The time since the last I/O request completed for the specified vdev.
.It Sy vdev_spare_paths
List of spares, including full path and any
.Em -partX .
.It Sy vdev_spare_guids
GUID(s) of spares.
.It Sy vdev_read_errors
How many read errors that have been detected on the vdev.
.It Sy vdev_write_errors
How many write errors that have been detected on the vdev.
.It Sy vdev_cksum_errors
How many checksum errors that have been detected on the vdev.
.It Sy parent_guid
GUID of the vdev parent.
.It Sy parent_type
Type of parent.
See
.Sy vdev_type .
.It Sy parent_path
Path of the vdev parent (if any).
.It Sy parent_devid
ID of the vdev parent (if any).
.It Sy zio_objset
The object set number for a given I/O request.
.It Sy zio_object
The object number for a given I/O request.
.It Sy zio_level
The indirect level for the block.
Level 0 is the lowest level and includes data blocks.
Values > 0 indicate metadata blocks at the appropriate level.
.It Sy zio_blkid
The block ID for a given I/O request.
.It Sy zio_err
The error number for a failure when handling a given I/O request,
compatible with
.Xr errno 3
with the value of
.Sy EBADE
used to indicate a ZFS checksum error.
.It Sy zio_offset
The offset in bytes of where to write the I/O request for the specified vdev.
.It Sy zio_size
The size in bytes of the I/O request.
.It Sy zio_flags
The current flags describing how the I/O request should be handled.
See the
.Sy I/O FLAGS
section for the full list of I/O flags.
.It Sy zio_stage
The current stage of the I/O in the pipeline.
See the
.Sy I/O STAGES
section for a full list of all the I/O stages.
.It Sy zio_pipeline
The valid pipeline stages for the I/O.
See the
.Sy I/O STAGES
section for a full list of all the I/O stages.
.It Sy zio_delay
The time elapsed (in nanoseconds) waiting for the block layer to complete the
I/O request.
Unlike
.Sy zio_delta ,
this does not include any vdev queuing time and is
therefore solely a measure of the block layer performance.
.It Sy zio_timestamp
The time when a given I/O request was submitted.
.It Sy zio_delta
The time required to service a given I/O request.
.It Sy prev_state
The previous state of the vdev.
.It Sy cksum_expected
The expected checksum value for the block.
.It Sy cksum_actual
The actual checksum value for an errant block.
.It Sy cksum_algorithm
Checksum algorithm used.
See
.Xr zfsprops 8
for more information on the available checksum algorithms.
.It Sy cksum_byteswap
Whether or not the data is byteswapped.
.It Sy bad_ranges
.No [\& Ns Ar start , end )
pairs of corruption offsets.
Offsets are always aligned on a 64-bit boundary,
and can include some gaps of non-corruption.
(See
.Sy bad_ranges_min_gap )
.It Sy bad_ranges_min_gap
In order to bound the size of the
.Sy bad_ranges
array, gaps of non-corruption
less than or equal to
.Sy bad_ranges_min_gap
bytes have been merged with
adjacent corruption.
Always at least 8 bytes, since corruption is detected on a 64-bit word basis.
.It Sy bad_range_sets
This array has one element per range in
.Sy bad_ranges .
Each element contains
the count of bits in that range which were clear in the good data and set
in the bad data.
.It Sy bad_range_clears
This array has one element per range in
.Sy bad_ranges .
Each element contains
the count of bits for that range which were set in the good data and clear in
the bad data.
.It Sy bad_set_bits
If this field exists, it is an array of
.Pq Ar bad data No & ~( Ns Ar good data ) ;
that is, the bits set in the bad data which are cleared in the good data.
Each element corresponds a byte whose offset is in a range in
.Sy bad_ranges ,
and the array is ordered by offset.
Thus, the first element is the first byte in the first
.Sy bad_ranges
range, and the last element is the last byte in the last
.Sy bad_ranges
range.
.It Sy bad_cleared_bits
Like
.Sy bad_set_bits ,
but contains
.Pq Ar good data No & ~( Ns Ar bad data ) ;
that is, the bits set in the good data which are cleared in the bad data.
.It Sy bad_set_histogram
If this field exists, it is an array of counters.
Each entry counts bits set in a particular bit of a big-endian uint64 type.
The first entry counts bits
set in the high-order bit of the first byte, the 9th byte, etc, and the last
entry counts bits set of the low-order bit of the 8th byte, the 16th byte, etc.
This information is useful for observing a stuck bit in a parallel data path,
such as IDE or parallel SCSI.
.It Sy bad_cleared_histogram
If this field exists, it is an array of counters.
Each entry counts bit clears in a particular bit of a big-endian uint64 type.
The first entry counts bits
clears of the high-order bit of the first byte, the 9th byte, etc, and the
last entry counts clears of the low-order bit of the 8th byte, the 16th byte, etc.
This information is useful for observing a stuck bit in a parallel data
path, such as IDE or parallel SCSI.
.El
.
.Sh I/O STAGES
The ZFS I/O pipeline is comprised of various stages which are defined below.
The individual stages are used to construct these basic I/O
operations: Read, Write, Free, Claim, and Ioctl.
These stages may be
set on an event to describe the life cycle of a given I/O request.
.Pp
.TS
tab(:);
l l l .
Stage:Bit Mask:Operations
_:_:_
ZIO_STAGE_OPEN:0x00000001:RWFCI

ZIO_STAGE_READ_BP_INIT:0x00000002:R----
ZIO_STAGE_WRITE_BP_INIT:0x00000004:-W---
ZIO_STAGE_FREE_BP_INIT:0x00000008:--F--
ZIO_STAGE_ISSUE_ASYNC:0x00000010:RWF--
ZIO_STAGE_WRITE_COMPRESS:0x00000020:-W---

ZIO_STAGE_ENCRYPT:0x00000040:-W---
ZIO_STAGE_CHECKSUM_GENERATE:0x00000080:-W---

ZIO_STAGE_NOP_WRITE:0x00000100:-W---

ZIO_STAGE_DDT_READ_START:0x00000200:R----
ZIO_STAGE_DDT_READ_DONE:0x00000400:R----
ZIO_STAGE_DDT_WRITE:0x00000800:-W---
ZIO_STAGE_DDT_FREE:0x00001000:--F--

ZIO_STAGE_GANG_ASSEMBLE:0x00002000:RWFC-
ZIO_STAGE_GANG_ISSUE:0x00004000:RWFC-

ZIO_STAGE_DVA_THROTTLE:0x00008000:-W---
ZIO_STAGE_DVA_ALLOCATE:0x00010000:-W---
ZIO_STAGE_DVA_FREE:0x00020000:--F--
ZIO_STAGE_DVA_CLAIM:0x00040000:---C-

ZIO_STAGE_READY:0x00080000:RWFCI

ZIO_STAGE_VDEV_IO_START:0x00100000:RW--I
ZIO_STAGE_VDEV_IO_DONE:0x00200000:RW--I
ZIO_STAGE_VDEV_IO_ASSESS:0x00400000:RW--I

ZIO_STAGE_CHECKSUM_VERIFY:0x00800000:R----

ZIO_STAGE_DONE:0x01000000:RWFCI
.TE
.
.Sh I/O FLAGS
Every I/O request in the pipeline contains a set of flags which describe its
function and are used to govern its behavior.
These flags will be set in an event as a
.Sy zio_flags
payload entry.
.Pp
.TS
tab(:);
l l .
Flag:Bit Mask
_:_
ZIO_FLAG_DONT_AGGREGATE:0x00000001
ZIO_FLAG_IO_REPAIR:0x00000002
ZIO_FLAG_SELF_HEAL:0x00000004
ZIO_FLAG_RESILVER:0x00000008
ZIO_FLAG_SCRUB:0x00000010
ZIO_FLAG_SCAN_THREAD:0x00000020
ZIO_FLAG_PHYSICAL:0x00000040

ZIO_FLAG_CANFAIL:0x00000080
ZIO_FLAG_SPECULATIVE:0x00000100
ZIO_FLAG_CONFIG_WRITER:0x00000200
ZIO_FLAG_DONT_RETRY:0x00000400
ZIO_FLAG_DONT_CACHE:0x00000800
ZIO_FLAG_NODATA:0x00001000
ZIO_FLAG_INDUCE_DAMAGE:0x00002000

ZIO_FLAG_IO_ALLOCATING:0x00004000
ZIO_FLAG_IO_RETRY:0x00008000
ZIO_FLAG_PROBE:0x00010000
ZIO_FLAG_TRYHARD:0x00020000
ZIO_FLAG_OPTIONAL:0x00040000

ZIO_FLAG_DONT_QUEUE:0x00080000
ZIO_FLAG_DONT_PROPAGATE:0x00100000
ZIO_FLAG_IO_BYPASS:0x00200000
ZIO_FLAG_IO_REWRITE:0x00400000
ZIO_FLAG_RAW_COMPRESS:0x00800000
ZIO_FLAG_RAW_ENCRYPT:0x01000000

ZIO_FLAG_GANG_CHILD:0x02000000
ZIO_FLAG_DDT_CHILD:0x04000000
ZIO_FLAG_GODFATHER:0x08000000
ZIO_FLAG_NOPWRITE:0x10000000
ZIO_FLAG_REEXECUTED:0x20000000
ZIO_FLAG_DELEGATED:0x40000000
ZIO_FLAG_FASTWRITE:0x80000000
.TE