ZFS-EVENTS(5)

NAME
zfs-events - Events created by the ZFS filesystem.

DESCRIPTION

Description of the different events generated by the ZFS stack.

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.

To view all events created since the loading of the ZFS infrastructure (i.e, "the module"), run

zpool events

to get a short list, and

zpool events -v

to get a full detail of the events and what information is available about it.

This man page lists the different subclasses that are issued in the case of an event. The full event name would be ereport.fs.zfs.SUBCLASS, but we only list the last part here.

  EVENTS (SUBCLASS)

checksum
    Issued when a checksum error has been detected.

io
    Issued when there is an I/O error in a vdev in the pool.

data
    Issued when there have been data errors in the pool.

deadman
    Issued when an I/O is determined to be "hung", this can be caused by lost completion events due to flaky hardware or drivers. See the zfs_deadman_failmode module option description for additional information regarding "hung" I/O detection and configuration.

delay
    Issued when a completed I/O exceeds the maximum allowed time specified by the zio_slow_io_ms module option. This can be an indicator of problems with the underlying storage device. The number of delay events is ratelimited by the zfs_slow_io_events_per_second module parameter.

config.sync
    Issued every time a vdev change have been done to the pool.

zpool
    Issued when a pool cannot be imported.

zpool.destroy
    Issued when a pool is destroyed.

zpool.export
    Issued when a pool is exported.

zpool.import
    Issued when a pool is imported.

zpool.reguid
    Issued when a REGUID (new unique identifier for the pool have been regenerated) have been detected.

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.

vdev.open_failed
    Issued when a vdev could not be opened (because it didn't exist for example).

vdev.corrupt_data
    Issued when corrupt data have been detected on a vdev.

vdev.no_replicas
    Issued when there are no more replicas to sustain the pool. This would lead to the pool being DEGRADED.

vdev.bad_guid_sum
    Issued when a missing device in the pool have been detected.

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 probe_failure event.

vdev.bad_label
    Issued when the label is OK but invalid.

vdev.bad_ashift
    Issued when the ashift alignment requirement has increased.

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).

vdev.clear
    Issued when clearing device errors in a pool. Such as running zpool clear on a device in the pool.

vdev.check
    Issued when a check to see if a given vdev could be opened is started.

vdev.spare
    Issued when a spare have kicked in to replace a failed device.

vdev.autoexpand
    Issued when a vdev can be automatically expanded.

io_failure
    Issued when there is an I/O failure in a vdev in the pool.

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).

log_replay
    Issued when the intent log cannot be replayed. The can occur in the case of a missing or damaged log device.

resilver.start
    Issued when a resilver is started.

resilver.finish
    Issued when the running resilver have finished.

scrub.start
    Issued when a scrub is started on a pool.

scrub.finish
    Issued when a pool has finished scrubbing.

scrub.abort
    Issued when a scrub is aborted on a pool.

scrub.resume
    Issued when a scrub is resumed on a pool.

scrub.paused
    Issued when a scrub is paused on a pool.

bootfs.vdev.attach

  PAYLOADS

This is the payload (data, information) that accompanies an event.

For zed(8), these are set to uppercase and prefixed with ZEVENT_.

pool
    Pool name.

pool_failmode
    Failmode - wait, continue or panic. See zpool(8) (failmode property) for more information.

pool_guid
    The GUID of the pool.

pool_context
    The load state for the pool (0=none, 1=open, 2=import, 3=tryimport, 4=recover 5=error).

vdev_guid
    The GUID of the vdev in question (the vdev failing or operated upon with zpool clear etc).

vdev_type
    Type of vdev - disk, file, mirror etc. See zpool(8) under Virtual Devices for more information on possible values.

vdev_path
    Full path of the vdev, including any -partX.

vdev_devid
    ID of vdev (if any).

vdev_fru
    Physical FRU location.

vdev_state
    State of vdev (0=uninitialized, 1=closed, 2=offline, 3=removed, 4=failed to open, 5=faulted, 6=degraded, 7=healthy).

vdev_ashift
    The ashift value of the vdev.

vdev_complete_ts
    The time the last I/O completed for the specified vdev.

vdev_delta_ts
    The time since the last I/O completed for the specified vdev.

vdev_spare_paths
    List of spares, including full path and any -partX.

vdev_spare_guids
    GUID(s) of spares.

vdev_read_errors
    How many read errors that have been detected on the vdev.

vdev_write_errors
    How many write errors that have been detected on the vdev.

vdev_cksum_errors
    How many checksum errors that have been detected on the vdev.

parent_guid
    GUID of the vdev parent.

parent_type
    Type of parent. See vdev_type.

parent_path
    Path of the vdev parent (if any).

parent_devid
    ID of the vdev parent (if any).

zio_objset
    The object set number for a given I/O.

zio_object
    The object number for a given I/O.

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.

zio_blkid
    The block ID for a given I/O.

zio_err
    The errno for a failure when handling a given I/O. The errno is compatible with errno(3) with the value for EBADE (0x34) used to indicate ZFS checksum error.

zio_offset
    The offset in bytes of where to write the I/O for the specified vdev.

zio_size
    The size in bytes of the I/O.

zio_flags
    The current flags describing how the I/O should be handled. See the I/O FLAGS section for the full list of I/O flags.

zio_stage
    The current stage of the I/O in the pipeline. See the I/O STAGES section for a full list of all the I/O stages.

zio_pipeline
    The valid pipeline stages for the I/O. See the I/O STAGES section for a full list of all the I/O stages.

zio_delay
    The time elapsed (in nanoseconds) waiting for the block layer to complete the I/O. Unlike zio_delta this does not include any vdev queuing time and is therefore solely a measure of the block layer performance.

zio_timestamp
    The time when a given I/O was submitted.

zio_delta
    The time required to service a given I/O.

prev_state
    The previous state of the vdev.

cksum_expected
    The expected checksum value for the block.

cksum_actual
    The actual checksum value for an errant block.

cksum_algorithm
    Checksum algorithm used. See zfs(8) for more information on checksum algorithms available.

cksum_byteswap
    Whether or not the data is byteswapped.

bad_ranges
    [start, end) pairs of corruption offsets. Offsets are always aligned on a 64-bit boundary, and can include some gaps of non-corruption. (See bad_ranges_min_gap)

bad_ranges_min_gap
    In order to bound the size of the bad_ranges array, gaps of non-corruption less than or equal to 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.

bad_range_sets
    This array has one element per range in 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.

bad_range_clears
    This array has one element per range in 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.

bad_set_bits
    If this field exists, it is an array of: (bad data & ~(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 bad_ranges, and the array is ordered by offset. Thus, the first element is the first byte in the first bad_ranges range, and the last element is the last byte in the last bad_ranges range.

bad_cleared_bits
    Like bad_set_bits, but contains: (good data & ~(bad data)); that is, the bits set in the good data which are cleared in the bad data.

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.

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.

  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.
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

  I/O FLAGS

Every I/O 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 an zio_flags payload entry.
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