ZFS-EVENTS

Index

NAME

DESCRIPTION

EVENTS (SUBCLASS)

PAYLOADS

I/O STAGES

I/O FLAGS

NAME

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

zpool events -v

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 checkum 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 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