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diff --git a/upstream/archlinux/man8/btrfs-device.8 b/upstream/archlinux/man8/btrfs-device.8 new file mode 100644 index 00000000..5789f4fa --- /dev/null +++ b/upstream/archlinux/man8/btrfs-device.8 @@ -0,0 +1,484 @@ +.\" Man page generated from reStructuredText. +. +. +.nr rst2man-indent-level 0 +. +.de1 rstReportMargin +\\$1 \\n[an-margin] +level \\n[rst2man-indent-level] +level margin: \\n[rst2man-indent\\n[rst2man-indent-level]] +- +\\n[rst2man-indent0] +\\n[rst2man-indent1] +\\n[rst2man-indent2] +.. +.de1 INDENT +.\" .rstReportMargin pre: +. RS \\$1 +. nr rst2man-indent\\n[rst2man-indent-level] \\n[an-margin] +. nr rst2man-indent-level +1 +.\" .rstReportMargin post: +.. +.de UNINDENT +. RE +.\" indent \\n[an-margin] +.\" old: \\n[rst2man-indent\\n[rst2man-indent-level]] +.nr rst2man-indent-level -1 +.\" new: \\n[rst2man-indent\\n[rst2man-indent-level]] +.in \\n[rst2man-indent\\n[rst2man-indent-level]]u +.. +.TH "BTRFS-DEVICE" "8" "Feb 14, 2024" "6.7.1" "BTRFS" +.SH NAME +btrfs-device \- manage devices of btrfs filesystems +.SH SYNOPSIS +.sp +\fBbtrfs device\fP <subcommand> <args> +.SH DESCRIPTION +.sp +The \fBbtrfs device\fP command group is used to manage devices of the btrfs filesystems. +.SH DEVICE MANAGEMENT +.sp +BTRFS filesystem can be created on top of single or multiple block devices. +Devices can be then added, removed or replaced on demand. Data and metadata are +organized in allocation profiles with various redundancy policies. There\(aqs some +similarity with traditional RAID levels, but this could be confusing to users +familiar with the traditional meaning. Due to the similarity, the RAID +terminology is widely used in the documentation. See \fI\%mkfs.btrfs(8)\fP for more +details and the exact profile capabilities and constraints. +.sp +The device management works on a mounted filesystem. Devices can be added, +removed or replaced, by commands provided by \fBbtrfs device\fP and \fBbtrfs replace\fP\&. +.sp +The profiles can be also changed, provided there\(aqs enough workspace to do the +conversion, using the \fBbtrfs balance\fP command and namely the filter \fIconvert\fP\&. +.INDENT 0.0 +.TP +.B Type +The block group profile type is the main distinction of the information stored +on the block device. User data are called \fIData\fP, the internal data structures +managed by filesystem are \fIMetadata\fP and \fISystem\fP\&. +.TP +.B Profile +A profile describes an allocation policy based on the redundancy/replication +constraints in connection with the number of devices. The profile applies to +data and metadata block groups separately. E.g. \fIsingle\fP, \fIRAID1\fP\&. +.TP +.B RAID level +Where applicable, the level refers to a profile that matches constraints of the +standard RAID levels. At the moment the supported ones are: RAID0, RAID1, +RAID10, RAID5 and RAID6. +.UNINDENT +.SH TYPICAL USE CASES +.SS Starting with a single\-device filesystem +.sp +Assume we\(aqve created a filesystem on a block device \fB/dev/sda\fP with profile +\fIsingle/single\fP (data/metadata), the device size is 50GiB and we\(aqve used the +whole device for the filesystem. The mount point is \fB/mnt\fP\&. +.sp +The amount of data stored is 16GiB, metadata have allocated 2GiB. +.SS Add new device +.sp +We want to increase the total size of the filesystem and keep the profiles. The +size of the new device \fB/dev/sdb\fP is 100GiB. +.INDENT 0.0 +.INDENT 3.5 +.sp +.nf +.ft C +$ btrfs device add /dev/sdb /mnt +.ft P +.fi +.UNINDENT +.UNINDENT +.sp +The amount of free data space increases by less than 100GiB, some space is +allocated for metadata. +.SS Convert to RAID1 +.sp +Now we want to increase the redundancy level of both data and metadata, but +we\(aqll do that in steps. Note, that the device sizes are not equal and we\(aqll use +that to show the capabilities of split data/metadata and independent profiles. +.sp +The constraint for RAID1 gives us at most 50GiB of usable space and exactly 2 +copies will be stored on the devices. +.sp +First we\(aqll convert the metadata. As the metadata occupy less than 50GiB and +there\(aqs enough workspace for the conversion process, we can do: +.INDENT 0.0 +.INDENT 3.5 +.sp +.nf +.ft C +$ btrfs balance start \-mconvert=raid1 /mnt +.ft P +.fi +.UNINDENT +.UNINDENT +.sp +This operation can take a while, because all metadata have to be moved and all +block pointers updated. Depending on the physical locations of the old and new +blocks, the disk seeking is the key factor affecting performance. +.sp +You\(aqll note that the system block group has been also converted to RAID1, this +normally happens as the system block group also holds metadata (the physical to +logical mappings). +.sp +What changed: +.INDENT 0.0 +.IP \(bu 2 +available data space decreased by 3GiB, usable roughly (50 \- 3) + (100 \- 3) = 144 GiB +.IP \(bu 2 +metadata redundancy increased +.UNINDENT +.sp +IOW, the unequal device sizes allow for combined space for data yet improved +redundancy for metadata. If we decide to increase redundancy of data as well, +we\(aqre going to lose 50GiB of the second device for obvious reasons. +.INDENT 0.0 +.INDENT 3.5 +.sp +.nf +.ft C +$ btrfs balance start \-dconvert=raid1 /mnt +.ft P +.fi +.UNINDENT +.UNINDENT +.sp +The balance process needs some workspace (i.e. a free device space without any +data or metadata block groups) so the command could fail if there\(aqs too much +data or the block groups occupy the whole first device. +.sp +The device size of \fB/dev/sdb\fP as seen by the filesystem remains unchanged, but +the logical space from 50\-100GiB will be unused. +.SS Remove device +.sp +Device removal must satisfy the profile constraints, otherwise the command +fails. For example: +.INDENT 0.0 +.INDENT 3.5 +.sp +.nf +.ft C +$ btrfs device remove /dev/sda /mnt +ERROR: error removing device \(aq/dev/sda\(aq: unable to go below two devices on raid1 +.ft P +.fi +.UNINDENT +.UNINDENT +.sp +In order to remove a device, you need to convert the profile in this case: +.INDENT 0.0 +.INDENT 3.5 +.sp +.nf +.ft C +$ btrfs balance start \-mconvert=dup \-dconvert=single /mnt +$ btrfs device remove /dev/sda /mnt +.ft P +.fi +.UNINDENT +.UNINDENT +.SH SUBCOMMAND +.INDENT 0.0 +.TP +.B add [\-Kf] <device> [<device>...] <path> +Add device(s) to the filesystem identified by \fIpath\fP\&. +.sp +If applicable, a whole device discard (TRIM) operation is performed prior to +adding the device. A device with existing filesystem detected by \fBblkid(8)\fP +will prevent device addition and has to be forced. Alternatively the filesystem +can be wiped from the device using e.g. the \fBwipefs(8)\fP tool. +.sp +The operation is instant and does not affect existing data. The operation merely +adds the device to the filesystem structures and creates some block groups +headers. +.sp +\fBOptions\fP +.INDENT 7.0 +.TP +.B \-K|\-\-nodiscard +do not perform discard (TRIM) by default +.TP +.B \-f|\-\-force +force overwrite of existing filesystem on the given disk(s) +.UNINDENT +.INDENT 7.0 +.TP +.B \-\-enqueue +wait if there\(aqs another exclusive operation running, otherwise continue +.UNINDENT +.TP +.B remove [options] <device>|<devid> [<device>|<devid>...] <path> +Remove device(s) from a filesystem identified by <path> +.sp +Device removal must satisfy the profile constraints, otherwise the command +fails and cannot be enforced. The filesystem must be converted to +profile(s) that would allow the removal. This can for example happen when +going down from 2 devices to 1 and using the RAID1 profile. See the +section \fI\%Typical use cases\fP\&. +.sp +The operation can take long as it needs to move all data from the device. +.sp +\fBNOTE:\fP +.INDENT 7.0 +.INDENT 3.5 +It\(aqs possible to specify more than one device on the command +line but the devices will be removed one by one, not at once. +This means that the remaining devices to be deleted can be +still used for writes. In that case there\(aqs a warning and safety +timeout as this can be confusing and unexpected. The timeout can +be overridden by option \fI\-\-force\fP\&. +.UNINDENT +.UNINDENT +.sp +It is possible to delete the device that was used to mount the filesystem. The +device entry in the mount table (\fB/proc/self/mounts\fP) will be +replaced by another device name with the lowest device id. +.sp +If the filesystem is mounted in degraded mode (\fI\-o degraded\fP), special term +\fImissing\fP can be used for \fIdevice\fP\&. In that case, the first device that is +described by the filesystem metadata, but not present at the mount time will be +removed. +.sp +\fBNOTE:\fP +.INDENT 7.0 +.INDENT 3.5 +In most cases, there is only one missing device in degraded mode, +otherwise mount fails. If there are two or more devices missing (e.g. possible +in RAID6), you need specify \fImissing\fP as many times as the number of missing +devices to remove all of them. +.UNINDENT +.UNINDENT +.sp +\fBOptions\fP +.INDENT 7.0 +.TP +.B \-\-enqueue +wait if there\(aqs another exclusive operation running, otherwise continue +.TP +.B \-\-force +skip the safety timeout when there are multiple devices for removal, this +does not force removing devices that would break the profile constraints +.UNINDENT +.TP +.B delete <device>|<devid> [<device>|<devid>...] <path> +Alias of remove kept for backward compatibility +.TP +.B replace <command> [options] <path> +Alias of whole command group \fIbtrfs replace\fP for convenience. See +\fI\%btrfs\-replace(8)\fP\&. +.TP +.B ready <device> +Wait until all devices of a multiple\-device filesystem are scanned and +registered within the kernel module. This is to provide a way for automatic +filesystem mounting tools to wait before the mount can start. The device scan +is only one of the preconditions and the mount can fail for other reasons. +Normal users usually do not need this command and may safely ignore it. +.TP +.B scan [options] [<device> [<device>...]] +Scan devices for a btrfs filesystem and register them with the kernel module. +This allows mounting multiple\-device filesystem by specifying just one from the +whole group. +.sp +If no devices are passed, all block devices that blkid reports to contain btrfs +are scanned. +.sp +The options \fI\-\-all\-devices\fP or \fI\-d\fP can be used as a fallback in case blkid is +not available. If used, behavior is the same as if no devices are passed. +.sp +The command can be run repeatedly. Devices that have been already registered +remain as such. Reloading the kernel module will drop this information. There\(aqs +an alternative way of mounting multiple\-device filesystem without the need for +prior scanning. See the mount option +\fI\%device (in btrfs\-man5)\fP\&. +.sp +\fBOptions\fP +.INDENT 7.0 +.TP +.B \-d|\-\-all\-devices +Enumerate and register all devices, use as a fallback in case blkid is not +available. +.TP +.B \-u|\-\-forget +Unregister a given device or all stale devices if no path is given, the device +must be unmounted otherwise it\(aqs an error. +.UNINDENT +.TP +.B stats [options] <path>|<device> +Read and print the device IO error statistics for all devices of the given +filesystem identified by \fIpath\fP or for a single \fIdevice\fP\&. The filesystem must +be mounted. See section \fI\%DEVICE STATS\fP +for more information about the reported statistics and the meaning. +.sp +\fBOptions\fP +.INDENT 7.0 +.TP +.B \-z|\-\-reset +Print the stats and reset the values to zero afterwards. +.TP +.B \-c|\-\-check +Check if the stats are all zeros and return 0 if it is so. Set bit 6 of the +return code if any of the statistics is no\-zero. The error values is 65 if +reading stats from at least one device failed, otherwise it\(aqs 64. +.UNINDENT +.INDENT 7.0 +.TP +.B \-T +Print stats in a tabular form, devices as rows and stats as columns +.UNINDENT +.TP +.B usage [options] <path> [<path>...]:: +Show detailed information about internal allocations on devices. +.sp +The level of detail can differ if the command is run under a regular or the +root user (due to use of restricted ioctls). The first example below is for +normal user (warning included) and the next one with root on the same +filesystem: +.INDENT 7.0 +.INDENT 3.5 +.sp +.nf +.ft C +WARNING: cannot read detailed chunk info, per\-device usage will not be shown, run as root +/dev/sdc1, ID: 1 + Device size: 931.51GiB + Device slack: 0.00B + Unallocated: 931.51GiB + +/dev/sdc1, ID: 1 + Device size: 931.51GiB + Device slack: 0.00B + Data,single: 641.00GiB + Data,RAID0/3: 1.00GiB + Metadata,single: 19.00GiB + System,single: 32.00MiB + Unallocated: 271.48GiB +.ft P +.fi +.UNINDENT +.UNINDENT +.INDENT 7.0 +.IP \(bu 2 +\fIDevice size\fP \-\- size of the device as seen by the filesystem (may be +different than actual device size) +.IP \(bu 2 +\fIDevice slack\fP \-\- portion of device not used by the filesystem but +still available in the physical space provided by the device, e.g. +after a device shrink +.IP \(bu 2 +\fIData,single\fP, \fIMetadata,single\fP, \fISystem,single\fP \-\- in general, list +of block group type (Data, Metadata, System) and profile (single, +RAID1, ...) allocated on the device +.IP \(bu 2 +\fIData,RAID0/3\fP \-\- in particular, striped profiles +RAID0/RAID10/RAID5/RAID6 with the number of devices on which the +stripes are allocated, multiple occurrences of the same profile can +appear in case a new device has been added and all new available +stripes have been used for writes +.IP \(bu 2 +\fIUnallocated\fP \-\- remaining space that the filesystem can still use +for new block groups +.UNINDENT +.sp +\fBOptions\fP +.INDENT 7.0 +.TP +.B \-b|\-\-raw +raw numbers in bytes, without the \fIB\fP suffix +.TP +.B \-h|\-\-human\-readable +print human friendly numbers, base 1024, this is the default +.UNINDENT +.INDENT 7.0 +.TP +.B \-H +print human friendly numbers, base 1000 +.TP +.B \-\-iec +select the 1024 base for the following options, according to the IEC standard +.TP +.B \-\-si +select the 1000 base for the following options, according to the SI standard +.UNINDENT +.INDENT 7.0 +.TP +.B \-k|\-\-kbytes +show sizes in KiB, or kB with \-\-si +.TP +.B \-m|\-\-mbytes +show sizes in MiB, or MB with \-\-si +.TP +.B \-g|\-\-gbytes +show sizes in GiB, or GB with \-\-si +.TP +.B \-t|\-\-tbytes +show sizes in TiB, or TB with \-\-si +.UNINDENT +.sp +If conflicting options are passed, the last one takes precedence. +.UNINDENT +.SH DEVICE STATS +.sp +The device stats keep persistent record of several error classes related to +doing IO. The current values are printed at mount time and updated during +filesystem lifetime or from a scrub run. +.INDENT 0.0 +.INDENT 3.5 +.sp +.nf +.ft C +$ btrfs device stats /dev/sda3 +[/dev/sda3].write_io_errs 0 +[/dev/sda3].read_io_errs 0 +[/dev/sda3].flush_io_errs 0 +[/dev/sda3].corruption_errs 0 +[/dev/sda3].generation_errs 0 +.ft P +.fi +.UNINDENT +.UNINDENT +.INDENT 0.0 +.TP +.B write_io_errs +Failed writes to the block devices, means that the layers beneath the +filesystem were not able to satisfy the write request. +.TP +.B read_io_errors +Read request analogy to write_io_errs. +.TP +.B flush_io_errs +Number of failed writes with the \fIFLUSH\fP flag set. The flushing is a method of +forcing a particular order between write requests and is crucial for +implementing crash consistency. In case of btrfs, all the metadata blocks must +be permanently stored on the block device before the superblock is written. +.TP +.B corruption_errs +A block checksum mismatched or a corrupted metadata header was found. +.TP +.B generation_errs +The block generation does not match the expected value (e.g. stored in the +parent node). +.UNINDENT +.sp +Since kernel 5.14 the device stats are also available in textual form in +\fB/sys/fs/btrfs/FSID/devinfo/DEVID/error_stats\fP\&. +.SH EXIT STATUS +.sp +\fBbtrfs device\fP returns a zero exit status if it succeeds. Non zero is +returned in case of failure. +.sp +If the \fI\-c\fP option is used, \fIbtrfs device stats\fP will add 64 to the +exit status if any of the error counters is non\-zero. +.SH AVAILABILITY +.sp +\fBbtrfs\fP is part of btrfs\-progs. Please refer to the documentation at +\fI\%https://btrfs.readthedocs.io\fP\&. +.SH SEE ALSO +.sp +\fI\%btrfs\-balance(8)\fP +\fI\%btrfs\-device(8)\fP, +\fI\%btrfs\-replace(8)\fP, +\fI\%mkfs.btrfs(8)\fP +.\" Generated by docutils manpage writer. +. |