1.\" SPDX-License-Identifier: CDDL-1.0 2.\" 3.\" CDDL HEADER START 4.\" 5.\" The contents of this file are subject to the terms of the 6.\" Common Development and Distribution License (the "License"). 7.\" You may not use this file except in compliance with the License. 8.\" 9.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 10.\" or https://opensource.org/licenses/CDDL-1.0. 11.\" See the License for the specific language governing permissions 12.\" and limitations under the License. 13.\" 14.\" When distributing Covered Code, include this CDDL HEADER in each 15.\" file and include the License file at usr/src/OPENSOLARIS.LICENSE. 16.\" If applicable, add the following below this CDDL HEADER, with the 17.\" fields enclosed by brackets "[]" replaced with your own identifying 18.\" information: Portions Copyright [yyyy] [name of copyright owner] 19.\" 20.\" CDDL HEADER END 21.\" 22.\" Copyright (c) 2007, Sun Microsystems, Inc. All Rights Reserved. 23.\" Copyright (c) 2012, 2018 by Delphix. All rights reserved. 24.\" Copyright (c) 2012 Cyril Plisko. All Rights Reserved. 25.\" Copyright (c) 2017 Datto Inc. 26.\" Copyright (c) 2018 George Melikov. All Rights Reserved. 27.\" Copyright 2017 Nexenta Systems, Inc. 28.\" Copyright (c) 2017 Open-E, Inc. All Rights Reserved. 29.\" 30.Dd June 28, 2023 31.Dt ZPOOL-ATTACH 8 32.Os 33. 34.Sh NAME 35.Nm zpool-attach 36.Nd attach new device to existing ZFS vdev 37.Sh SYNOPSIS 38.Nm zpool 39.Cm attach 40.Op Fl fsw 41.Oo Fl o Ar property Ns = Ns Ar value Oc 42.Ar pool device new_device 43. 44.Sh DESCRIPTION 45Attaches 46.Ar new_device 47to the existing 48.Ar device . 49The behavior differs depending on if the existing 50.Ar device 51is a RAID-Z device, or a mirror/plain device. 52.Pp 53If the existing device is a mirror or plain device 54.Pq e.g. specified as Qo Li sda Qc or Qq Li mirror-7 , 55the new device will be mirrored with the existing device, a resilver will be 56initiated, and the new device will contribute to additional redundancy once the 57resilver completes. 58If 59.Ar device 60is not currently part of a mirrored configuration, 61.Ar device 62automatically transforms into a two-way mirror of 63.Ar device 64and 65.Ar new_device . 66If 67.Ar device 68is part of a two-way mirror, attaching 69.Ar new_device 70creates a three-way mirror, and so on. 71In either case, 72.Ar new_device 73begins to resilver immediately and any running scrub is canceled. 74.Pp 75If the existing device is a RAID-Z device 76.Pq e.g. specified as Qq Ar raidz2-0 , 77the new device will become part of that RAID-Z group. 78A "raidz expansion" will be initiated, and once the expansion completes, 79the new device will contribute additional space to the RAID-Z group. 80The expansion entails reading all allocated space from existing disks in the 81RAID-Z group, and rewriting it to the new disks in the RAID-Z group (including 82the newly added 83.Ar device ) . 84Its progress can be monitored with 85.Nm zpool Cm status . 86.Pp 87Data redundancy is maintained during and after the expansion. 88If a disk fails while the expansion is in progress, the expansion pauses until 89the health of the RAID-Z vdev is restored (e.g. by replacing the failed disk 90and waiting for reconstruction to complete). 91Expansion does not change the number of failures that can be tolerated 92without data loss (e.g. a RAID-Z2 is still a RAID-Z2 even after expansion). 93A RAID-Z vdev can be expanded multiple times. 94.Pp 95After the expansion completes, old blocks retain their old data-to-parity 96ratio 97.Pq e.g. 5-wide RAID-Z2 has 3 data and 2 parity 98but distributed among the larger set of disks. 99New blocks will be written with the new data-to-parity ratio (e.g. a 5-wide 100RAID-Z2 which has been expanded once to 6-wide, has 4 data and 2 parity). 101However, the vdev's assumed parity ratio does not change, so slightly less 102space than is expected may be reported for newly-written blocks, according to 103.Nm zfs Cm list , 104.Nm df , 105.Nm ls Fl s , 106and similar tools. 107.Pp 108A pool-wide scrub is initiated at the end of the expansion in order to verify 109the checksums of all blocks which have been copied during the expansion. 110.Bl -tag -width Ds 111.It Fl f 112Forces use of 113.Ar new_device , 114even if it appears to be in use. 115Not all devices can be overridden in this manner. 116.It Fl o Ar property Ns = Ns Ar value 117Sets the given pool properties. 118See the 119.Xr zpoolprops 7 120manual page for a list of valid properties that can be set. 121The only property supported at the moment is 122.Sy ashift . 123.It Fl s 124When attaching to a mirror or plain device, the 125.Ar new_device 126is reconstructed sequentially to restore redundancy as quickly as possible. 127Checksums are not verified during sequential reconstruction so a scrub is 128started when the resilver completes. 129.It Fl w 130Waits until 131.Ar new_device 132has finished resilvering or expanding before returning. 133.El 134. 135.Sh SEE ALSO 136.Xr zpool-add 8 , 137.Xr zpool-detach 8 , 138.Xr zpool-import 8 , 139.Xr zpool-initialize 8 , 140.Xr zpool-online 8 , 141.Xr zpool-replace 8 , 142.Xr zpool-resilver 8 143