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