ZFS does not support online shrinking; this post focuses on operational tasks such as creating pools, replacing disks, and expanding capacity. 1. ZFS vdev Types mirror: mirroring, multiple disks hold copies of each other, equivalent to RAID 1 raidz3: triple parity, tolerates 3 disk failures raidz2: double parity, tolerates 2 disk failures, equivalent to RAID 6 raidz1: single parity, tolerates 1 disk failure, equivalent to RAID 5 striped: striping, no redundancy, equivalent to RAID 0 They can also be combined:

The xfs filesystem does not support shrinking. This post is mainly about disk replacement and expansion under RAID 10. 1. RAID States and Disk States In mdadm, the RAID states are: clean, normal degraded, still readable and writable, but with reduced fault tolerance reshaping, reorganization in progress, appears during expansion and shrinking resyncing, data synchronization in progress recovering, data recovery in progress, accompanied by degradation as a disk is rebuilt failed In mdadm, the disk states are:

Btrfs supports online expansion, shrinking, disk replacement, and RAID mode conversion; this post covers creating a filesystem under RAID 0/RAID 1/RAID 10/RAID 6 topologies, adding disks, replacing disks, shrinking, and common operational tasks. 1. Btrfs Profiles single: single copy, no redundancy, works with one disk or can aggregate multiple disks.

1. Disk Baseline Testing 1.1 4k Random Write 1 2 3 4 5 6 7 8 9 10 11 12 13 14 fio \ --name=4k_randwrite \ --rw=randwrite \ --bs=4k \ --ioengine=libaio \ --direct=1 \ --numjobs=8 \ --iodepth=32 \ --size=20G \ --time_based \ --runtime=120 \ --group_reporting \ --allow_mounted_write=1 \ --filename=/data1/fio-4k-randwrite.dat 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 Starting 8 processes 4k_randwrite: Laying out IO file (1 file / 20480MiB) Jobs: 8 (f=8): [w(8)][100.

1. What Is RAID RAID technology combines multiple physical hard drives into a single logical hard drive, so the operating system sees it as one storage device. There are two ways to implement RAID: hardware and software. A hardware implementation is a RAID controller, a standalone hardware device responsible for RAID control and management.