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Oracle Solaris 11.4 ZFS Device Removal Example

One of the new features in the recent Solaris 11.4 release(that rely rocks), is, ZFS Device Removal.

Below I am going to demonstrated one example, on how you can use ZFS Device Removal.

The example below show how migrated a pool from raidz1 => mirrored pool.

First, lets create a test directory with test files, do so by running the below.

mkdir test && cd test

Lets prepare / create test files to use in this test.

for i in {1..7}; do mkfile 175m file$i;done

Next, lets create a test pool.

zpool create testPool raidz1 /root/test/file1  /root/test/file2 /root/test/file3

Lets see the newly create raidz1 pool.

zpool status testPool
  pool: testPool
 state: ONLINE
  scan: none requested
config:

        NAME                  STATE      READ WRITE CKSUM
        testPool              ONLINE        0     0     0
          raidz1-0            ONLINE        0     0     0
            /root/test/file1  ONLINE        0     0     0
            /root/test/file2  ONLINE        0     0     0
            /root/test/file3  ONLINE        0     0     0

errors: No known data errors

The goal of the next exercise is to convert the testPool from raidz1 to a mirrored configuration.

To accomplish that, we are going to add a new mirror to the existing pool.

zpool add testPool mirror /root/test/file4  /root/test/file5 mirror /root/test/file6 /root/test/file7
vdev verification failed: use -f to override the following errors:
mismatched replication level: pool uses raidz and new vdev is mirror
Unable to build pool from specified devices: invalid vdev configuration

So running the above gives you a warning to not mix raid types, typicality not a good practice in a normal environment.

So lets force adding the newly mirrored raid disks (as this is a pre- requisite to the migration/removal), by adding a -f.

zpool add -f testPool mirror /root/test/file4  /root/test/file5 mirror /root/test/file6 /root/test/file7

Lets take a look on the pool.

zpool status testPool
  pool: testPool
 state: ONLINE
  scan: none requested
config:

        NAME                  STATE      READ WRITE CKSUM
        testPool              ONLINE        0     0     0
          raidz1-0            ONLINE        0     0     0
            /root/test/file1  ONLINE        0     0     0
            /root/test/file2  ONLINE        0     0     0
            /root/test/file3  ONLINE        0     0     0
          mirror-1            ONLINE        0     0     0
            /root/test/file4  ONLINE        0     0     0
            /root/test/file5  ONLINE        0     0     0
          mirror-2            ONLINE        0     0     0
            /root/test/file6  ONLINE        0     0     0
            /root/test/file7  ONLINE        0     0     0

errors: No known data errors

As you can see from the zpool status output above. the zpool now contains a mix of raidz and a mirror.

We are now ready for prime time test. so lets remove the raidz raid set.
You do that by simply running the below.

zpool remove testPool raidz1-0

Now, lets take a look on the zpool status.
As you can see below, we are only left with the mirrored configuration.

zpool status testPool
  pool: testPool
 state: ONLINE
  scan: resilvered 17.5K in 1s with 0 errors on Tue Aug 28 12:33:14 2018

config:

        NAME                      STATE      READ WRITE CKSUM
        testPool                  ONLINE        0     0     0
          mirror-1                ONLINE        0     0     0
            /root/test/file4      ONLINE        0     0     0
            /root/test/file5      ONLINE        0     0     0
          mirror-2                ONLINE        0     0     0
            /root/test/file6      ONLINE        0     0     0
            /root/test/file7      ONLINE        0     0     0

errors: No known data errors

Thats all it takes to trigger the ZFS device removal option.

Cleaning up.
Just run the below to remove your pool and remove the testing files.

zpool destroy testPool
rm file[1-7]

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