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Reorganize ReplacingDisks.md to avoid confusion #3366

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Reorganize ReplacingDisks.md to avoid confusion #3366

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Update ReplacingDisks.md with suggestion for non-hot swappable systems
Aviatorpaal Dec 13, 2024
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Update ReplacingDisks.md
DjP-iX Dec 13, 2024
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59 changes: 30 additions & 29 deletions content/SCALETutorials/Storage/Disks/ReplacingDisks.md
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Looks great! Thanks for cleaning it up

Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,21 @@ TrueNAS wipes the data on the replacement disk as part of the process.
Disk replacement automatically triggers a pool resilver.
{{< /hint >}}

This tutorial includes instructions for replacing a failed disk in TrueNAS systems with and without an available hot spare.
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What if the users have systems which do not allow hot plug or hot swapping their JBOD HDDs? There should be a section describing the "offlining", detaching and rebooting process in this case, as not all will do this with their systems operational.


To replace a disk in a pool without a hot spare available:

1. [Take the disk offline](#taking-a-failed-disk-offline).
2. [Replace the disk](#replacing-a-failed-disk-without-a-hot-spare).
3. Refresh the screen.

To replace a disk in a pool with a hot spare:

1. [Take the disk offline](#taking-a-failed-disk-offline).
2. [Detach the failed disk](#detaching-a-failed-disk) to promote the hot spare.
3. Refresh the screen.
4. [Recreate the hot spare VDEV](#recreating-a-hot-spare).

## Replacing a Failed Disk

If you configure your main SCALE **Dashboard** to include individual **Pool** or the **Storage** widgets they show the status of your system pools as on or offline, degraded, or in an error condition.
Expand All @@ -50,20 +65,7 @@ We do not recommend leaving failed disks online unless you know the exact condit
Attempting to replace a heavily degraded disk without off-lining it significantly slows down the replacement process.
{{< /expand >}}

To replace a disk in a pool without a hot spare available:

1. [Take the disk offline](#taking-a-failed-disk-offline).
2. [Replace the disk](#replacing-a-failed-disk).
3. Refresh the screen.

To replace a disk in a pool with a hot spare:

1. [Take the disk offline](#taking-a-failed-disk-offline).
2. [Detach the failed disk](#detaching-a-failed-disk) to promote the hot spare.
3. Refresh the screen.
4. [Recreate the hot spare VDEV](#recreating-the-hot-spare).

## Taking a Failed Disk Offline
### Taking a Failed Disk Offline

We recommend users off-line a disk before starting the physical disk replacement.
Off-lining a disk removes the device from the pool and can prevent swap issues.
Expand All @@ -85,9 +87,11 @@ If the off-line operation fails with a **Disk offline failed - no valid replicas
When the scrub operation finishes, return to the **Devices** screen, expand the VDEV, then click the disk, and try to off-line it again.
{{< /expand >}}

## Replacing a Failed Disk
After offlining the failed disk, physically remove it from the system.

If you are replacing the failed disk you took offline and removed, insert the replacement disk now.
### Replacing a Failed Disk Without a Hot Spare

After [taking the failed disk offline](#taking-a-failed-disk-offline) and physically removing it from the system, insert the replacement disk now.
The new disk must have the same or greater capacity as the failed disk.
If replacing a failed disk with an available disk in the system, proceed to the next step.

Expand All @@ -109,22 +113,17 @@ TrueNAS resilvers the pool during the replacement process.
For pools with large amounts of data, this can take a long time.
When the resilver process completes, the pool status returns to **Online** on the **Devices** screen.

## Replacing a Failed Disk with a Hot Spare
Refresh the screen to ensure the replacement disk appears in the pool as expected.

### Replacing a Failed Disk With a Hot Spare

A **Hot Spare** vdev sets up drives as reserved to prevent larger pool and data loss scenarios.
TrueNAS automatically inserts an available hot spare into a **Data** vdev when an active drive fails.
TrueNAS resilvers the pool after the hot spare is activated.

To replace a disk in a pool with a hot spare:

1. [Take the disk offline](#taking-a-failed-disk-offline).
2. [Detach the failed disk](#detaching-a-failed-disk) to promote the hot spare.
3. Refresh the screen.
4. [Recreate the hot spare VDEV](#recreating-the-hot-spare).

### Detaching a Failed Disk
#### Detaching a Failed Disk

Go to the **Storage Dashboard** and click **Manage Devices** on the **Topology** widget for the degraded pool to open the **Devices** screen for that pool.
After [taking the failed disk offline](#taking-a-failed-disk-offline) and physically removing it from the system, go to the **Storage Dashboard** and click **Manage Devices** on the **Topology** widget for the degraded pool to open the **Devices** screen for that pool.
Click <span class="iconify" data-icon="mdi:keyboard-arrow-right"></span> next to the VDEV to expand it, then look for the disk with the **REMOVED** status.

{{< trueimage src="/images/SCALE/Storage/DevicesDiskDegradedHotSpare.png" alt="Devices Disk Failed - Hot Spare Active" id="Devices Disk Failed - Hot Spare Active" >}}
Expand All @@ -134,17 +133,19 @@ Click **Detach** on the **ZFS Info** widget on the **Devices** screen for the di
Select **Confirm**, then click **Detach**.
TrueNAS detaches the disk from the pool and promotes the hot spare disk to a full member of the pool.

### Recreating the Hot Spare
Refresh the screen to ensure the promoted hot spare appears in the pool as expected.

#### Recreating a Hot Spare

After promoting the hot spare, recreate the **Spare** vdev and assign a disk to it.

{{< expand "Do I really need to promote the hot spare and then recreate the spare vdev?" "v" >}}
If you have a hot spare inserted into the pool and then follow the instructions in [Replacing a Failed Disk](#replacing-a-failed-disk), TrueNAS automatically returns the hot spare disk to the existing **Spare** vdev and **ONLINE** status.
If you have a hot spare inserted into the pool and then follow the instructions in [Replacing a Failed Disk Without a Hot Spare](#replacing-a-failed-disk-without-a-hot-spare), TrueNAS automatically returns the hot spare disk to the existing **Spare** vdev and **ONLINE** status.

However, we do not recommend this method, because it causes two resilver events: one when activating the hot spare and again when replacing the failed disk.
Resilvering degrades system performance until completed and causes unnecessary strain on the disk.

To avoid unnecessary resilvers, [promote the hot spare](#detaching-a-failed-disk) then recreate the hot spare vdev.
To avoid unnecessary resilvers, promote the hot spare by [detaching the failed disk]](#detaching-a-failed-disk) then recreate the hot spare vdev.
{{< /expand >}}

If recreating the spare with a replacement in place of the failed disk, insert the replacement disk now.
Expand Down