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Update ReplacingDisks.md
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DjP-iX committed Dec 13, 2024
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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.

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.

### Replacing a Failed Disk Without a Hot Spare

If you are replacing the failed disk you took offline and removed, insert the replacement disk now.
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:
#### Detaching a Failed Disk

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

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 @@ -134,21 +133,21 @@ 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 >}}

WHAT IF I DO NOT HAVE A HOT SPARE/A SYSTEM WHICH DOES NOT SUPPORT HOT SWAPPING? <<< Offline/reboot process described here >>>

If recreating the spare with a replacement in place of the failed disk, insert the replacement disk now.
The new disk must have the same or greater capacity as the failed disk.
If recreating the spare with an available disk in the system, proceed to the next step.
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