Administrators can insert a disk into a running node as long as the server hardware supports this function. Replacing failed disks (hot swapping) or adding additional disks (hot plugging) is supported without a server reboot.

Swarm recognizes, formats, and mounts the disk as a new volume when inserting a new unformatted disk. The disk continues to function as a volume without data loss when inserting a Swarm-formatted disk into the same node or a different node. The volume remains retired if the formatted disk was previously retired.

No manual configuration or intervention is needed. Messages are displayed in logs and in the Swarm Admin Console to indicate a disk was inserted or removed.

Requirements for Hot Plugging

• The configuration option disk.volumes must be set to all.

• JBOD/pass-through mode must be supported and enabled to use a disk with a RAID controller. Contact DataCore support for details.

• Disks must not be configured in RAID.

• Any virtual machines housing Swarm storage nodes must enable disk UUIDs (set disk.EnableUUID=TRUE). 

Guidelines for Hot Swapping

• Count the total disks (status OK) across all node processes and verify it equals the value before pulling any disks to determine if hot swapping succeeded. The disk may not be assigned to the same node process handling it before being moved.

• Expect a disk that is plugged back in to least show up in the first node process on the machine if SNMP is slow to update. The disk adds algorithm attempts to keep the volume assignments balanced across node processes.

• Check the disk identification lights: The disk identification light is automatically enabled if a disk cannot mount when hot-plugged into a system or fails at boot time.

• Expect to see "noise" in the syslog about failed volume recovery (FVR) starting when pulling a live, good disk (not retired or disabled due to error count). Look for these announcements:

  • FVR has completed or been cancelled on the hot-swapped disk.

  • The hot-swapped volumeID is mounted and recognized by the assigned node process.
    
    

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Preparing Repurposed Drives for Use in Swarm

There are two methods to prepare repurposed drives:

Method 1: Using a Linux/Unix System to Prep the Drive

1. Plug the drive you want to repurpose for Swarm use into a generic Linux/Unix system.

2. Once you are sure of the device name for the drive to be reused, issue the following command (you will need to have ‘root’ privilege for this):

   # dd if=/dev/zero of=/dev/sda bs=1k count=10000

3. Once step 2 is complete, remove the drive from the system where it was wiped and plug it into a Swarm node for use. If your hardware supports the “hot plug” of drives, Swarm will pick the drive up if properly detected and format it for use with no node restart required. If the hot plug is not supported, shut down the node, add the drive, and then start the node for it to be detected and used.

Method 2: Using a Windows System

1. Plug the drive you want to repurpose for use in Swarm into a Windows system where you have administrative privilege.

2. Open up a CMD or Powershell prompt that runs as Administrator.

3. Run the command diskpart.exe.

4. At the “DISKPART>” prompt, run “list disk” to get the list of disks attached, verifying that the one you want to modify is present:

   DISKPART> list disk Disk ### Status Size Free Dyn Gpt -------- ------------- ------- ------- --- --- Disk 0 Online 476 GB 1024 KB * Disk 1 Online 931 GB 0 B * DISKPART>

   In this example, if we want to wipe “Disk 1”, you would then issue the following command at the “DISKPART>” prompt:

5. Once the clean operation is complete, the drive can be used in your Swarm storage cluster.