DG Import/Export in SupremeRAID™ HE for High Availability

8/1/25

Introduction

This feature allows users to implement a basic active-standby high availability (HA) setup using SupremeRAID™ HE. To gracefully migrate services from node A to node B, users can export the Drive Group (DG) on node A, then import it on node B and resume the service. The following sections explain how this process works.

Key Concepts

Foreign PD: A physical drive (PD) containing valid Graid metadata that belongs to a different system/config UUID.
Foreign Config: Configuration metadata on a foreign PD.
Foreign DG: A Drive Group defined by a foreign config.
Foreign Hotspare: A hotspare PD described in a foreign config.

Feature Details

PD States

A new state, PDS_FOREIGN, represents PDs with foreign configurations.

Creating a PD

By default, creating a PD will not wipe its metadata. If foreign metadata is found, the PD is marked as foreign.
Use -w or --wipe-meta to explicitly erase existing metadata:

$ graidctl create pd 0 -w

PD Data Protection

To protect against concurrent writes, non-foreign PDs acquire an exclusive-write NVMe reservation if supported.
If this reservation is lost (preempted), the PD is marked as foreign.

Exporting a DG

Before migrating a DG, use the following command to cleanly take it offline:

$ graidctl export dg 0

This operation transitions all member PDs to foreign state and marks the DG as offline.

Example Output:

$ sudo graidctl export dg 0
✔ Export drive group successfully.

$ sudo graidctl ls pd
✔ List physical drive successfully.
┌───────┬───────┬──────────────┬──────────┬───────┬──────────┬─────────┬───────────┬─────────┬───────-─┐
│ PD ID │ DG ID │ DEVICE PATH  │ NQN/WWID │ MODEL │ CAPACITY │ SLOT ID │ NUMA NODE │ WEAROUT │ STATE   │
├───────┼───────┼──────────────┼──────────┼───────┼──────────┼─────────┼───────────┼─────────┼────────-┤
│ 0     │ 0     │ /dev/nvme5n1 │ uuid.01  │ NVMe  │ 932 GiB  │ N/A     │ N/A       │ N/A     │ FOREIGN │
│ 1     │ 0     │ /dev/nvme6n1 │ uuid.02  │ NVMe  │ 932 GiB  │ N/A     │ N/A       │ N/A     │ FOREIGN │
│ 2     │ 1     │ /dev/nvme7n1 │ uuid.03  │ NVMe  │ 932 GiB  │ N/A     │ N/A       │ N/A     │ FOREIGN │
│ 3     │ 1     │ /dev/nvme8n1 │ uuid.04  │ NVMe  │ 932 GiB  │ N/A     │ N/A       │ N/A     │ ONLINE  │
│ 4     │ 1     │ /dev/nvme9n1 │ uuid.05  │ NVMe  │ 932 GiB  │ N/A     │ N/A       │ N/A     │ ONLINE  │
└───────┴───────┴──────────────┴─────────-┴───────┴──────────┴─────────┴───────────┴─────────┴────────-┘

$ sudo graidctl ls dg
✔ List drive group successfully.
┌────────┬────────┬────────┬──────────┬──────────┬────────┬─────────────────────────────────┐
│ DG ID  │ MODE   │ VD NUM │ CAPACITY │ FREE     │ USED   │ STATE                           │
├────────┼────────┼────────┼──────────┼──────────┼────────┼─────────────────────────────────┤
│ 0      │ RAID5  │ 0      │ 1.8 TiB  │ 1.8 TiB  │ 0 B    │ OFFLINE                         │
│ 1      │ RAID1  │ 0      │ 931 GiB  │ 931 GiB  │ 0 B    │ INIT (0.38%, 42 mins remaining) │
└────────┴────────┴────────┴──────────┴──────────┴────────┴─────────────────────────────────┘

Scanning Foreign DGs

Use this command to detect foreign DGs available for import:

$ graidctl scan foreign_dg

Example Output:

$ sudo graidctl scan foreign_dg
✔ Scan foreign dg successfully.
┌────────────────────┬────────┬───────────────────────--┬────────────┐
│ DG UUID            │ MODE   │ PD                      │ IMPORTABLE │
├────────────────────┼────────┼───────────────────────--┼────────────┤
│ 438184443912393153 │ RAID5  │ uuid.01 (PD0: foreign)  │ Yes        │
│                    │        │ uuid.02 (PD1: foreign)  │            │
│ 438184488854358273 │ RAID1  │ uuid.03 (PD2: foreign)  │ No         │
│                    │        │ uuid.04 (PD3: foreign)  │            │
│                    │        │ uuid.05 (PD-1: unknown) │            │
└────────────────────┴────────┴─────────────────────────┴────────────┘

Info

uuid.05 does not exist or has not been created as a PD.

A DG is not importable if:

One or more VDs are used in stripe-cache
One or more VDs are exported via NVMe-oF
A local active DG has the same UUID
Any PD is not created or belongs to another config/DG
Any PD is already part of a local DG

Importing a Foreign DG

Use the following command to import a detected foreign DG:

$ graidctl import foreign_dg 6bb660be-6b8d-4a50-a151-4c55b3cbe413

Example Output:

$ sudo ./gtl import foreign_dg 438184443912393153
✔ Import foreign dg successfully.

$ sudo ./gtl ls dg
✔ List drive group successfully.
┌────────┬────────┬────────┬────────────┬────────────┬────────────┬────────────────────────────────────────────────┐
│ DG ID  │ MODE   │ VD NUM │ CAPACITY   │ FREE       │ USED       │ STATE                                          │
├────────┼────────┼────────┼────────────┼────────────┼────────────┼────────────────────────────────────────────────┤
│ 0      │ RAID5  │ 0      │ 1.8 TiB    │ 1.8 TiB    │ 0 B        │ INIT (58.06%, 24 mins remaining)               │
└────────┴────────┴────────┴────────────┴────────────┴────────────┴────────────────────────────────────────────────┘

Foreign Hotspare Management

To export and import global hotspares:

Export a hotspare PD:
```
$ graidctl export hotspare 2
```
Scan for available foreign hotspares:
```
$ graidctl scan foreign_hotspare
```

Import a hotspare:

$ graidctl import foreign_hotspare 1cb70a2b-4e38-4ff2-abc7-f7b830e50835