iSCSI LUN recovery

A missing iSCSI LUN must be recovered through both the NAS storage layer and the block device it presented.

An iSCSI target exposes block storage from a NAS or SAN to a server. The LUN may be file-backed, volume-backed, thin-provisioned, snapshot-based, encrypted, or protected by RAID, so loss can occur at several layers before the guest filesystem is considered.

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Understand the symptom

Target availability does not prove the underlying block map is intact.

WHY

What is happening

The iSCSI target, LUN mapping, backing store, RAID pool, snapshots, and client filesystem each have separate metadata. A server may reconnect to a wrong or empty LUN after recreation, while a thin LUN can reference extents across a larger pool. Recovery must establish the original backing object and host write history.

What you may see

Symptoms that change the recovery path.

Target connects but LUN is absent

Discovery works while the expected mapping or backing object is missing.

LUN appears as RAW or uninitialized

The client sees blocks but not the original partition or filesystem.

Capacity changed or reports zero

Target metadata or thin-provisioning maps are incomplete.

VMs or databases stopped after NAS failure

Guest applications depended on the LUN's block order and consistency.

Protect the source

Actions that can make the situation worse.

Recreating a LUN writes new maps

Matching the old size does not recreate the original extent allocation.

Client repair changes shared blocks

CHKDSK, fsck, or LVM activation can write through iSCSI to the source.

Snapshots can be deleted during cleanup

A useful pre-incident state may be lost with routine storage maintenance.

Do this now

Safe steps before evaluation.

Disconnect write access

Stop initiators, clusters, VMs, databases, and multipath clients from mounting the LUN.

Export target configuration

Save IQN, LUN IDs, backing paths, capacity, thin settings, CHAP, snapshots, and mappings.

Preserve NAS and pool state

Keep all disks, cache, controllers, encryption keys, and event logs.

Record client context

Document partitions, LVM, filesystems, VM datastores, cluster ownership, and last successful mount.

NEPFOSYS process

How a data-first evaluation proceeds.

Layered topology review

NEPFOSYS maps target, LUN, backing store, pool, RAID, and client filesystem.

Source preservation

Member disks or backing files are acquired before reconstruction.

Virtual LUN validation

The block device is rebuilt from protected copies and priority applications are checked.

A clear next step

Preserve the original device before another repair or recovery attempt.

Start a case with the exact symptoms, incident timeline, prior attempts, encryption details, and the files that matter most. NEPFOSYS will route the case to the appropriate DFW intake or nationwide mail-in path.

Start with a case review

Questions, answered

What customers ask before starting.

Can I create a new LUN with the same size?

No. Size does not restore the original block mapping and creation writes new metadata.

Why stop the initiator server?

Client filesystems and applications can write repairs, journals, or cluster metadata back to the source.

Do snapshots help?

They may preserve a useful state, but only if their backing extents and metadata remain intact. Do not delete them during troubleshooting.

DFW local · Nationwide mail-in

Protect the device. Start with the facts.

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