MjM Data Recovery Ltd

Unix Services

ZFS Data Recovery

Recent Jobs

A recent job we did was for a large organisation that had inadvertently deleted hundreds of VDevs from a double Z-RAID 2 configuration. The customer had tried rolling back, then a disk failed during the rollback and another disk had failed some time ago, this left the system in a complete mess.

Our ZFS engineers looked at it and at first, it seemed that it was unrecoverable, but after many weeks of untangling the system finding old file system structures, determining which VDevs the parts of the file system were related to and writing several scripts we managed to extract more than 90 percent of the data on the system.

So, whatever any other data recovery company will tell you, your data is not always lost. With our advanced knowledge of how file systems like ZFS work the impossible can become reality. Needless to say that our customer was very pleased that we had recovered thousands of files where it was thought impossible.

Data recovery from all systems running ZFS

Single drive ZFS

Standalone desktop and laptops running ZFS on Hard drives and SSD.


Multiple drive Servers with ZFS and LVM systems, separate RAID controllers but drives hosted in same machine.

NAS and FreeNAS

NAS and FreeNAS devices using ZFS including z raid systems. Multiple drives in a single enclosure or computer.

SAN based systems

For large scale servers running multiple drive enclosures connected to a network using iSCSI or Fiber channel, managed from a local computer or web management interface.


A single parity based protection scheme. One drive can fail and the system will continue to function but in degraded mode.


THe RAID 6 equivalent for ZFS. Two parity drives for double drive failure protection. Two drives can fail and the system can still run in degraded mode.


Triple parity layout. Rarely used, seen sometimes on SAN systems and large RAID volumes. Three drives can fail in this type of RAID and data is still accessible in degraded mode.

Other Layouts

RAID 0, RAID 1, RAID 10, RAID 50, RAID 51, etc. Volume sets, LVM and some proprietary layouts.

Data recovery from ZFS file systems

The ZFS file system is developed by Sun Microsystems. ZFS has built-in protection for data corruption and supports data compression. It also has built-in automatic repair features, snapshots and other advanced file system management. However, when there are failures, the system will stop working. Querying using the console or terminal can help identify the failure.

If a pool is showing errors after a status command for example;

# zpool status -v
pool: tank
state: UNAVAIL
status: One or more devices are faulted in response to IO failures.

Then you know there are physical problems with the drives. If there are more than 1 failure in a RAID Z or more than two failures in a RAID-Z2 system, then rebuilding the array will not work. Forcing failed drives back is not a recommended

RAID Z Data Recovery

We are able to recover data from all ZFS systems, from data pools and all levels of RAID Z using single, double and triple parity. From single and multiple pools.

  • Corrupt data
  • Bad media failure
  • Physical media failure

If your ZFS system has crashed, contact us by phone or using the form below. Please describe the system you are using, number of drives, volume of data and storage layout that you are using. Compress and upload any log files or screenshots that may be useful.

Please fill in the form below and we will get back to you as soon as possible.

ZFS Contact form

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You may upload log files, or screenshots to us. Please compress large log files as there is a limit to what can be uploaded.
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