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ADR / The hardware we handle / Multi-disk sets and servers

Devices · arrays, NAS and servers

RAID data recovery, London. A member fails without a sound. The silence is the expensive part.

Always remove the server from mains power prior to doing anything. First faults will rarely lead to loss of the array; it’s typically how you respond to the fault that does it: starting a rebuild which requires one completely error-free pass from beginning to end from a member that is already worn; placing a rejected drive back into the original bay from where it was removed; attempting to shuffle drives amongst various bays in the hope that things will improve. Mirrors make their owners feel good about themselves too, but when two disks are purchased together within the same packaging, fitted on the same afternoon and have performed identically ever since, they will run out of hours at roughly the same point. These disks will typically come from either a Harley Street medical facility whose imaging was stored on a single NAS located in their basement, or a Mayfair company consisting of fewer than fifty employees who do not have sufficient space for a server room. Array and server work begins at £500 + VAT, there is no cost associated with the diagnosis that sets the figure, and nothing will continue to degrade here, as we perform all operations on images.

Only pay if we recover your data, on most jobs A free look first, then one figure in writing Media posted in from Croydon, Ealing and Camden

Put it to an engineer — the first look costs nothing
0203 0868633

RAID symptoms, and how long each gives you.

Not listed? Try the finder →
A second disk failed part-way through the rebuildThis is how most RAID 5 arrays go down. All remaining disks need to read clean from end to end, and the weakest disk is unable to.Do not delay
The controller has marked it offline or foreignThere is almost always some sort of confusion on the card, with sound drives sitting behind it.Everyday job
RAID 5 with two members downThat is one more than parity allows for. Working patiently at the sector level still returns the majority of the data.Do not delay
The rejected disk has gone back into its bayDo not go any further than this point. Any additional writes remove material that a clean assembly would have needed.Do not delay
The server has not come up since the power cutWrites left half-done, and a cache that emptied when the mains went out. The layout itself is still on the disks.Everyday job
Packing it and posting it: get a quote first by phone or with the form, then carefully pack it (so nothing inside shifts) and send it tracked and insured to our Guildford intake lab, or drop it off there yourself, Monday to Friday, 9am to 5:30pm (no appointment needed). We will pay for the postage to return it home. If you would like an engineer to go through the packing with you first, ring us before you seal it. For complete details on this please see the guide to packing and posting.

Brand by brand, and what tends to go wrong.

Dell's PERC rangeDell's own badge on LSI and Broadcom silicon, standard fit across PowerEdge servers, writing DDF metadata to all disks in the set.
Smart Array cards from HPEP-series cards in ProLiant chassis: RIS metadata written to the members; parity held on one disk for a run of stripes before rotating; tools normally used to access data misinterpret both.
Broadcom, LSI, Adaptec cardsMegaRAID and Microchip silicon: what Supermicro chassis and built-to-order servers usually carry.
Sets with no card at allSoftware sets: Linux mdadm, Windows Storage Spaces. There is no card here which can fail, yet once a member drops out the work at the bench does not change in the least.

What the RAID controller's message actually means.

Describe yours to us →
What is going onThe usual reason for itWhere that leaves you
A Dell PERC reporting Foreign Configuration FoundDisks describe a set the controller cannot placeAnswer nothing. Image the entire set first.
HP console, 1786: Drive Array Recovery NeededParity cover has gone, with a rebuild queued or running halfway throughOff power completely before imaging the entire set.
On an HP: 1784, Drive Array Drive FailureA member of the set has failedReplacing a disk will not fix the problem
HP, 1788: Drive Array Reports Incorrect Drive ReplacementSomeone has refitted the disks out of sequence.Bay order decides everything. Stop now.
Virtual Drive: Degraded, or OfflineParity is gone, or the volume is also goneCompletely shut down the server
On an HP: 1720, SMART drive detects imminent failureThe drive is still online, but reported as having imminent failureImage the disk the same day

From the box arriving to your files going back.

Work we have closed →
01

Logged the day it lands, and the first look costs nothing Free

As soon as your parcel arrives here, an engineer assigns a case number that same day, prior to determining what has really failed, which is the first thing done and costs you nothing. In addition to a note of what can and cannot be recovered from your drive, you will receive at the same time the fixed, written price for restoring what can be recovered. You can accept this quote, or decline it, which will result in no further obligation on your part and nothing owed to us.

Nothing to pay for lookingA single figure, put in writingNothing owed at this stage
02

A copy of every member

Hardware designed for failing disks will make a copy of each disk (including the ones that were rejected). All subsequent actions take place on these images. No data will ever be written back to a disk that you sent.

Each member cloned on its ownMembers the controller had dropped included
03

The set goes together in software

There are three pieces of information that are available from the metadata of each of the disks: what position each disk sat in, how large each stripe is, and which direction parity rotates. These items are then used to build a virtual assembly of your array using software on our own equipment, based upon the images. The original controller is never involved in this process, and no disk is ever required to perform a rebuild.

Running order recoveredYour card stays out of it
04

Then all that sits above

Once we have the virtual assembly, we repair the file system on that image (not on any of your actual disks), and open each of the VM containers and databases individually. You compare the list of contents against what you had expected to see there, and we do not send anything until you have.

VM and database stores openedVerified before anything ships
05

You see the file list before you pay

You will see what has been recovered as a list first, after which a bill exists. Accepting the list means that a bill will be issued. Rejecting the list means that a bill will not be issued, and in most cases you only pay if we recover your data. The recovered data travels from here back to you via new media purchased specifically for your project, with the cost of postage paid by us. Your case is not resolved (i.e., "closed") until you personally view the files on a computer of your own.

No charge until you accept the figureFresh media, supplied with the jobThe post home is ours

What arrives most often

  • Do not touch two things: Import and Clear. When Import is used it takes an old member's account of the set and writes it over the top of every single stripe that was good. Clear will remove the layout from every disk in the entire set; neither of these operations can be reversed. There is no reason to do either operation as long as no copies exist.
  • ProLiants don't work like textbooks tell you they should. Every disk in a set gets Reserved Information Sectors, and parity remains on one disk for a set run of stripes, usually sixteen, before switching to another disk, an arrangement called delayed parity. If you put your data through an ordinary RAID 5 utility, the output is completely nonsensical.
  • If a controller fails, that doesn't mean the array has failed. The layout exists on every single drive, which is why a controller going belly-up alarms people much more than it should. Parity rotation, stripe width and running order: everything reads back from the drives.
  • The second failure is very costly. A rebuild requests a clean read from every surviving disk from start to finish. It requests clean readings from the marginal disk too, and that is exactly the one that can't provide them.

Why single parity ran out of headroom: SATA disks provided for consumers are specified at one unreadable sector in 1014 bits. This amounts to about one bad sector per 12.5TB of reading. Rebuilding a large set that uses only one parity disk requires multiple times that amount of clean reading from every remaining disk, in a continuous read cycle, and that is where the rebuild will stop. The number provided above is based on specifications developed by manufacturers. How closely actual disks match their specification is still debated.

One job, followed all the way through.

LDN · ADR-2026-3298JOB LOGGED ✓

A second member dropped out mid-rebuild; Monday's shift still started on time

The rebuild was half-complete on the Friday when another member became unavailable, and the live volume would not mount at all. It was powered down immediately and left alone. We copied all four disks onto our storage. Three of these copies yielded good data, and the striped array was rebuilt using those plus whatever data was still available from the fourth disk. The firm's Monday shift opened as usual.

100% of the live volume back1 weekend of work

What helps, and what harms.

Do this much first

  • Shut down the server and turn off the power
  • Each time you remove a disk, assign it a number corresponding to its bay location
  • Call us for a quote or fill in the quote request form, then post all of your disks, including those that were reported as "failed", or drop them off at our Guildford intake lab, Monday to Friday, 9am to 5:30pm (no appointment needed)
  • The type of expansion card used and the type of RAID configuration, if you know them

What sets us back

  • Attempting to begin rebuilding a RAID set while leaving out one member of the set
  • Reinserting a previously rejected disk into the RAID set
  • Choosing "repair" or "initialise" from the controller menu
  • Using recovery software on a RAID set while it remains powered on

Questions answered before you commit.

Our card has thrown one disk out of the set. Send that one too?

Yes, please send it. Get a quote first, via a phone call or using the form provided. Once you receive your quotation, package up your failed disk along with the other disks and post them to our Guildford intake lab, or drop them all off there, Monday to Friday, 9am to 5:30pm. There is no need to schedule an appointment. The failed disk can still contain the most recent copy of certain stripes and therefore should accompany the other disks. When recovery begins, each block will be retrieved from whatever disk presents it most cleanly.

No one wrote down the bay each disk sat in. How bad is that?

It really isn't too bad. Your disks contain information regarding running sequence, stripe size and direction of parity rotation, so instead of guessing when trying to recover them, it becomes an analytical process. Number the disks anyway whenever possible: the time this will save you is a good hour.

Are the virtual machines recoverable too, or just the files?

Both. Once the set is standing again, all disk images (VHDX/VMDK), along with the databases, will be made available. Each one will then be mounted and opened in turn, as a name in a file listing does not provide information about the condition of the data stored inside the container.

The business has stopped until this is back. How long is it?

In the event there are multiple disks being processed, we would expect to take anywhere from four to seven working days to complete. If trading has truly ceased, please let us know. Your position in the queue will be moved forward, and we will plan accordingly around the date you have to meet. We can advise on getting the disks to us; however, we do not collect. Simply post them to our Guildford intake lab, or drop them off there, Monday to Friday, 9am to 5:30pm. No appointment is required.

Begin here if yours is doing the same thing.

Disks taken out of a NAS box → When a RAID 5 rebuild fails → Servers that refuse to come up → Begin with the symptom →

Nothing gets worse while the power is off.

It doesn't cost you anything for us to look at it. All we do is give you a breakdown of what opened and what did not, plus a single fixed price to complete, written down before you agree to let us continue. On most jobs, you only pay if we recover your data. Please don't turn on the drive until you get that breakdown.

0203 0868633

Get it assessed Sending it to Guildford