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RAR / Controllers and hosts / Dell PERC

PERC H310 · H710 · H730 · H740P · H755 · H965i · iDRAC · OpenManage · perccli · DDF · 64KB

Dell PERC array recovery. Broadcom underneath, Dell on top, and a dialect every PowerEdge owner learns the hard way.

Dell's PowerEdge RAID Controller is Broadcom MegaRAID silicon running Dell firmware, from the H310 and H710 in the R720 era through the H730 and H740P in the R730 and R740 to the H755 and H965i in the R750 and R760, with the H810 and H840 driving the MD1200 and MD1400 shelves. It writes DDF-format metadata to a reserved area near the end of every member, describing the virtual disk, the span layout, the stripe element size, which Dell's PERC 9 guide lists as 64KB, 128KB, 256KB, 512KB and 1MB with 64KB the default and the H330 fixed at 64KB, and each member's place and currency. It reports through iDRAC, OpenManage and perccli in words this site quotes: Virtual disk degraded and failed, Physical disk removed, Foreign configuration found, Punctured stripe, Preserved cache, Background initialization, Consistency check, Patrol read. And it offers buttons, of which Clear and Force online are the two that make a recoverable set into a reconstruction. A PERC set of two to four members is £500 + VAT upwards after the free look, fixed in writing; MD shelves from £1,250 + VAT.

Free first lookOne fixed figure in writingNo data, no bill on most jobsReturn postage paid

Rather talk it through? An engineer answers the bench line
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Power down. Label every slot before a drive comes out. Do not rebuild, do not force a drive online, do not import or clear a foreign configuration, do not initialise, and do not run chkdsk, fsck, zpool import -F or mdadm --create on the members. A rebuild reads every sector of every survivor and writes to the replacement; each of the commands writes to the drives. On images, all of them are reversible. On the originals, none of them is.

Models and versions we see.

Which level is it →
Family Models or versions Metadata, defaults and notes
PERC 8 and earlierH310, H710, H710P, H810R720 era · DDF · 64KB default
PERC 9H330, H730, H730P, H830R730 era · 64KB default; H330 64KB only
PERC 10H740P, H745, H840R740 era · NVMe-capable on some
PERC 11 and 12H755, H755N, H965i, H965eR750, R760 · tri-mode
Software RAIDS110, S130, S140, S160Windows driver RAID; metadata read from the OS

What tends to go wrong on a PERC.

Foreign configuration and ClearA replaced controller, moved drives or an expander failure make every member foreign, and the screen offers Import and Clear. Import with every member present usually works; Clear deletes the description from the drives, and the next step, creating a virtual disk, initialises them.
PuncturesDell's KB 000139251 defines a puncture as the controller restoring redundancy despite the loss of data caused by a double fault, also known as rebuild with errors, and notes that all punctures are double faults but not all double faults are punctures. The array reports Optimal with holes. Dell's cure is delete, recreate, restore; the bench images first. The puncture from the member's side is on the drive site.
Preserved cacheA virtual disk that goes offline with writes in the write-back cache leaves them pinned, and the controller waits. Discarding them to get the server up throws away the last writes the file system believes were made.
Keep Your Hard DriveDell's standard service returns the failed drive to Dell. Keep Your Hard Drive, included in ProSupport Plus and available with ProSupport, lets you keep it, and the failed drive holds the stripes a stalled rebuild never reached.

Dell PERC symptoms, and how long each gives you.

Not listed? Describe it on the form →
One drive amber; the set still upDegraded. Copy what matters, export the log, power down.Do not delay
Rebuild stalledA survivor's read errors. Power down; the first-dropped drive holds the stripes.Do not delay
Controller replaced; drives foreignThe description is on the drives. Do not clear.Do not delay
Several drives gone at onceBackplane, expander, cable or supply. The drives are usually fine.Everyday job
Cache lost or preservedWrites that never reached the drives. Do not discard yet.Do not delay
Packing it and posting it: power down, photograph the controller's screen or export its log, and write the slot number on each drive with a marker before it comes out of its carrier. Send every member of the set, including the one that failed first; it holds the stripes the rebuild never reached. Each drive travels in an anti-static bag inside its own padding, in a box with nothing able to move. Send the controller if it was replaced or holds an encryption key; otherwise it stays. Insure the parcel for what the data is worth, use a tracked service, and know that the posting address is not printed anywhere on this site; it arrives by email in reply to the form, with a booking sheet to print; the sheet inside the parcel is what matches it to your enquiry when it is opened. Or hand the sealed parcel in at the nearest of ten drop-off points, your name on the outside and the sheet inside; say where you are on the form and it comes by email. We pay the postage home either way. The whole of it is written up on the guide to packing and posting.

What the message means on a PERC.

Describe yours to us →
What you see The usual reason Where that leaves you
Punctured stripe / bad blocksRebuild with errorsImage before deleting and recreating
Preserved cache for an offline virtual diskWrites pending when the set went downDo not discard until the members are imaged
Virtual disk import failedA member missing, copies disagree, or newer firmwareDo not clear; send the set and the old controller
Virtual or logical disk degradedA member out; still readableImage the weak drives before rebuilding
Virtual or logical disk failed or offlineToo many members outEvery member imaged; set reassembled from images
Foreign configurationMetadata the controller does not claimDo not clear; import only with every member present
Predictive failure on a survivorThresholds crossedStop; image before any rebuild

From the parcel arriving to your files going back.

Work we have closed →
01

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

A case number goes on the parcel and a number on every member the day it is opened, matched to the slot you wrote on it. Each member goes on the imager its interface needs, never on a controller, and its metadata is read before a sector is: the level, the order, the stripe size, the event counts that say which member is current and which dropped out first. An engineer settles what has happened to the set and how much of it can honestly be read back. Back to you come two things together: a straight note of what is liftable and what is not, plus one figure, fixed and written down. Accept it, or decline and owe us nothing.

Nothing to pay for lookingA single figure, put in writingNo rebuilds, no imports, no initialise
02

Every member imaged, including the one that failed first

Every drive in the set is imaged sector by sector, weak areas last, on hardware that controls every retry, with a map of what could not be read kept for each. Members with failed heads go to the clean bench first; that is the drive site's work and the same bench does it. The drive that dropped out first is imaged too, because it still holds every stripe written before it dropped, and a rebuild that stalled part-way never reached them.

Sector by sector, weak areas lastThe first-dropped member included
03

The geometry, from the metadata or from the parity

Where the controller's metadata survives on the members, the order, stripe size, parity rotation and data offset are read from it. Where it was cleared or overwritten, they are recovered from the data: parity across the members at the same offset should XOR to zero on a consistent stripe, which confirms the level and finds the stale member; where parity lands says the rotation; entropy at stripe edges and the file system's own anchors give the stripe size, the order and the start.

Metadata first, parity secondOrder, stripe, rotation, offset
04

Assembled in software, and repaired on the virtual volume

The set is put together from the images in software, with nothing written to any of them: the current members in, the stale member used only to fill holes a survivor could not give. The file system is checked and repaired on a copy of the virtual volume, VMFS and CSV volumes opened and the virtual machines' disks extracted, databases repaired where they need it. The originals are not touched again.

Nothing written to the imagesVirtual machines and databases opened
05

You see the file list before you pay

What was recovered is listed for you first, and only then does a bill exist. Approve the list and it is invoiced; turn it down and it is not — and where nothing has come back, most jobs carry no charge at all. Recovered data travels home on fresh media bought in for your job, with the postage at our end. Your case is not closed until you have opened the files on a machine of your own.

No charge until you accept the figureFresh media, supplied with the job5–10 days at the bench

From the bench

  • Export the log from OpenManage, iDRAC or perccli before the server is touched. The TTYLOG records punctures and drops with timestamps.
  • The stripe element size is in the metadata, and on PERC 9 the default was 64KB. Say it if you set it; the bench reads it either way.
  • A replacement PERC on newer firmware may refuse the import. Send the old controller with the drives.
  • Export the controller log first. It is the best record of what failed when, and the bench reads it.
  • The drives are the job; the controller is context. Send it if it was replaced or holds an encryption key.
  • Keep the first-dropped drive. It holds the stripes the rebuild could not compute.

One job, followed all the way through.

UK · RAR-2026-0625JOB LOGGED ✓

An R740 with a PERC H740P, RAID 5 of six, slot 2 failed and a hot spare rebuilding onto a set whose slot 5 had been predictive for a month, the rebuild stalled at 44 per cent and the virtual disk Failed

All seven drives came in, including the part-written spare. Slot 2 had failed heads and was imaged after a head swap; slot 5 was imaged with its weak areas last; the DDF metadata gave a 64KB stripe and the order, and parity across the images proved them. The set was assembled from the four clean survivors and the slot 2 image, with slot 5's image for stripes past 44 per cent that the rebuild had never reached. The file server's volume mounted and was copied out.

100% of the volume recovered8 days here, and back by post
Illustrative example — replace with a genuine case

What helps, and what harms.

Do this much first

  • Export the log and photograph the screen
  • Power down and label every slot
  • Send every member
  • Tell us the controller, the level, the stripe size if known, and what was tried

What sets us back

  • Rebuilding with a second drive flagged
  • Clearing a foreign configuration
  • Forcing failed drives online
  • Deleting and recreating the virtual disk

Questions answered before you commit.

What does Dell mean by a punctured stripe?

In Dell's words, a feature that allows the controller to restore the redundancy of the array despite the loss of data caused by a double fault, also known as rebuild with errors. The array reports Optimal with holes in it. Image before deleting and recreating.

Should I import the foreign configuration?

If every member is present and the copies agree, usually yes. If a member is missing, a drive dropped out and came back, or the controller says import failed, no. Never clear.

What is the default stripe size on a PERC?

Dell's PERC 9 guide lists 64KB as the default, with 64KB to 1MB selectable and the H330 fixed at 64KB. The bench reads the actual value from the metadata.

Does Dell recover data from PowerEdge arrays?

Not as a service we could find. Dell withdrew its hard drive data recovery service in 2022, and it only ever covered client PCs. Keep Your Hard Drive lets you keep the failed drive; the recovery is done here.

What does it cost?

£500 + VAT upwards for a set of two to four members after the free look, fixed in writing; MD shelves and larger sets from £1,250 + VAT.

Begin here if yours is doing the same thing.

Virtual disk degraded →Foreign configuration: import or clear →Preserved cache and cache data lost →RAID 50 and RAID 60 →Broadcom MegaRAID and ServeRAID →Punctures, from the member's side →

Nothing gets worse while it is powered down.

Looking at it is free. Back comes a list of what opened and what did not, together with a single price to finish, set down in writing while you are still free to say no. On most jobs an invoice only follows the data. Until that list reaches you, leave the server off and the drives in their slots.

0800 6890668

Price my jobPacking and posting