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RDD / Every kind of member drive / NL-SAS 3.5-inch

Exos X SAS · HUH721212AL5200 · MG09SCA18TE · MD1400 · D2600 · DS4246

NL-SAS 3.5-inch drives. A nearline drive is a SATA drive with a SAS board and a longer memory for its faults.

Nearline SAS puts the mechanics of a 7,200rpm capacity drive behind a SAS interface, so that a Dell MD1400, an HPE D2600, a NetApp DS4246 or an EMC DAE can fill its shelves with 4 to 24TB drives that speak the same SCSI as the fast ones. The strings tell you: Seagate's Exos SAS versions, HGST and WD's HUH and WUH strings ending AL5 or AL4, Toshiba's MG with an S. They fail the way big drives fail, at the heads and through a grown defect list that climbs for months before the controller loses patience, and they bring three complications the desktop world does not: most of them are self-encrypting, many are 4Kn rather than 512e, and the ones from NetApp and EMC use 520 or 528 bytes in every sector. One failed member imaged for the rebuild is £300 + VAT after the free look, fixed in writing, 3–4 days at the bench.

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
0800 6890668

Power down. Label every slot before a drive comes out. Do not rebuild while a second drive is flagged. Do not clear or import a foreign configuration. Do not initialise, reformat or PSID-revert anything. A rebuild reads every sector of every surviving member, and on a set whose drives were bought together it is where the second failure is found. Nothing on the drives gets worse while the server is off.

NL-SAS symptoms, and how long each gives you.

Not listed? Describe it on the form →
Predictive failure, then droppedThe grown defect list crossed the line. Readable on the bench, slowly.Everyday job
Clicking in the shelfFailed heads. Power down.Do not delay
Shows 0 GB, or incompatible sector size, on another hostA 520-byte or 4Kn drive on the wrong host. Not dead; do not reformat.Do not delay
Locked after a controller swapA SED whose key stayed on the old controller. Find the key.Do not delay
Two drives in the shelf gone in a monthSame batch. Send both; expect a third.Do not delay
Rebuild stalled at n per centA survivor's unrecoverable read errors. Power down.Do not delay
Packing it and posting it: power the server or shelf down, write the slot number on each drive with a marker before it comes out of its carrier, and keep it in the carrier. Send every member from the set where the set is the job, or the one failed member where the set is healthy and you want it imaged for the rebuild. Each drive travels in an anti-static bag inside its own padding, in a box with nothing able to move. Send the controller only if we ask for it. Insure the parcel for what the data is worth rather than the price of the drives, and use a tracked service. 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.

Where it lives, and what fails.

The grown defect listA SAS drive keeps a list of sectors it has retired, and the controller watches it. When it grows past the threshold the drive is flagged predictive, and when a read times out the drive is dropped. On the bench the list says where to read last.
520 and 528 bytes a sectorNetApp, EMC, Sun and IBM storage format their drives with eight or sixteen extra bytes per sector for checksums and protection information. A standard host refuses them. They are imaged at native size and the extra bytes stripped from the image.
4Kn and 512eThe same model arrives in both formats, told apart by the last characters of the string. A 4Kn drive in a host expecting 512-byte sectors reports the wrong capacity or none; it is not a fault.
SED, ISE and FIPSMost nearline SAS drives are self-encrypting. Instant Secure Erase discards the key on command; FIPS versions add tamper evidence. All of them are readable with the key and none without it.

Model strings, and what they tell us.

Describe yours to us →
Model string What it is What it means on the bench
ST16000NM002JExos X18 16TB SAS, self-encryptingHelium; unlock with the controller's key
HUH721212AL5200Ultrastar DC HC520 12TB SAS 512e52 = SAS 512e; 42 would be 4Kn
HUH721212AL4204Ultrastar DC HC520 12TB SAS 4KnReports the wrong capacity on a 512-byte host
MG09SCA18TEToshiba MG09 18TB SASS = SAS; A = SATA
X-series NetApp / EMC part numbersThe same drives at 520 or 528 bytes a sectorImaged at native size; never reformatted

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 drive the day it is opened, matched to the slot you wrote on it. An engineer settles what has actually happened before anything spins: the interface, the sector format, the firmware, the security state, and what the controller was saying when it stopped. 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 resets
02

The drive on its own bench

A member drive is read on the equipment its interface needs: a SAS imager for SAS and NL-SAS, a SATA imager for enterprise SATA, a terminated SCSI or Fibre Channel controller for the legacy drives, a PCIe adaptor for NVMe. It is never put back in a server, and never in a controller that will try to rebuild. Drives that answer at full speed are imaged; drives with weak or failed heads go to the clean bench, where matched donors are fitted and the service area repaired before a sector is read.

Read at its native interfaceFailing heads to the clean bench
03

Imaged once, at its native sector size

Every drive is imaged sector by sector, head by head where it needs it, with the bad areas last. Drives with 520- or 528-byte sectors are imaged as they are and the extra bytes stripped from the image, never the drive. Self-encrypting drives are unlocked on the imager with the key you supply. From then on the originals are not touched again.

Head by head, weak areas lastNative sector size preserved
04

The image, and the set

Where the set is healthy and one member was the job, the image goes back to you on a fresh drive, sector-identical, ready to rebuild from. Where the set is the job, every member is imaged and the array reassembled in software from the images: order, chunk size, parity rotation and the reshape point read from the drives' own metadata, the file system repaired on the virtual volume, never on the originals. The array work is covered in full on our RAID array site, and it happens on the same bench.

One member: a sector-identical image on fresh mediaA set: reassembled in software from the images
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 job3–4 days at the bench

What arrives most often

  • Do not reformat the sector size. The one command that makes a 520-byte drive readable on a PC is the one that erases it.
  • Find the key before you post. A SED that left its controller behind is a drive full of noise until the key arrives.
  • The model string decides the format, and the format decides the host. Copy it from the label, not from the controller.
  • Shelves fail in batches. Twelve drives bought together are twelve drives ageing together; when one goes, the second is close.

One job, followed all the way through.

UK · RDD-2026-0556JOB LOGGED ✓

Twelve HUH721212AL5200 drives from a Dell MD1400 in RAID 60, one failed and one predictive, feeding a file server nobody had backed up

The owner powered the shelf down when the second drive was flagged. Both weak drives were imaged on the SAS imager, the failed one after a head swap on the clean bench, and both images went back on fresh drives with the set's SED keys intact. The array rebuilt from twelve readable members.

100% of both members recovered6 days here, and back by post
Illustrative example — replace with a genuine case

What helps, and what harms.

Do this much first

  • Power down the shelf and label every slot
  • Copy the full model string from each label
  • Send the weak drives in their carriers
  • Find the SED key or the controller it came from

What sets us back

  • Rebuilding with a predictive-failure survivor
  • Reformatting a 520-byte drive to make it readable
  • Clearing the foreign configuration after a controller swap
  • Putting the drive in a NAS to see

Questions answered before you commit.

My NL-SAS drive shows 0 GB on another server. Is it dead?

Probably not. It is a 520-byte or 4Kn drive on a host that expects 512-byte sectors. It is imaged at its native size and the image translated. Do not reformat it.

The drive is locked after we swapped the controller. Can you unlock it?

With the key from the old controller or its key manager, yes. Without it, no; nobody can.

Can you image one drive from a shelf so the array can rebuild?

Yes, for £300 + VAT, onto fresh media, sector-identical.

What does it cost?

£300 + VAT per member after the free look; two to four from £500 + VAT; shelves and larger sets from £1,250 + VAT.

How long does it take?

3–4 days at the bench for one drive; 5–10 days at the bench for a set.

Begin here if yours is doing the same thing.

520-byte and T10 PI drives →Self-encrypting drives →Drive shows 0 GB →WD / HGST Ultrastar →Storage shelves →

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