Apple GALXP 750GB Drive Module: Xserve RAID Identification Guide
GALXP is a part designation that sends a lot of people down the wrong path, because it looks like a Dell or HPE code and is neither. It is an Apple part — it appears on 750GB Ultra-ATA drive modules built for the Xserve RAID, and it is listed across the enterprise parts market alongside the Apple number 655T0224.
This guide explains what a GALXP drive module is, why Apple's storage used a proprietary carrier at all, how to tell an Xserve RAID module apart from the superficially similar Xserve server modules, and what to do if you are still keeping one of these arrays alive.
What GALXP identifies
Secondary-market listings consistently describe GALXP, also written GALXP655T0224, as a 750GB 7,200 RPM Ultra-ATA drive kit for the Apple Xserve. The mechanism inside is a Seagate Barracuda — listings pair it with the model ST3750640NA, where the NA suffix denotes an Apple OEM variant — mounted into an Apple Drive Module carrier. You will also see related Apple numbers such as 655-1351A, 620-3084 and 661-4260 on equivalent 750GB Xserve RAID drive assemblies.
Because these are reseller and secondary-market records rather than a current Apple catalogue, treat the exact number pairings as a strong indication rather than gospel, and confirm the physical carrier against the array you are fitting it to. Apple retired this product line years ago and the documentation has largely gone with it.
Why Apple used a proprietary drive module
The Xserve RAID was Apple's rack storage array, introduced in February 2003 and discontinued in February 2008. It held 14 independent ATA100 drive bays, connected to hosts over Fibre Channel — 2 Gb SFP on the later models, giving 200 MB/s of throughput — and supported hardware RAID 0, 0+1, 1, 3 and 5, with hybrid levels like 10 and 50 assembled in software. Filled with 750GB modules, the array reached 10.5 TB.
Each drive got its own channel. That is the design decision that explains the whole product. Parallel ATA is a shared-bus interface, and putting two drives on one channel means they contend. Apple gave each of the 14 bays a dedicated ATA100 channel, which removed the contention but required a carrier that carried the channel electronics as well as the drive.
The Apple Drive Module is not just a caddy. Unlike a plain sled that only holds a drive against a backplane connector, the ADM is a carrier assembly matched to Apple's controller. This is why a bare 750GB PATA drive does not simply drop into an Xserve RAID bay, and why the modules trade as complete assemblies rather than as drives and caddies separately.
The trade-off Apple accepted — cheap high-capacity PATA mechanisms at a time when equivalent SCSI and Fibre Channel drives cost several times as much — made the Xserve RAID unusually cost-effective per terabyte for its era. It also tied its owners to a carrier that nobody else made. Our guide on server backplanes, caddies and bay blanks covers how this pattern repeats across vendors.
Xserve RAID modules vs Xserve server modules
This is the single most common sourcing mistake with these parts, and it is worth getting right before you spend money.
Check the interface, not the capacity. Apple shipped 750GB drive modules for both the Xserve RAID array and the Xserve server itself, and they are not the same part. The Xserve RAID used Ultra-ATA. The Xserve servers of the equivalent era used Serial ATA, and the later Intel Xserve generations moved to SATA and SAS modules again with different carriers. A listing that says "750GB Apple Drive Module for Xserve" without naming the interface is ambiguous, and half the time it is the wrong one for whichever machine you have.
Ultra-ATA, PATA and IDE all mean the same thing here. If the listing says any of those, it is an Xserve RAID module. If it says Serial ATA or SATA, it is not.
The connector is the final check. A parallel ATA drive carries the wide 40-pin data header and a separate 4-pin Molex power connector. A SATA drive carries two narrow L-shaped connectors. If you can see a photograph of the back of the module, you can settle the question in a second.
Keeping an Xserve RAID running in 2026
If you are reading this because you still have one in service, the honest answer is that the array is 18 years past introduction and the mechanisms inside it are consumer-class PATA drives of similar age. There is no supply of new-old-stock left in any meaningful quantity, and drives that have sat unpowered for a decade fail on spin-up at a rate that surprises people.
If it holds data you need, it is not backed up by being in RAID. A 14-bay RAID 5 array of contemporaneous PATA drives is a set of correlated failures waiting to happen, and rebuild times on PATA at this capacity are long enough that a second failure during rebuild is a realistic outcome, not a theoretical one. Our guide on the 3-2-1 backup rule and why RAID is not backup makes the case at length.
Plan the migration rather than the repair. Fibre Channel at 2 Gb, ATA100 mechanisms and a controller with no firmware support are three independent reasons the platform will not carry another five years. Our guide on storage migration planning covers sequencing a move off a legacy array, and building a spares strategy for end-of-life hardware covers how to hold it together while you do.
If the data is archival, get it off the array and onto something readable. Copying to modern disk or to LTO is cheap next to the cost of discovering in five years that nothing will read the volume. See LTO tape backup and keeping legacy platforms running for the practical side.
If you are buying one anyway
Sometimes there is no choice — a single failed module in an otherwise working array, or a forensic or archival need to read specific media. In that case:
Buy more than one. The failure rate on decade-old unpowered PATA drives makes a single spare an optimistic purchase.
Ask for a power-on test and SMART output. Power-on hours and reallocated sector count tell you what you are getting. Our guide on reading drive health data covers which attributes matter.
Confirm the carrier is included and undamaged. A bare drive without the ADM carrier is not usable in the array, and the carriers are harder to find than the drives.
Sourcing
We source legacy and current enterprise storage, including hard-to-find drives and carriers for discontinued platforms, and we can advise on migration targets when a legacy array is no longer worth feeding. If you are identifying an Apple drive module, matching a part to an Xserve or Xserve RAID, or planning a move off a legacy array, send us the part number or the system model. Request a bulk quote or email sarah.jane@techsellerusa.com.
Common questions
What is a GALXP drive?
GALXP, also written GALXP655T0224, is an Apple part designation appearing on 750GB 7,200 RPM Ultra-ATA drive modules for the Xserve. The mechanism inside is a Seagate Barracuda — listings pair it with ST3750640NA, an Apple OEM variant — mounted in an Apple Drive Module carrier. It is not a Dell or HPE part, despite the format of the code.
Can I put a standard 750GB PATA drive in an Xserve RAID?
Not without the Apple Drive Module carrier. The ADM is a carrier assembly matched to Apple's controller rather than a plain sled, which is why these modules trade as complete assemblies. If you have a spare carrier from a dead module, transferring a compatible mechanism into it is a known approach, but a bare drive will not go into an empty bay on its own.
How do I tell an Xserve RAID module from an Xserve server module?
By the interface, not the capacity. The Xserve RAID array used Ultra-ATA, also called PATA or IDE. The Xserve servers used Serial ATA, and later Intel generations used SATA and SAS with different carriers again. Apple shipped 750GB modules for both, so a listing that only says "750GB Apple Drive Module for Xserve" is ambiguous. The physical giveaway is the connector: PATA has a wide 40-pin header plus a 4-pin Molex; SATA has two narrow L-shaped connectors.
What was the Xserve RAID?
Apple's rack-mount storage array, introduced in February 2003 and discontinued in February 2008. It carried 14 independent ATA100 drive bays, each on its own channel, connected to hosts over Fibre Channel — 2 Gb SFP with 200 MB/s throughput on later models — and supported hardware RAID 0, 0+1, 1, 3 and 5, with RAID 10 and 50 built in software. With 750GB modules it reached 10.5 TB.
Is it worth keeping an Xserve RAID in service?
Rarely. The platform was discontinued in 2008, the mechanisms are consumer-class PATA drives of the same vintage, there is effectively no new stock, and drives stored unpowered for years fail on spin-up more often than people expect. A 14-bay RAID 5 array of same-age drives carries a real risk of a second failure during a rebuild. If the data matters, get it copied off and plan a migration rather than buying spares indefinitely.
What other part numbers appear on these modules?
Equivalent 750GB Xserve RAID drive assemblies appear in the secondary market under Apple numbers including 655T0224, 655-1351A, 620-3084 and 661-4260. Apple used separate number series for the assembly, the service part and the module, which is why one physical item carries several. Search on more than one of them, because stock listed under one number will not appear under another.
If you are identifying an Apple drive module or planning a move off a legacy array, send us the part number and we will tell you what it is and what your options are.
