Lenovo 4XB0G45727 300GB SAS 15K HDD: Array Expansion Guide
Adding drives to a server that already has an array is not the same job as building a new one, and the difference catches people out. The drives you buy have to match what is already there in ways that go beyond capacity.
The Lenovo 4XB0G45727 is a 300GB SAS 12Gb/s 15K 2.5-inch hot-swap drive, and it is most often bought to extend or repair an existing ThinkSystem or System x array rather than to fill an empty chassis.
Expanding an array versus adding a new one
There are two ways to use empty bays in a server that already has a working array, and they behave completely differently.
Extending the existing RAID group. The new drives join the current group, which then has to redistribute data across all members. This is a long operation, the array runs degraded in performance terms while it happens, and every new drive must match the existing members on capacity, interface and spindle speed. Mismatch on any of those and the group either wastes capacity or slows to the new drive’s speed.
Creating a separate RAID group. The new drives form their own group and their own volume. No redistribution, no risk to the existing data, and the new group can use different drives entirely if you want a different tier.
Most of the time the second option is both safer and more useful. Extending a group is worth it when you genuinely need one larger volume; creating a group is better when you need more storage and can live with it appearing separately.
The mistake to avoid is buying drives for an expansion without deciding which of these you are doing, because the matching requirements differ completely.
4XB0G45727 specifications
| Part Number | 4XB0G45727 |
| Manufacturer | Lenovo |
| Capacity | 300GB |
| Interface | SAS 12Gb/s |
| Rotational Speed | 15,000 RPM |
| Form Factor | 2.5 inch SFF |
| Carrier Type | Hot-Swap |
| Drive Class | Enterprise Performance |
| Condition | Refurbished, function-tested |
| Warranty | 30-day TechSellerUSA warranty |
What has to match, and what does not
A checklist worth working through before ordering drives for an existing system.
Must match: form factor. A 3.5-inch drive will not enter a 2.5-inch bay. No exceptions.
Must match: carrier generation. Lenovo and IBM used G2HS and G3HS trays plus earlier hot-swap and simple-swap designs, none interchangeable. The part number encodes this.
Must match within a RAID group: capacity. The group uses the smallest member, so a larger drive strands its excess.
Must match within a RAID group: spindle speed. The group degrades to the slowest member, so a 10K drive among 15K members slows everything.
Should match: firmware coding. ServeRAID controllers validate drive firmware; a generic drive may be flagged, may not report health telemetry, or may be refused during a rebuild.
Does not need to match: manufacturer. The underlying mechanism can come from any of the three remaining drive makers provided the specifications above line up.
SKU: 4XB0G45727  | Refurbished & function-tested  | 30-day warranty
View Details & Request a Quote →Where 300GB at 15K belongs
The capacity looks small and that is intentional. 15K drives trade capacity for latency, because a platter spinning that fast has to be smaller and the mechanical tolerances tighter.
What you buy with a 15K drive is a fast spindle, and in performance arrays spindles are the unit that matters. IOPS scale with the number of drives, not with total capacity, so sixteen 300GB drives deliver roughly four times the concurrent operations of four 1.2TB drives holding the same total.
That makes 300GB 15K drives right for transactional databases, busy virtualisation datastores, and log or index volumes where latency governs. They are wrong for anything capacity-driven, where nearline drives cost a fraction per terabyte.
Lenovo and IBM part number overlap
Lenovo acquired IBM’s x86 server business, so ThinkSystem and System x share engineering and the drive ranges overlap across the transition. A server bought as a System x may take drives listed under either brand depending on when it was configured.
Lenovo also uses more than one numbering scheme — parts beginning 4XB and parts beginning 00 both appear, sometimes for closely related products. That is a consequence of the transition rather than a meaningful distinction.
The reliable approach never changes: pull a drive currently fitted and order against its part number, which encodes drive, carrier and firmware in one string. Our compatibility guide lists Lenovo and IBM parts side by side.
Ordering
We supply the 4XB0G45727 refurbished and function-tested with a 30-day warranty, single spares or in sets for array expansion. Tell us whether you are extending an existing group or creating a new one and we will confirm what needs to match. Browse the full Lenovo range or our complete enterprise hard drives catalogue.
Common questions
Should I extend my existing RAID group or create a new one?
Creating a separate group is usually safer and simpler: no data redistribution, no risk to existing data, and the new group can use a different drive tier. Extend the existing group only when you genuinely need one larger volume.
What has to match when adding drives to an existing array?
Form factor and carrier generation absolutely, since neither has any flexibility. Within a RAID group, capacity and spindle speed must match or you waste capacity or slow the group. Firmware coding should match on OEM platforms. Manufacturer does not need to match.
Why is a 300GB 15K drive worth more than a larger nearline one?
Because you are buying a fast spindle rather than storage. IOPS scale with drive count, so sixteen 300GB drives deliver roughly four times the concurrent operations of four 1.2TB drives holding the same total capacity.
Why do Lenovo drives have two different part number formats?
Parts beginning 4XB and parts beginning 00 both appear, which is a consequence of the IBM to Lenovo transition rather than a meaningful distinction. Identify the part number from a fitted drive rather than working from the server model.
Tell us whether this is a repair or an expansion and we will confirm the matching requirements before quoting.
