633543-001 is the HPE spare part number for 2GB P-series Smart Array Flash Backed Write Cache. This is the number HPE service documentation, iLO event logs, and the label on the failed module use to identify the part, so it is the correct reference when you are replacing a cache module in the field. The module provides 2GB of RAID controller cache memory with flash backed write cache protection for P-series Smart Array controllers. Supported platforms include DL160 Gen8, DL320e Gen8, DL360e Gen8, DL360p Gen8, DL380e Gen8, DL380p Gen8, DL385p Gen8, DL560 Gen8, ML310e Gen8, ML310e Gen8 v2, ML350e Gen8, ML350p Gen8, SL4540 Gen8, and SL4545 G7.
HPE Option Part #: 631681-B21
HPE Spare Part #: 633543-001
HPE Assembly Part #: 610675-001
PRODUCT SPECIFICATIONS FOR 633543-001:
- Product Type: RAID controller cache memory
- Cache Memory Capacity: 2GB
RESOURCES FOR 633543-001 (631681-B21)
Quickspecs for 631681-B21COMPATIBLE WITH:
PROLIANT DL SERIES
PROLIANT ML SERIES
PROLIANT SL SERIES
** This list may not be complete. Contact us via Live Chat if you have any questions about compatibility.
FREQUENTLY ASKED QUESTIONS ABOUT 633543-001
What is the difference between 633543-001 and 631681-B21?
They are the same physical product under two different HPE numbering schemes. 633543-001, the number on this page, is the spare part number — the field-replaceable identifier used in service documentation and on the part label. 631681-B21 is the option number, the orderable kit used when the cache is purchased as a configurable add-on. This family also has one assembly revision, shown in the cross-reference block on this page. An assembly part number identifies the manufactured build-level unit behind the spare and option numbers.
I found 633543-001 in my iLO event log. What am I replacing?
You are replacing a 2GB P-series Smart Array Flash Backed Write Cache module. It is RAID controller cache memory with flash backed write cache protection, used with P-series Smart Array controllers in supported Gen8 and G7 platforms. The number printed on the failed module and the number cited in HPE service documentation will match 633543-001, so ordering against this spare number gives you the same module you removed.
Which servers does 633543-001 fit?
Supported platforms are the DL160 Gen8, DL320e Gen8, DL360e Gen8, DL360p Gen8, DL380e Gen8, DL380p Gen8, DL385p Gen8, DL560 Gen8, ML310e Gen8, ML310e Gen8 v2, ML350e Gen8, ML350p Gen8, SL4540 Gen8, and SL4545 G7. Fit also depends on the P-series Smart Array controller installed in the system, since the module attaches to the controller rather than directly to the server board.
Will a spare-numbered module work the same as an option kit module?
Yes. The spare and the option number describe the same 2GB flash backed write cache module. HPE assigns separate numbers to distinguish how the part is supplied — spare numbers for service replacement, option numbers for configurable orders — not to distinguish hardware. The module installs and operates identically on supported P-series Smart Array controllers regardless of which number you ordered against.
What arrives when I order against 633543-001?
A spare part number supplies the field-replaceable module itself: the 2GB P-series Smart Array Flash Backed Write Cache. Spare-numbered parts are packaged for service replacement rather than as retail option kits, so the packaging and any included documentation may differ from an option-kit purchase even though the hardware is the same. Verify the number on your removed module against 633543-001 before installing.
HPE PARTSURFER INFO FOR 633543-001 (631681-B21)
| Spare PN | Description | |
|---|---|---|
 | 633543-001 | 2GB flash backed write cache (FBWC) memory module, 72-bit wide - Part does not include the controller board or capacitor module - For use with the P420, P421, P430, P431, 822, and 830 Smart Array controllers |
| 660093-001 | Capacitor pack with 914mm (36 in) cable. For use with 512MB/1GB/2GB cache module - Provides back up power to the flash-based write cache (FBWC) memory module for up to 80 seconds in the event of a system power failure. For use with Smart Array controllers |
Last Updated: 2026-05-27
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This product is warrantied against hardware failure for a period of 1 Year from the date of purchase. Before making a purchase, please take a moment to review our return policy below.
Returns
It is the customer's responsibility to verify compatibility with their machine(s) before placing an order. If an item is ordered by mistake, it can be returned for refund, minus a 25% restocking fee, within 5 business days of receipt. The cost of freight is not refundable.
Please be aware that factory-sealed equipment can only be returned if it remains unopened.
Defective Products
If you have received a defective part and your machine is still within the HPE warranty period, please initiate a warranty exchange by visiting the HPE Enterprise Support Center. Be sure to have the serial numbers of the defective drive and your server/storage array handy.
In case your hardware becomes defective during the Global One warranty period, but the HPE warranty has expired, you can return the product to us for a working replacement. You are responsible for the shipment of returned merchandise. However, we will cover the expense of Ground /Economy shipment for the replacement item(s).
Requesting an RMA
To initiate a return or warranty claim, please complete and submit the RMA Request Form.
