Supermicro 815 1U case 2,5″ HDD and RAID card battery holder (#P40)

New year, new hardware. Given space (in general, as well as in this specific case) is limited, old hardware has to go. So it’s about time post this 3D printed thingy, since the related hardware is about to be sold.

Now, the Supermicro 815 case, CSE815, SC815 or whatever prefix is en vogue nowadays, is one of those 1U pizza boxes. Shout-out to Supermicro for using webp images on their website already – but sticking to 261 x 222 px resolution for the full-size file.

Anyway, these come in two dozen varieties plus the EOL ones, and all of them have four 3.5″ HDD hotplug caddies in the front and some 1 to 3 card slots in the back, since it is a tiny case at 1U or 44mm height regardless of the 19″ width. Other 800 series chassis offer 8x 2.5″ drives. Sacrificing one (or two) of those slots for the OS disk isn’t that big of a deal, but at four slots total, it sometimes is. Note that these chassis predate NVMe disks, just putting one of these on a compatible board is great, or adding them onto the low profile PCIe riser is another option. Heck, even using some onboard USB for Linux boot drives is possible, but sometimes you do want a good ol’ SATA or SAS 2.5″ disk for your operating system. In let’s say the 836 cases with suitable backplanes it is easy to add in another disk, e.g. shown in #P23

it’s not always that easy in tight 1U cases, even if the backplane offers power connectors for such a mod.

Here’s my proposal: Print this holder, remove the mainboard, sandwich the print in between case and board, and screw it back in!

This idea came about with another mounting-related issue in the 815 case, which isn’t a fault of the chassis (any chassis) per se, but more one of the RAID card. Those pizza boxes were equipped with a “real” RAID card that is difficult to convert to an HBA that just provides the interface without any magic layers between OS and disk. Model number MegaRAID 9271-4i, SAS2208 chipset. These have separate batteries (backup battery units – BBUs – type BAT1S1P in this case) to hold data in the event of power loss, which is reasonable given my 815 variant does not have a redundant power supply (but many do). While that is great and can save your hardware RAID (for those ZFS agnostics), the card itself has no mounting points for the BBU. The server was literally shipped like this:

The chunk connected to the thick black cable near the bottom is the BBU – “Flapping around in the breeze”, as Dave Jones likes to say. Able to move any direction while shipping, and less so after installation in the rack. It doesn’t even have like a proper mounting system, it’s sitting flat when upside-down as in that photo (but has no mounting holes underneath, and the chassis is too thin for that anyway), and it sits lopsided on the other side and has awful M2.5 protruding screw holes – three of them, for extra instability.

So combining the need for a 2.5″ HDD mount and something to hold the darn BBU, the print just got a little bigger and now looks like this:

Note the outer shape has a couple of constraints, such as ATX mounting points for the board, protruding solder joints such as from the DIMM slots, chassis edge, ribbing between board and disk part of the chassis and also typical length of PCIe cards, plus the bending radius of all cables.

The small bridge parts then enclose both disk and BBU, and get screwed down on both sides with slightly longer UNC 6-32 screws than usual. M3 would do as well, but has finer threading, so I actually prefer the UNC in printed parts without metal threaded inserts.

Everything is accessible from the top without the annoying removal of the board, which I didn’t incorporate into the design in the first revision :oops:

The fully populated unit looks like this:

(a lower bridge or 2.5mm of immovable padding is needed for 7mm drives instead of the old 9.5mm ones!)

While it still isn’t fixed near the chassis edge, there’s plenty of PLA material to stiffen the entire assembly and keep in in place. Job done – BBU is secured, there’s an additional spot for a 2.5″ hard disk, and the entire mod is removable from the chassis and leaves no marks behind.

Print files:
Original RSDOC file (4 parts)


Dual unit, HDD only, Bridge part for 2.5″, Bridge part for BAT1S1P

And also hosted on thingiverse again – glad their renderer is now working again.

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