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My HP Proliant ML110 G7 has a full-size SD slot on the motherboard. What is its use case?

The PDF manual mentions it on page 10: item 17 just to show its placement, but nothing more. In a later revision (Gen 9), it is said the slot is not hot-pluggable.

HP Proliant ML110 G7-motherboard

The motherboard also has a USB slot (item 11).

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    Some system even offer adual sdcard slot to make a mirror of them for your system
    – yagmoth555 ♦
    Jan 3, 2017 at 1:57
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    I have several dell R610 servers that have 1 Gbyte of flash on the mainboard, and no hard drives/no backplane. Had they been built with a SD slot I could have upgraded the card and continued using them, instead of parking them in the spare parts store.
    – Criggie
    Jan 4, 2017 at 6:16
  • But you can use them: boot off from USB/PXE, mount a NFS/iSCSI share and you are done...
    – shodanshok
    Jan 11, 2017 at 8:36

4 Answers 4

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It's for booting a hypervisor or lightweight operating system like VMware ESXi.

See: What happens when the USB key or SD card I've installed VMware ESXi on fails?

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  • That explains the "not hot-swappable" warnings on HP Gen8 spec sheets!
    – Kristen Waite
    May 14, 2018 at 13:30
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By installing an embedded hypervisor/OS on the SD card, you leave all the front-bay disks available for data storage. This is an useful logical and practical separation.

Some servers have two RAID1-ed SD slots: if a single SD fails, the system continue to run from the mirror, leaving you the time to replace the failed SD.

The most widely installed embedded hypervisor probably is ESXi, with a footprint less than 2 GB.

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  • My motherboard has also a USB slot. I doubt they can be raid-ed though.
    – FarO
    Jan 3, 2017 at 23:28
  • The USB port is mainly intended to put in a USB stick if you need to transfer some extra data (like drivers) to the server while you are installing it.
    – Tonny
    Jan 4, 2017 at 14:57
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    @Tonny I think the OP is talking about an internal USB slot, which is used exactly as the SD one: to install an embedded OS/hypervisor without touching the data disks.
    – shodanshok
    Jan 4, 2017 at 15:45
  • For a while, the internal USB port was sometimes intended to run a tape drive.
    – Criggie
    Dec 5, 2017 at 4:02
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    My Supermicro X-10 series motherboard has a USB B connector mounted on the board. I use it to hold the OS, a dedicated NAS appliance. @Criggie it's odd that your internal tape drive did not have a jumper-header connector instead.
    – JDługosz
    Dec 5, 2017 at 9:24
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You can use the SD card for example to outsource the /boot partition. e.g HP ProlianG8 G8 can not boot from HDD when the RAID controller is configured to HBA but you can still boot from the SD-Card.

Also you may by able (not tested) to outsource EFI fat partiotion to the SD-Card to by able to create a software RAID and load kernel / init from there.

FYI: Unfortunately the internal SD Card slot on Supermicro motherboards cannot be used for OS / boot partition and according to Supermicro is reserved for internal debugging use only

https://www.supermicro.com/support/faqs/faq.cfm?faq=29646

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Some years ago, the embedded PC motherboard used in a product had a CF card slot on the motherboard. The SD is probably a modern update to that.

For a device that will run embedded firmware, not a desktop or conventional server (e.g. a specialized medical imaging printer) this is a specific feature desired of the board.

As I recall, it was running Embedded XP, an older MS product for that purpose.

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