I have lots of experience with this.
Plug the drive into your SE/30. Boot from a disk that has System software. Use FWB Hard Disk Toolkit version 2.5 or 3.0.
Partition the drive as follows:
10MB Macintosh partition -set it to not auto mount. This is the partition that will hold your SCSI driver.
1.9GB (1900MB) Maximum second partition. Use it for your system folder.
1.9 GB third partition. This will show up as your second partition once booted.
Final partition for remaining size.
The SCSI manager on 68K Macs cannot handle drive sizes over 4GB without doing this, and cannot boot if the disk driver and system software are not contained in the first 2GB of the drive.
Here’s the text of a post I made about this on Reddit:
Pro Tip: Using large SCSI hard drives in old Macintosh machines (including Ultra 160 and Ultra 320)
I purchased a PowerMac 8600 that included a 4GB hard drive. The drive died. When I removed it I discovered a special adapter board and the drive was not 50 pin SCSI. The drive was actually a U160 drive with a SCA 80 to SCSI 50 pin adapter.
In the aftermath I discovered this whole new realm of SCSI. And the inexpensive large drives that are in it.
I found a lot of 4 Quantum Ultra 160 drives 18GB on eBay for $25 US including shipping. That’s about $7 a drive.
I tried to format one. I ended up killing it. Now down to 3.
Classic Mac OS is old. Dealing with drives this big requires special considerations. To save yourself some time, here’s a brief rundown of my experience on a 68040 Mac running System 7.6.1.
FWB Hard Disk Toolkit 3.0 is your friend here. The driver for the drive along with the first partition must exist in the first 1GB of the drive.
Easy solution: Use Autoformat to format the drive as a single volume. Then unmount. Set drive to not AutoMount and resize it to 10240 bytes (10MB). Create a 1.9GB or smaller partition for your OS. Then create another partition of the remaining drive space.
Boom! You can now boot older System 7 versions on a real SCSI drive on an 68k Mac with tons of GB of free drive space, using inexpensive decommissioned server drives.
YMMV regarding drive compatibility. I’m currently buying several brands and models and sizes to try on various old Macs and I plan on building a nice vintage Mac SCSI drive compatibility table for everyone to reference.
Yes I know about SCSI2SD. I’m more of a purist. Plus, I think this is more compatible and it’s far, far cheaper. 34GB drives are under $25 USD and the adapter boards are about $13.