Replacing Full Height HDDs with ZuluSCSI - Printable Version

+- IRIX Network Forums (//forums.irixnet.org)
+-- Forum: SGI/MIPS (//forums.irixnet.org/forum-3.html)
+--- Forum: Hardware/Triage/Repair (//forums.irixnet.org/forum-11.html)
+--- Thread: Replacing Full Height HDDs with ZuluSCSI (/thread-4417.html)

---

Replacing Full Height HDDs with ZuluSCSI - CB_HK - 12-08-2024

Replacing Full Height SCSI Hard Disks with ZuluSCSI
 
Introduction

Back when I originally picked up my Crimson in 2017, I received a Full Height SCSI Hard Disk with it. Unfortunately, it didn’t survive the cross-country road trip and died shortly after I got back home. I tracked down a couple of Micropolis FH drives a while afterward, seeking to complete the Crimson as it would have been circa 1992. Sadly—and quite expectedly—these drives didn’t last long either. Their age coupled with their general intolerance of being handled in any way other than as delicately as possible made it unlikely to keep using an original FH drive. This was rather frustrating as I wanted the Crimson to not only be complete from an era-appropriate sense, but also be reliable.
During VCF SoCal 2024, I was introduced to ZuluSCSI. Rabbit Hole Computing, the creators, had a table setup along with a number of different variants of their board. I spent some time talking with them about the capability of ZuluSCSI and picked one up intending to experiment with it at some point. Half a year later and I’ve finally had the time to work on this project. I am happy to report that the ZuluSCSI is a fantastic replacement option for these older disk drives and coupled with a 3D printed enclosure to match the old FH drives along with a relay clicker to emulate the sound, I have found a fantastic and reliable substitute.

https://www.rabbitholecomputing.com/
 
Design

Two things were the most important when I was deciding how to integrate this board: 1) it had to operate seamlessly and not throw SCSI errors or create weird boot quirks. I just didn’t want to deal with something that didn’t work the same way as the drive it was intended to replace. 2) It had to look and sound like a FH drive from the time period.
Luckily, the first design consideration proved to be easy to deal with. Initial testing of the drive had already been done by others in this community and it had been shown that ZuluSCSI was capable of playing nicely with our machines. I pulled out my Personal IRIS (which I decided would be a perfect test case for the Crimson since I’d want one installed in the PI anyway if all of this worked out), and began to hook the drive up. The implementation is straightforward and doesn’t require a lot of work outside of setting a few parameters within the configuration file. The ZuluSCSI github page provides excellent documentation that made it very easy to get things going. Don’t forget to update your firmware! Also exceptionally easy to do: just drop the firmware file on the SD card and the next time you boot it will automatically install and continue running as intended with no reboot required.
Booting into sash and then fx, the ZuluSCSI was seen as a Quantum Fireball and fx immediately wrote the correct label to the disk. Repartitioning to a root drive was straightforward and then it was back out to attempt an install of 4.0.5. Of note, you set the overall space of the drive by creating a .img file within your modern OS (Windows, Mac, Linux)—instructions on the github page make this very easy to follow. I’m using 8 GB SanDisk industrial SD cards set to a 6.5 GB image on each.
IRIX 4.0.5 installed smoothly and with the speed expected of a standard SCSI drive (though it may have been a bit faster). The ZuluSCSI team has done a great job of iterating and improving on their design. They’ve released a good number of firmware updates and have managed to meet the specs for SCSI-2 transfer speeds. That being said, random reads will always be a bit slower than a traditional SCSI drive due to how SCSI-SD is implemented, but for this era of machine you’re not really going to notice that if at all. My anecdotal observation without running diskperf is that ZuluSCSI runs a bit faster than original hardware.

With the testing successful and IRIX running snappily, I moved onto designing a sled that would hold the ZuluSCSI and look the part of a FH hard disk. I also spent some time digging into any options that may exist for adding an appropriate clicking sound that would emulate the sound of the heads seeking. While ZuluSCSI has a spot on the board for adding a piezo speaker, the sound this makes is much more akin to newer drives, something like the later Quantum Fireball series. Since I wanted a more industrial clicking sound of a FH drive I turned to a device the Mac community had come up with: Beleth’s Drum. This small device is the creation of Infinity Products from Japan. It utilizes a small relay that makes a very audible clicking noise whenever the disk is accessed. There’s a bit more to it, including a microcontroller running some custom code that smooths out the response of the relay, making it much more appropriate sounding than just a binary on and off whenever the activity LED comes on. Armed with the two boards and a general idea of how I wanted the design to look, it was off to Fusion360.











3D Printing

With a solid design that balanced strength and less material, I started printing. One thing to note is that the front texture on most FH drives of the era can be emulated very well by the textured PEI beds that are on the market. In my case I used a Bambu Lab P1S with a textured bed to recreate the faceplate texture and it came out looking almost exactly the same. Once I had the three pieces printed I installed the heat-set inserts, the ZuluSCSI, Beleth’s Drum, and wiring. Installed in the sled it looked really slick.
 
I relied on heat-set inserts and screws from CNC Kitchen. A combination of M3 and M4 screws allows the faceplate, ZuluSCSI, and frame to be installed and removed as needed. You could glue the front plate to the sled if so desired, but I like being able to take things apart in the event something breaks and needs to be replaced. Of note, the frame and faceplate were printed in PLA, with the LED diffuser printed in clear PETG.



















Booting Personal IRIS with Completed Sled (YouTube)





Conclusion

The ZuluSCSI is a phenomenal replacement for these older machines. It is extremely simple to configure and does a great job of working just like the older SCSI drives it replaces. While there are no major quirks I’ve run across, I will note one minor issue: IRIX 4 and IRIX 5 are not able to accurately read the drive size within the disk manager application. The drive will show that it needs to be initialized and will report an incorrect size. That being said, inst reads the drive with no issue and shows total space, used space, and free space. I’m not sure why this discrepancy exists, but it’s something to be aware of and, at least in my experience, hasn’t been an issue with daily use.
 
Parts List

The .STLs are attached to this post so please feel free to download and use as you’d like! This is released to the community for free and I hope that if you decide to try out ZuluSCSI, or any other SCSI-SD solution, that this may be helpful for your project.

3D Printed
     -          ZuluSCSI sled (the main body that holds the device and, if desired, Beleth’s Drum) **print this with supports**
     -          Faceplate (attaches to the sled either with glue or screws) **print facedown on a textured PEI plate**
     -          LED Diffuser (holds 2x rectangular LEDs at 2 x 5mm in size) **printed in clear PETG**

Purchased (All linked to purchase pages)
     -          ZuluSCSI RP2040 (full size purchased from Rabbit Hole Computing)
     -          Beleth’s Drum (creates period-correct clicking sounds to emulate head seeking)
     -          Molex to 2x Berg Floppy (only needed if using Beleth’s Drum)
     -          Heat-set inserts and screws
     o   M3 x 5,7 (inserts)
     o   M3x6 (screws)
     o   M4 x 4,0 (inserts)
     o   M4x6 (screws)
     o   M4 x 8,1 (inserts)
     o   M4x10 (screws)
     -          Rectangular LEDs
 
 Thanks for reading!

---

RE: Replacing Full Height HDDs with ZuluSCSI - Raion - 12-08-2024

I haven't really messed with any of these kinds of devices since I got into SGI. As I recall people had issues with a similar device, SCSI2SD, is Zulu better? Also, doesn't the crimson use Differential scsi?

---

RE: Replacing Full Height HDDs with ZuluSCSI - CB_HK - 12-09-2024

ZuluSCSI seems to be really dialed in now. The folks at Rabbit Hole have taken feedback from the SGI community and have implemented firmware changes to make things run smoothly. My experience so far has been great with them.

As for the Crimson, it’s using standard SCSI-2. Nothing differential until the Onyx came along. So thankfully this is a good solution for it!

---

RE: Replacing Full Height HDDs with ZuluSCSI - Raion - 12-09-2024

How is the performance overall? Comparable when using a good card or better?

---

RE: Replacing Full Height HDDs with ZuluSCSI - Geoman - 12-09-2024

I'm more than impressed! This replacement has extremely high quality and high aestetic value! Thank you for sharing with the community!

---

RE: Replacing Full Height HDDs with ZuluSCSI - CB_HK - 12-09-2024

(12-09-2024, 02:35 AM)Raion Wrote:  How is the performance overall? Comparable when using a good card or better?

I’d say it’s at least comparable but I’m fairly certain it’s running faster than the stock drives. From what I’ve read all SCSI-SD devices have issues with random reads being slower but when reading from larger blocks of continuous data they are faster. The industrial SD cards I’m using seem to have no issue running consistently quickly even with plenty of use.

---

RE: Replacing Full Height HDDs with ZuluSCSI - jan-jaap - 12-09-2024

I like it. I like it so much I've printed one as a test (Bambu Labs X1E here). With ABS and without heating the chamber it warped a bit (ABS does that, and it was just a test), and I think it could use a bit of support in certain places too (we have support filament these days that can be easily removed).

But I'm extremely impressed with the design!

---

RE: Replacing Full Height HDDs with ZuluSCSI - Raion - 12-09-2024

Jan, why not use PETG? My experience has been when it comes to 3D printing (Keeping in mind my friend Rob Mink has made several printers that are now going viral) that it's a lot more forgiving and has a similar strength profile. The bad news is that you can't use acetone to try to hide the layers but for something like this I don't think that's a huge issue and bambu labs last I checked does support PETG filament.

---

RE: Replacing Full Height HDDs with ZuluSCSI - jan-jaap - 12-09-2024

We've only had this printer for a week or two. I'm still discovering. Used to have an Ultimaker 2, and that one had major issues with ABS so I was curious what this one would make of it.

---