SGI: Hardware

So I tried to reinstall IRIX onto Gaira as the internal 3.5" wasn't booting. Well I learned the drive had failed as I can't get to it in the command monitor.

So I take the front of the Indigo2 off, yank the HDD and lo and behold its a 50-pin connecting to a 80 pin adapter. Awesome, I thought as I pulled the old drive and converter out. One issue: the drive won't fit in either sled style I have and connect to the SCSI at the back. I could use one of my 50 pin adapters lying around but I'd rather just hook the drive in directly and minimize the hardware going into it. Seems unnecessary to use two adapters.

Anyone have any idea on how to directly hook it in? Do I need to make a cable or something or does someone have one pre made or something. I have a NOS UW 72GB 10k RPM SCSI drive waiting to go into Gaira.

I've used 2.5" Seagate Savvio SCSI drives w/ 80 pin SCA connectors, added an 80<=>50 pin adaptor and a 2.5" - 3.5" mounting bracket, and fitted the entire assembly to an Indigo2 drive tray. I've got the pictures around here somewhere, waiting for a write-up...

I'm sure I've mentioned this in other threads, some of the inspiration came from a thread by Geoman about doing this for the Octane ( viewtopic.php?f=3&t=16724686 ), but I don't seem to have any of the other threads bookmarked.

smj wrote: I've used 2.5" Seagate Savvio SCSI drives w/ 80 pin SCA connectors, added an 80<=>50 pin adaptor and a 2.5" - 3.5" mounting bracket, and fitted the entire assembly to an Indigo2 drive tray.

I bet if you worked at it, you could get one of those '4 ea 2.5" drives on one 3.5" tray' thingies stuffed in there. RAID-inna-sled, that'd be spiffy in an indigo or octane

Umm SMJ it looks to me like there's already an UW SCSI connector at the back: why do we need the second converter. I'd like to skip that step and get a direct UW connection because KISS

AFAIK, the connector at the back is not a standard SCA connector. It's simply a proprietary connector that SGI used on the Indigo2 to allow them to use their own quick-release drive sleds.

Both the hard drives in my Indigo2 are SCA ones and it's a simple matter of connecting the ribbon and power cables up to the 50->80 adapter, then connecting up the HDD. It's a bit of a snug fit for a 3.5" drive, but they do fit fine. Only thing to be careful of is that the power pins of the connector do not make contact with the metal chassis of the hard drive. I have a piece of cardboard wedged between the adapter and hard drives in my system to protect against this. Initially I had some gaffer tape and that wasn't enough. Still, at least I found out that the PSU of the Indigo2 is resilient enough to withstand a short being placed across it whilst in use

Okay. Guess I'll order some adapters... Thanks fellas

I had been under the impression that it was just a proprietary connector, but the Hardware Developer Handbook 2.0 says:
"The 80 pin connector and pinout used for both of these sleds is identical to the new SCA
type connector and pinout used on the O2, OCTANE, Origin200/2000 and Onyx2 systems."

However, it adds that "The location of the connector on the back of these sleds does not allow an SCA drive to be
plugged directly into the connector of the Indigo2." which could mean the spacing around the connector doesn't allow for it. But it should be possible to connect an SCA drive using a ribbon cable with SFF8151 connectors at either end, without any adapters. You just need to keep the stub length as short as the cables SGI uses in its sleds.

Does anyone want to make me a cable then? I'll compensate for time and shipping if they do so. I'd do it myself, but my soldering skills are atrocious and I don't want to risk shorting my I2 out.

I hadn't thought the connectors were compatible with proper SCA - I thought they were inverted or something at minimum - but live and learn. Even so loose drives rattling around will work, but it's nice to use the sleds. You're going to be stuck with 10MBps SCSI either way. But if you secure the drive to the sled, in 2 months to 2 years from now when you move the machine you won't have to hear the sickening "thunk" to remember "Oh right, the drive is loose in there!"

Yeah I'm not tota;;y worried about 10Mbit SCSI, this is a storage server so I don't need speed.

Thing is, having had a good look around, the first challenge would be to buy the connectors in the first place (they don't seem to be easy to acquire by themselves). Then you have the issue that most SCSI connectors for ribbon cables are designed to be easily clamped onto the cables, but SCA was never designed to be connected to a cable, hence there's a lot of very fiddly soldering that would be required.

The third issue is the lack of mounting clips or anything to hold the connector in place. SCA is designed to be much lower in friction than 50/68 pin connectors (which use the friction between plug/socket to keep the cable attached), and is designed to use the physical case mounting of the hard drive's bracket to hold the contacts of the connector in place.

Result would be the difficulty of acquiring the connectors, lots of fiddling to solder the thing properly, the fact that the HDD itself would be loose, and that it would not take much to get the connectors/cable to work loose (over time, vibrations from the HDD/fans might be enough).

I can't help but think from a "KISS" point of view that just attaching a 50pin>SCA adaptor to the HDD then bolting it to the proper Indigo2 cradle is actually likely to be a quicker, simpler and far more robust solution and that you'd only go down the custom-cable route if you really wanted a challenge. I'd be interested to see it done of course, but just saying...

I found some old notes I made about using SCA connectors with ribbon cables, and there is an AMP/TE Connectivity part number: 1734098-8. This is not labelled as SCA but it looks very similar and might be compatible. It mounts to a ribbon cable.

For now I yanked the adapter from my A3000 and put it in there. I have a few drive caddies I'm willing to volunteer if someone wants to give it a shot.

smj wrote: I hadn't thought the connectors were compatible with proper SCA - I thought they were inverted or something at minimum - but live and learn. Even so loose drives rattling around will work, but it's nice to use the sleds. You're going to be stuck with 10MBps SCSI either way. But if you secure the drive to the sled, in 2 months to 2 years from now when you move the machine you won't have to hear the sickening "thunk" to remember "Oh right, the drive is loose in there!"

One could still cut off the back plate of the original drive sled and make a pair of U shaped brackets to attach the drive further up and to the back (and optionally provide mounting holes for the front cover). Maybe that drive sled without the electrical bits I have in a drawer somewhere will be useful again some day if I get my hands on an Indigo 2.