Does hot-swap require special backplane?

H

Hurin

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Oct 8, 2003
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Hi all,

To make a long story short, I've got a custom-built server running an Adaptec 5805 SATA RAID controller with directly attached WD RE4 drives. There is no backplane.

I was able to disconnect a failed/missing drive that wasn't showing up in Adaptec Storage Manager (Windows running), and then I rescanned on the controller and confirmed that everything was alright.

When I reconnected the drive (power first, then data), first Storage Manager declared the logical volume to be "failed". . . then the server itself rebooted suddenly (may have been a BSOD, I wasn't able to see the console from where I was).

Upon rebooting, everything was alright. The (RAID 1) array began to rebuild. But. . . since I have a vague recollection of hot-swapping causing trouble years ago on the same server when I was testing it prior to deployment. . . I have to ask. . .

Should this work without a backplane? Should I be able to plug and unplug drives that are directly attached on a RAID controller that supports hot swapping?

--H
 
A backplane is simply what the drives plug into, so if you're actually using the drives, you either DO have a backplane, or if you're just hooking up regular SATA cables then that's fine (just less convenient as far as hotswapping goes). A bad backplane could possibly cause issues like that.
 
You should be able to do it without a backplane as long as the controller supports it, but I would not recommend it.
 
TheDingy said:
You should be able to do it without a backplane as long as the controller supports it, but I would not recommend it.
Click to expand...

What are you talking about? If there is no backplane, you just hook up cables directly, and there is NO downside to doing such a thing except that it takes more work to swap drives. If there is a PCB at the back of your hotswap enclosure, that IS a backplane. You either have a backplane or you use standard cables as if you weren't using a hotswap enclosure.
 
I think he means is hot swapping really only wise with a backplane? Or is the backplane nothing more than a more convenient way of plugging/unplugging a HDD and is otherwise no different than SATA and Molex cables?

I would assume the latter. Hot swapping is hot swapping, whether you do it with a backplane or cables, it matters not. But that's my ignorant take on it.
 
SATA and the SATA power connector were designed with hot-swappability in mind, which is why there are a million ground traces in the connectors and the ground traces are longer than the data/power traces ensuring ground always contacts first. This makes the chances of issues during hot-swapping lesser. You may absolutely hot swap them. Only downside is that it takes more effort. Well that and there's a chance that you might bump an unrelated wire and disconnect it by mistake. Edit to add: I'm not saying I recommend doing that. Just that it's fine... if you don't bump any other cables off.
 
CMadki4 hit the nail on the head the problem is that I would never open the case to a powered up machine and do maint on it esp if it is in production.
 
Just wondering why this RAID controller that allegedly supports hot swapping crashes the server when a failed drive is disconnected and then reconnected (and then spins up).

Heh, I'm not sure how I could have been clearer, but I'll try: The cables are going directly from the RAID controller to the hard drives. Direct, SATA fan-out cables from the RAID controller, directly into the drives.

I wouldn't have thought a backplane would be necessary. But my only other theory is that the RAID controller and/or its drivers are faulty and are not properly allowing for hot swapping.

As for it being foolish to take the cover off a server and disconnect a failed hard drive while it's on? Well, I guess I'm a fool then. But all signs seemed to indicate that it should not have caused a problem. And unless I'm stupid enough to have liquids and/or other potentially dangerous stuff around the server, I see no reason to shut it down for what should be a routine plug/unplug operation (again, if the RAID controller was behaving as advertised).

Thanks for all the input though guys. I guess I'll just chalk this up to the RAID controller being picky and I'll do all drive swapping when it's off.

--H
 
I just hot-swapped some drives on my LSI 9240 (IBM M1015) controller last night using just standard cables. No issues. For what it's worth, I think Adaptec controllers aren't too good. I hated the 3085 I had. A lot. I only recommend LSI (or LSI-based at least) controllers, personally.

Do make sure you have the latest firmware and drivers.
 
dandragonrage said:
SATA and the SATA power connector were designed with hot-swappability in mind, which is why there are a million ground traces in the connectors and the ground traces are longer than the data/power traces ensuring ground always contacts first. This makes the chances of issues during hot-swapping lesser. You may absolutely hot swap them. Only downside is that it takes more effort. Well that and there's a chance that you might bump an unrelated wire and disconnect it by mistake. Edit to add: I'm not saying I recommend doing that. Just that it's fine... if you don't bump any other cables off.
Click to expand...

NOT ALL are designed the same. Plenty that are same length pins and will end up in likely damage. Plugs/sockets need to be Hot-swappable as do the backplanes (power controlling type) and the HBA or RAID card.
 
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