I often see that the argument for using hardware raid is to be able to initiate an automatic rebuild by just swapping a faulty drive for a new one.
A lot of people assume that software raid can't do that. But that's incorrect.
Software raid on linux (as in md managed by mdadm) can do the exact the same thing.
It's under policy and partition policy in mdadm.conf. You'll find on the man mdadm.conf page.
The spare-same-slot option would be the one that works the same way as hardware controllers usually do.
I haven't used it myself since I prefer to initiate the rebuild myself. But I wonder if you guys have used it?
I don't think blind swap is about automatic rebuild, that's a given no matter what software/hardware RAID is running. It's more about seeing the light is red instead of green on drive 6, so you know that is the one to replace.
The only example of not having that available, that I can think of, is https://www.45drives.com/
I don't know man.
A typical SMB would have no monitoring and any server would be stuck in a closet somewhere. Nobody would notice any red lights until several months later or until something breaks and then they'd have no clue what to do about it, wouldn't know who to call and wouldn't have any idea if the server even has warranty (it never has). A spare drive wouldn't be available unless it was an old discarded drive left on the shelf from the last time something was replaced.
While probably true, that doesn't really have anything to do with blind swap.
I'm just saying those that have their server park under control doesn't really need any LEDs. And those that really needs it, doesn't look at it.
But it would actually be a small thing to make a script that would indicate faulty drives. You look at /proc/mdstat and any drive showing a _ instead of U is lit up on the drive bay. It's controlled by SGPIO or SES. That's how the raid controller does it.
I thought MD was already capable of performing this. . .
I don't think so but I could be wrong.
I mean you could run raid 1 on a pair of sd cards. Since that md works on any type of block device or partition there is no guarantee that there are any drive bay lights or anything of that nature. But it's possible that there is an option for it.
Has a quick look and it looks like the ledmon package monitors md arrays and set LEDs accordingly.
So yes, software raid can indicate what drive has an error directly on the chassis with some additional software.