RAID Controller Failure

Question

This message was previously posted in the Hard Drive forum, however, a Dell representative recommended that I repost it here:

I planned to order several RAID 1 configured Dell Optiplex desktops for a client, but a person I work with told me about a problem they had with a Dell PowerEdge Server (not sure of the model number).

According to my friend, the RAID controller on the server went out and Dell had to ship out a new controller. The shocking part of the story was that when they got the replacement controller, the drives were completely unusable. Dell told him that this was normal procedure when controllers go out. Apparently my friend went round-and-round with Tech Support, but to no avail. He finally rebuilt the entire system from the ground up.

Still a little skeptical of the story, I contacted Dell Tech Support regarding the Optiplexes and an L2 tech confirmed that if the RAID goes out, the data on the disks is unrecoverable. I couldn’t believe what I was hearing!!! The whole point of RAID 1 is data redundancy – yet the controller still provides a single point of failure! If the controller goes bad, I would expect to replace the controller and bring the drives back online.

Does anyone know anything about this? I’m interested in feedback on both the PowerEdge Servers and the Optiplexes.

Dev Mgr · Answer

I'm not sure about chipset raid (Intel chipset that's used on Optiplex systems), but on the PowerEdge Raid Controllers (PERC) the disk config is stored on the drives and in the PERC bios (nvram). If you power down, replace the raid controller, connect the drives and power up, the PERC card (best is to be on the same firmware) should recognize the raid configuration and work with it just fine.

lsheets · Answer

Thanks for the feedback on the servers.  Does anyone else know about the Optiplexes or Dimmensions?  My sales rep didn't provide me with any other leads on who to talk to.  I've also contacted other Dell resellers I know who are trying to push this issue through their sales reps.  It has all of us pretty concerned about the reiability of systems we have installed.

mayukawa · Answer

From what I've seen the current line of PERC RAID adapters are just repackaged LSI Logic MegaRAID adapters, which have a very flexible architecture.  As DevMgr said, the configuration information is stored on both the drives and the RAID adapter.  Normally if the adapter failed, you can just pop in another adapter and the new adapter (which should have no configuration) will automatically copy the configuration from the drives.  If the adapter already has a configuration on it (and it's different then the one on the drives), it'll then ask you which configuration to use.  Which RAID adapter are you talking about anyway?  Are you talking about the chipset SATA RAID (which would require a motherboard change if it dies)?

lsheets · Answer

Yes. I was talking about the chipset RAID.

What I've found out is that chipset RAID (aka fake RAID) is really software RAID. It really can't be expected to perform as traditional hardware RAID.

My current understanding is that if the chipset-based RAID for a RAID 1 configuration fails and you cannot install the drives on in a new system with an identical chipset, there is little chance that you will be able to bring the operating system back up. Is that correct? In that situation, you're probably going to have to reinstall the operating system... In other words, a single point of failure (the chipset RAID) would result in the need to reinstall the OS. In fact, the OS would not even be restorable from backups because of the integration of the RAID drivers with the OS you'd be restoring.

Bottom Line: Chipset RAID is software RAID, not hardware RAID.

Locked Topics – Desktops General

RAID Controller Failure

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