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Unplugging Drives on a RAID Controller Card... Caveats?

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June 7, 2012 2:35:20 PM

No matter how much I work with RAID cards and arrays... I always seem to make mistakes...

I'm wondering what the protocol is for unplugging drives from a RAID controller card (I'm using an LSI4x with a RAID 10 populated with 4 SSDs).

I want to unplug the drives and move them somewhere else... but the last time I did this a year ago I somehow broke the RAID array, and had to rebuild it.

1. If I unplug all the drives which are labeled as per the 4 to 1 connector (SATA/SAS) cable to the RAID card is labeled... and then reattach the drives in that exact order, on the SAME machine... I'm presuming there will be no problems upon restart? I DO believe that if you invert the order somehow though, the array will die (I believe this is what I did the first time by mistake)

2. However, I am also wondering, if I move this RAID card to another machine, and plug it in... will the BIOS recognize it, and boot the array... I'm thinking the Array data should be completely stored on the memory of the RAID controller... and thus it should be completely transportable?
June 7, 2012 2:57:41 PM

The array information should stay on the card. Reinstalling it exactly as you had it before sounds like a good option. The one thing that I'm concerned about is the status of the RAID card's battery. If it's dead, removing it from a powered, plugged in computer will mean losing the array configuration. While I don't have any experience with RAID cards, I do have a little experience using onboard RAID options.

In my experience, so long as everything is connected properly, the arrays show up regardless of the SATA connections I used. I even had to RMA my board once and with the new one (and I know it was new because it was a different revision, they had changed the SATA port layout) installed and my drives plugged into it, the arrays came back. Clearly, at least some information regarding the configuration is stored on the drives themselves.
June 7, 2012 3:21:58 PM

Raid configuration also stored on the drives as mentionned.. that is the only way you can replace a failed adapter without loosing the configuration :) 

Drive order is not important ... just need to be carefull when you boot up, the card should detect a mismatch configuration and prompt you ... that might of been your previous mistake when you lost your raid... Choose to load the configuration from drives and not the in memory configuration

Changing the adapter and drives to another machine should not be an issue since the configuration is server indepedent
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June 7, 2012 4:08:32 PM

Ah, ok, all this sounds quite logical. Presumably the information required to rebuild the array is stored on at least 2 of the drives (in a RAID 10 example) which is what allows the drives to rebuild themselves in the event of a disk failure.

I presume the MBR is also then written onto array member drives. I suppose this causes me to wonder what the RAM onboard the actual RAID controller is for then... presumably I/O operations for disk access.
June 7, 2012 4:08:38 PM

Ah, ok, all this sounds quite logical. Presumably the information required to rebuild the array is stored on at least 2 of the drives (in a RAID 10 example) which is what allows the drives to rebuild themselves in the event of a disk failure.

I presume the MBR is also then written onto array member drives. I suppose this causes me to wonder what the RAM onboard the actual RAID controller is for then... presumably I/O operations for disk access.
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