How to configure a LSI MegaRAID controller to host non-RAID backup disks which allow hot swap

JustJoe

8/1/24, 9:22 AM

I'm running a server with a LSI MegaRAID controller that has 4 slots in the backplane for 4 SATA HDDs. Two of those slots are used for HDDs which are configured as RAID1 which is used as the "main storage" for the server.

Now I'm planning to make my backup procedure more robust. Currently I use 3 portable USB SSD drives where I connect one at a time to the server and let the backup software store the backup data on the SSD. I regularly flip the conntected SSD and store the other ones in a secure place. This setup works mostly well, except that the USB connection sometimes causes problems.

My idea is now to get two more caddies for the HDD slots of the server and to mount SATA SSD drives into those. In the end, I have 3 caddies which one SSD in each that are supposed to serve as backup media. In the same way as with the previous USB drives, I will the plug them round robin (one at a time) into the server (slot 0) and make the backup software store its data on the currently plugged in backup disk.

That is the theory. How should I configure the three SATA backup HDDs in the LSI/MegaRAID controller? One of the most important points is that I do not want to reconfigure/repare the setup every time I pull out and flip in a backup disk. My ideal setup would be that I can plug in any of those 3 disks into slot 0 of the backplane and the controller just mounts the drive in the same way as a USB disk would do, that I just plug into the bus.

Any ideas or recommendations would be great!

Thanks!

1 + 0

backup

storage

megaraid

megaraid-storage-manager

Score:1

Server

Zac67

8/1/24, 1:08 PM

You can run disks in a non-RAID configuration on a MegaRAID using the JBOD option.

However, since a RAID controller expects to always see specific disks and requires importing 'foreign' disks, a rotation scheme regularly causes drive errors (when removing) and careful insertion of (re)imported previous drives - both can seriously impact server monitoring and even resilience.

I'd seriously recommend not running that rotation scheme on the MegaRAID but on a separate, hot-plug capable SAS or SATA HBA. A simpler HBA doesn't (or shouldn't) have problems with rotating drives.

If you can't rededicate a drive cage to the new HBA I'd use an external case. If you use internal drive slots do mark them well to avoid accidental removal of production drives.

+ 4

JustJoe

8/1/24, 1:42 PM

Thanks for your feedback. The idea of using a separate "dumb" SATA controller for this purpose sounds feasible. Thanks!

JustJoe

8/1/24, 2:41 PM

My SuperMicro AS-1013S-MTR board has 4 SATA connectors which are all not used currently. Instead, the LSI MegaRAID controller card is connected with the 4 bays of the backplane. I checked the manual of the BPN-SAS3-815TQ backplane but I'm sure if I can just rip off one of the SATA cables coming from the MegaRAID controller and instead use a SATA cable to directly connect this bay to one of motherboards own SATA connectors, since besides the 4 SATA cables, there is also an extra cable called "sideband" which connects the backplane and the MegaRAID. Can this cause problems (mixed controllers)?

Zac67

8/1/24, 2:56 PM

Can't be 100% without more information, but when each bay is connected separately you can reconnect it to the SATA HBA - just make sure they're hot plug. The sideband connector likely won't hurt, but do make sure it doesn't signal fake drive swaps (swaps should be signaled in band).

JustJoe

8/1/24, 3:45 PM

Ok, thanks. I will give it a try... - and to let everyone know: It works. The MegaRAID seems to have no problem if one SATA port of the backplane is used by a different controller. The only thing is, that the LED indicators of the drive do not work any more (for the SSD on the different controller!); but that is, according the manual of the mainboard correct. So, I now have a setup where I can swap my backup SDDs easily on the fly without messing up with my RAID configuration. Thanks for your help!

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EN: How to configure a LSI MegaRAID controller to host non-RAID backup disks which allow hot swap

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