As part of my home lab project which is still on-going (yes, I have been very quiet on this one of late), my plan has been to move my home server into a new chassis to match the other chassis I am using for the home lab. I use Storage Spaces on my home server but as I use an LSI MegaRAID card, I have all of my drives setup as individual RAID0 sets because the MegaRAID family of cards do not support JBOD.
My biggest worry with moving to the new chassis has been the storage and whether or not my RAID0 sets will come across and manage to keep all of my Storage Space data in tact as I have a lot of it and I’d obviously not like to lose it all. This worry is because of the changes in design. My current chassis uses a Reverse Breakout SATA cable to connect the drives, with an SFF-8087 SAS Multilane connection at the controller end and four conventional SATA connections at the drive enclosure end times four for the quad SAS channels on the controller card. The new chassis uses SFF-8087 to SFF-8087 SAS Multilane cables end-to-end and the backplane of the chassis handles the breakout to the individual drives. As a result, I can’t guarantee that all of the drives will be reconnected to the same channel and port on the controller during the move.
I got the chance this week to test this out as I had to add a new 3TB drive to the pool to add capacity. I added the drive to the server, configured a RAID0 for it but I set it up as a Simple NTFS partition disk and not a member of the Storage Space. I put some files on the disk and played around with different options moving the drive around. I pulled the new drive and re-inserted it in a different slot, now connected to a different channel and port but it came up with a foreign configuration on the drive, not exactly what I wanted.
I cleared the foreign configuration on the drive as importing these foreign configurations scares the hell out of me in the event that it overwrites the local configuration and blows away all of the drives including my RAID1 SSD pair for the operating system installation. After clearing the configuration, I created a new RAID0 set and added the drive to it however this time, I did not initialize the drive. After the virtual disk came online, instead of being uninitialized, it came up with the existing formatted partition and my existing test data, good but not perfect as I had to recreate the RAID0 set.
I was looking online for answers and nobody online seems to clearly answer the question how best to move disks around with an LSI MegaRAID controller, strange with these being some of the most dependable and popular cards on the market but I found my answer in the LSI documentation and a little under referenced feature called Drive Roaming.
Drive Roaming occurs when a disk is moved from one port or channel on the controller to another such as my case where I want to move to a new chassis and I am unsure whether all the drives will come back on the same ports and channels. Drive Roaming occurs at start-up when the controller starts up and reads the configuration in NVRAM on the controller and compares it to the configuration stored on each of the drives. This reading of the configuration allows a drive to be moved within the controller to another port or channel and remain configured as before but the emphasis here is on the at start-up.
When I first tested this, I moved the drive online so the drive did not roam, it was pulled and re-inserted. When I did a second test after reading the documentation, I moved the drive with the server shut down and indeed, the drive came back online with the same RAID0 set as configured before and all was working nicely. This is perfect because when I move between the chassis, I will be doing it with the server offline, shutdown and inert so I can now move all of my drives, safe in the knowledge that everything will be retained as was.
Because I know that nothing in IT goes as smoothly as planned however, my fallback option is to re-configure the RAID sets but select the No Initialization option for the drives. To this end, I have recorded the exact configuration of all of my RAID sets. I have recorded the RAID levels, Stripe Sizes, IO and Read Through settings. I have also recorded the current Port and Channel for each drive and the Model and Serial Number for each drive so that I can match the configuration back exactly as it is now. Consistency makes my life easier here. All my drives are 3TB, all Western Digital Caviar Red drives and all are in their own unique RAID0 set and all RAID0 sets are using the same Direct IO and Read Through setting so re-creating the sets is actually a cinch. The only exception is my operating system set which is configured as a RAID1 with two Intel 520 Series SSD drives and I’ve got the settings recorded for them too.
Last but not least, I’ve got my backups. My personal and important data is backed up to Microsoft Azure Backup using the integration with Windows Server 2012 R2 Essentials. To protect the operating system, I’ve got a Windows Backup created locally to a USB hard drive of the operating system partitions so that I can perform a bare metal recovery of the operating system if needed to the RAID1 SSD drives.
This post has been a bit of a waffle and a ramble but I hope that my learning of the LSI MegaRAID Drive Roaming feature helps somebody out there trying to investigate the same thing as me.