Recommended migration path to advanced format (4k) drives on existing SOHO FreeNAS server

[rico]

Hello,

I have a FreeNAS-8.3.1-BETA3-x64 (r13264) installation with (2) Seagate Barracuda 1.5 TB drives (model ST31500341AS) configured in a mirror (RAID1).

I’m running out of space and have purchased a single Seagate Desktop 3 TB drive (model ST3000DM001) to initiate replacing the original mirror. I intend to buy a second 3 TB drive as soon as I know the first ST3000DM001 will work in this server.

Since the original drives have 512 Byte sectors, and the new one(s) have the Seagate SmartAlign Advanced Format 4K sectors (4K physical emulated at 512-byte sectors), what is the easiest safe way to go about introducing the new drive(s)?

I am aware of 2 options:

(1) Replace one of the 1.5 TB drives with the new 3 TB drive and let the mirror rebuild. Once the mirror has rebuilt, replace the remaining 1.5 TB drive with a second 3 TB drive. Once the 1st 3 TB drive has copied to the 2nd 3 TB drive, the job is complete.

(2) Buy the second 3 TB drive now, then build a second file server with the (2) 3 TB disks. Initiate a copy across the network of all data from the old file server to the new file server. Once the old file server has copied to the new file server, the job is complete.​

Option (1) seems easier to me (requires buying less hardware and the copying is done automatically). Option (2) seems safer to me, but that could be just because this is my first foray into Advanced Format drives (and mixing them with non-Advanced format drives at that). I am worried that there are gotchas lurking there.

What do you recommend? And what should I look out for?

Thanks!

 

[dlavigne]

It may be a bit more complicated than that, depending upon the current block size and ashift value of the pool, as inserting a new drive into the existing mirror will keep the current ashift value of the pool. If it is not ashift=12, the new drive will be used inefficiently. An alternative is to add another mirror to the existing pool as the new vdev would get the new ashift, while the old vdev keeps the old ashift value. Or, to do a complete migration, create a new pool with new disks with ashift=12 and copy the data from the old pool.

 

[rico]

... Or, to do a complete migration, create a new pool with new disks with ashift=12 and copy the data from the old pool.

This sounds like the best option to me. Is this something I can do just by installing the 4k disk(s) into the existing server (adding them to the 512 sector-sized disks already there) and then clicking in the right places in the FreeNAS GUI?

Or is this option to be done strictly via the command line? I'm not opposed to the CLI. In fact I usually prefer it. I just have very little experience using commands such as zpool. And obviously I don't want to damage the existing mirror before the data has been copied to the new mirror.

 

[solarisguy]

Just be aware, that you would need to redo your pools, if you move to the current FreeNAS RELEASE version.

OK, you do not have to, but you might not be able to properly replace the disks, so you might as well redo your pool before it fails.

My recommendation would be to move to FreeNAS 9.2.1.9 using two 3TB disks. You can test your new drive with 9.2.1.9 without changing anything, just boot from a USB with 9.2.1.9 and remove the old disks from the system. Can your system run with 4 disks?

 

[rico]

Just be aware, that you would need to redo your pools, if you move to the current FreeNAS RELEASE version.

OK, you do not have to, but you might not be able to properly replace the disks, so you might as well redo your pool before it fails.

Are you saying that if I create the second mirror by adding the 4k drives to my existing FreeNAS-8.3.1-BETA3-x64 server (via running whatever commands are needed to keep the old pool intact for the 512 sector-sized drives while adding the second pool for the 4k sector-sized drives), then later upgrade to the newer FreeNAS, and then a disk in either of the mirrors fails, then I will have a more difficult (impossible?) time replacing the failed disk? Why would that be?

My recommendation would be to move to FreeNAS 9.2.1.9 using two 3TB disks. You can test your new drive with 9.2.1.9 without changing anything, just boot from a USB with 9.2.1.9 and remove the old disks from the system. Can your system run with 4 disks?

My system can run with 4 disks. I think you are suggesting that I go with a combination of dlavigne's third suggestion and option (2) from my original post. That is, build a new FreeNAS file server with the Advanced Format 4k disks. Then add the old 512 sector-sized disks to the server. That does seem like a simpler approach.

And actually I wouldn't have to build a new server. I could just take the 512 sector-sized disks out of the existing server, put the 4k disks in, then after the new mirror is created with the 4k disks, add the 512 sector-sized disks back in. Right? Or is there more to it to get the old mirror based on the 512 sector-sized disks to remain intact with its own pool separate from the pool for the new mirror based on the 4k disks?

 

[solarisguy]

I am glad that you found our suggestions suiting you.

However, I am not sure what steps you see, so let me outline my view of the process.

• save FreeNAS configuration on your desktop, and write down (paper or electronically) all the settings
• export the pool, shutdown, remove old USB and old disks
  
• insert new USB with 9.2.1.9 and new disks, power up
  
• configure FreeNAS (go by the manual with errata) and create a RAID-1 (mirror)
• test, verify, become comfortable with the new setup (permissions, management, access etc.)
  
• shutdown, insert old disks, power on
• import the old pool
• copy data from the old pool to the new one*
• after the copy is finished, export the old pool, shutdown, remove the old disks, power on
• enjoy

With the above process, your old disks and the old system are intact all the time.

* You can copy from CLI using zfs send and receive, or using your CIFS or NFS client or whatever you feel comfortable with.

 

[rico]

Thanks for the list and those details! I wouldn't have known to export the pool first. I'll have to go read up on that.