# Adding 4K drives to a 512-byte pool



## spork (Aug 14, 2013)

I've got a RAID-Z1 pool made of three 1 TB Samsung drives (512 byte sectors) on my home server.  I'm running around 90% full now and needing to add more space.  I have a total of five internal SATA ports and one external eSATA.  My plan is to bring two 2 TB drives into the mix, likely as a mirrored pair.

Most of the 2 TB drives I'm finding that are somewhat affordable are 4K "advanced format" drives.

Are there any issues with having one set of vdevs (the existing RAID-Z1 group) and another set of vdevs (the new mirror group) with different physical sector sizes?

I currently don't back up the bulk of the pool because it's not terribly important.  I'm considering adding a 4 TB drive in an external case to back things up and give me some flexibility in shuffling disks around.  Obviously that's not a great backup (single cheap drive), but I was planning to use ZFS there as well so that I at least have checksumming.

If I go that route and I'm left with five ports, two 2 TB drives and three 1 TB drives, what might be a good option for making efficient use of all the drives?


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## cbunn (Aug 15, 2013)

spork said:
			
		

> Most of the 2 TB drives I'm finding that are somewhat affordable are 4K "advanced format" drives.



You might find that these 4K drives still report 512-byte sectors to the OS through emulation. This is to increase compatibility, but it mainly increases frustration. If that is the case, there are ways to get around it.



			
				spork said:
			
		

> Are there any issues with having one set of vdevs (the existing RAID-Z1 group) and another set of vdevs (the new mirror group) with different physical sector sizes?



Not to be pedantic, but you don't mean "set of vdevs", you mean vdev. The group of drives (RAID-Z or mirror) is a vdev. The pool is a set of vdevs.

But to your point, there shouldn't be any real problem with combining vdevs with different sector sizes into the same pool. Something to keep in mind, though, is that once added, you cannot remove a vdev without destroying the entire pool. So be sure you want to use the same pool for both your old RAID-Z and your new mirror.



			
				spork said:
			
		

> If I go that route and I'm left with five ports, two 2 TB drives and three 1 TB drives, what might be a good option for making efficient use of all the drives?



I suppose that depends on what you mean by efficient. Are you looking to combine them later on into a single RAID-Z? You can, but you'll lose half of the 2 TB drives in the process. Having separate vdevs (one mirror and one RAID-Z) is really the only way you'll be able to use the full capacity of each drive.

Have you considered a cheap SATA controller card? If you have an open PCI slot and some space in your case, it might be worth the effort. Or you might consider replacing the 1 TB drives with 2 TB ones later down the line to make a new pool with one RAID-Z vdev with all the 2 TB drives.


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## jem (Aug 15, 2013)

GPT partition the new drives, taking care to align the partitions to the 4K physical sectors.

Then add the partitions to your pool.


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