# ZFS Two Pools vs RAID0



## jigzat (Apr 4, 2013)

Hello everyone, I have a FreeBSD machine that works as a multimedia server. It consist of three HDDs. One 500GB for the system and Two 2TB for storage. Now, I know ZFS is meant for protect your data, but I cannot Physically add more HDDs since I would need a new PC with more SATA ports and space. I just added one HDD and created a pool with a simple [cmd=]zpool create FARLEY ada1[/cmd] I moved all the data to that HDD and now I installed the second HDD and the system immediately added that second HDD to the FARLEY pool. I tried to create second pool for the second one and I couldn't since 
	
	



```
/dev/ada2 is part of active pool 'FARLEY
```
 I tried to detach by [cmd=]zpool detach FARLEY ada2[/cmd] but 
	
	



```
cannot detach ada2: only applicable to mirror and replacing vdevs
```
.

I don't want to create a RAID0 because in case of failure I guess it would be easier to import one single HDD than a RAIDED0 pair. 

How can I detach the second HDD so I can create a second pool? and are there some opinions agains't doing it in that way?


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## kpa (Apr 4, 2013)

Post the output of `# zpool status`. I suspect that the disk ada1 has changed to ada2 for some reason and the pool is now a single disk pool consisting of just ada2


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## jigzat (Apr 4, 2013)

Thank you very much for the fast answer, this is the output:


```
pool: FARLEY
 state: ONLINE
  scan: none requested
config:

	NAME        STATE     READ WRITE CKSUM
	FARLEY      ONLINE       0     0     0
	  ada2      ONLINE       0     0     0
```

also/dev/ ls this:


```
ada0
ada0p1
ada0p2
ada0p3
ada0p4
ada1p1
ada1p2
ada2
```


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## kpa (Apr 4, 2013)

Yes, when you added the new disk the device names got shuffled around and the ZFS pool is now on ada2. You have to now figure out which one of ada0 and ada1 is now the new disk that you want to use for the second pool.


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## jigzat (Apr 4, 2013)

That is weird, I would have thought that ZFS would follow the system's device order because the output of /dev/ is correct. ada0 is indeed the boot disk and it has 4 partitions and ada1 correctly shows the two partitions created during the first zpool creation. This is like a Russian roulette, is there any safe way to check which one is?


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## kpa (Apr 4, 2013)

The problem is that the kernel, not ZFS, will change the device order if you plug in the disks in such away that the new disk is on a lower numbered port than the old disks.


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## jigzat (Apr 4, 2013)

Thank you very very much, I just opened the PC and unplugged the second 2TB HDD and this is the output of /dev/:


```
ada0
ada0p1
ada0p2
ada0p3
ada0p4
ada1
```

It was my mistake the other two partitions were in the second 2TB HDD already. But I have a doubt, how come the ZFS disk doesn't show any partitions under /dev/?


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## kpa (Apr 4, 2013)

If you use the full disk there are no partitions to show.


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## jigzat (Apr 5, 2013)

Thank you for your help an patience.


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