zpool attach makes a non-mirror into a mirror. zpool detach makes a mirror 
into a non-mirror.

I believe you are looking for zpool remove.

On Wednesday, October 29, 2014 12:54:48 AM UTC-7, Busty wrote:
>
> Wow, thanks Bjoern for that, now I really know what was going on. I 
> really appreciate the time you took to explain all that. 
>
> The problem I'm facing is, that I can't detach the drive. A "zpool 
> detach pool diskx" gives me the error: 
> "cannot detach diskx: only applicable to mirror and replacing vdevs." 
>
> I managed to format the disk as hfs+, zero the drive completely and 
> then format as zfs, but zfs still considers this disk as one of the pool. 
>
> What can I do to get the drive out of the pool? 
>
> On 26.10.14 14:43, Bjoern Kahl wrote: 
> > 
> > (this is going to be a bit longer, but since it is a reappearing 
> > topic I'd like to provide some background information on what 
> > happens behind the scene) 
> > 
> > 
> > Am 26.10.14 um 12:09 schrieb 'Busty' via zfs-macos: 
> >> This generated a follow up question: 
> > 
> >> I did the zpool replace with an unformatted disk as described in 
> >> the oracle documentation. After that, zpool status showed the 
> >> disk as part of the pool, but as "disk2", not as "disk2s2". 
> >> Accordingly, OSX wanted to initialize the disk every time upon 
> >> booting. 
> > 
> >> So I formatted the disk as described in the getting started 
> >> guide on MacZFS, which resolves the problem of OSX wanting to 
> >> initialize the disk, but still it shows as "disk2" (without the 
> >> s2) with zpool status. I was prepared to resilver the disk again 
> >> after that, but it was still part of the pool. 
> > 
> >> I started a scrub, had 6 checksum errors on that disk right at 
> >> the beginning, but otherwise the scrub seems to consider the data 
> >> as good. It is at 7 percent right now. 
> > 
> >> Should I be worried that the data is not integer? 
> > 
> > Yes, you should. 
> > 
> > You basically did the following: 
> > 
> > 1) 
> > 
> > Gave a whole disk to ZFS, telling it, it is OK to use the whole 
> > space from first to last block of the disk. 
> > 
> > ZFS did so and started writing data: 
> > 
> > a) it's vdev label 0,1 from block 0 to 1023 (assuming 512 byte 
> > blocks) 
> > 
> > b) it's vdev label 2,3 from block N-1024 to N-1 (assuming N block 
> > on disk) 
> > 
> > c) your pool data in between, following it's somewhat complex 
> > allocation scheme 
> > 
> > 
> > 2) 
> > 
> > Told OS X to write a disk label (aka GPT) on the disk. 
> > 
> > OS X did so and started writing data: 
> > 
> > a) A protective MBR in block 0 -> no damage, ZFS anticipates that, 
> > leaving block 0 to 32 (16k) of its label alone. 
> > 
> > b) The primary GPT structures, starting from block 1 (byte 
> > position 512) to end of block 33 (byte position 17408). This 
> > trashed part of the configuration dictionary in vdev label 0 
> > 
> > c) The secondary GPT structures, in the last 17408 bytes of the 
> > disk, overwriting part of the uberblock array in vdev label 3. 
> > 
> > d) The Mac OS X EFI area, usually around block 40 to 409600 (byte 
> > positions up to 200 MB). This is "/dev/diskXs1". 
> > 
> > e) The man partition "/dev/diskXs2", roughly starting at block 
> > 409640 and extending until some blocks before the secondary GPT 
> > structures. This is just created but nor written in "noformat" has 
> > been used. 
> > 
> > 
> > 
> > What does this mean? -------------------- 
> > 
> > 
> > It depends on how ZFS sees the disk.  Most likely it will continue 
> > to use "diskX" (no slice).  In that case: 
> > 
> > The pool keeps functioning, since vdev labels 1 and 2 are undamaged 
> > (0 and 3 are overwritten, see above) 
> > 
> > ZFS will almost instantly fix it's labels, completely overwriting 
> > the secondary GPT.  Mac OS X doesn't care, it writes the secondary 
> > GPT and never looks there again. 
> > 
> > The situation on the is start is more complex. 
> > 
> > ZFS will also almost instantly fix its label 0. However, this 
> > writes only from block 32 on (byte position 16384 onwards), since 
> > it completely ignores the first 16 blocks (supposed to hold disk 
> > identifier) and doesn't touch the next 16 in normal operation, 
> > since they are supposed to hold ZFS boot code and are unused in 
> > current implementations. 
> > 
> > So the rewritten vdev label 0 trashes the last 512 bytes of the 
> > primary GPT.  This does concern Mac OS X and you should see a 
> > waring about an invalid GPT CRC in the system log after boot. 
> > 
> > 
> > So much for the administrative data structures.  What about your 
> > data? 
> > 
> > ZFS' data area starts after the vdev label 1, i.e. at block 1024 
> > (byte position 512 kB).  This is somewhere inside the EFI area, 
> > overwriting whatever Mac OS X placed there (depends on version, 
> > older Mac OS X version didn't placed anything there, don't know for 
> > newer versions).  In any case, Mac OS X does not access the EFI 
> > area in normal operation, and so won't note the damage. 
> > 
> > On the other hand, Mac OS X is initializing the EFI area when 
> > initializing a disk, placing an empty FAT file system there. 
> > 
> > This FAT overwrites part of the ZFS pool data and caused the 
> > checksum errors. 
> > 
> > 
> > What to do now? --------------- 
> > 
> > I would detach the disk in question, zap the first and last several 
> > MB of disk space (i.e. of diskX itself, not of the diskX2s slice) 
> > by writing zero bytes to disk, for example using "dd", reformat 
> > with diskutil and reattach as /dev/diskX2s. 
> > 
> > Another approach for zapping the disk content is, to format as 
> > HFS+ with diskutil and then select "clear/erase free disk space" 
> > (or whatever the English button label says). 
> > 
> > 
> > Best regards 
> > 
> > Björn 
> > 
> >> On 23.10.14 14:01, 'Busty' via zfs-macos wrote: 
> > 
> >>> This was in fact easier than I thought. What did the trick was 
> >>> to physically swap the faulty disk with a new one and then 
> >>> "zpool detach (faulty disk)" 
> >>> 
> >>> After that a "zpool replace" went like a charm. 
> >>> 
> >>> Problem solved. 
> >>> 
> >>> On 15.10.14 20:32, 'Busty' via zfs-macos wrote: 
> >>>> In my pool, I had a disk that got a smart error (bad block), 
> >>>> so I pulled it out, installed a new one and made a "zpool 
> >>>> replace disk5s2 806745480046791602". (That number was shown 
> >>>> when typing "zpool status" as the missing device.) 
> >>>> 
> >>>> The resilver process started, but it seems that the new disk 
> >>>> is faulty, because it disappears from the device list 
> >>>> infrequently, but still at least every 6 hours (I have 
> >>>> Temperature Monitor running which shows me all disks by 
> >>>> serial number). 
> >>>> 
> >>>> So I want to change it. But zpool detach <poolname> 
> >>>> dev/disk5s2 gives the error "no such device in pool". 
> >>>> 
> >>>> How can I abort the resilvering process? Or is there another 
> >>>> way to restart the resilvering with a new disk? 
> >>>> 
> >>>> The original disk with the bad block is already on its way 
> >>>> to Western Digital (it was still in warranty). 
> > 
> > 
> > 
>

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