> On May 2, 2010, at 8:47 AM, Steve Staples wrote: > > > Hi there! > > > > I am new to the list, and to OpenSolaris, as well as ZPS. > > > > I am creating a zpool/zfs to use on my NAS server, and basically I want some > > redundancy for my files/media. What I am looking to do, is get a bunch of > > 2TB drives, and mount them mirrored, and in a zpool so that I don't have to > > worry about running out of room. (I know, pretty typical I guess). > > > > My problem is, is that not all 2TB hard drives are the same size (even > > though they should be 2 trillion bytes, there is still sometimes a +/- (I've > > only noticed this 2x so far) ) and if I create them mirrored, and one fails, > > and then I replace the drive, and for some reason, it is 1byte smaller, it > > will not work. > > > > How would I go about fixing this "problem"? > > This problem is already fixed for you in ZFS. For disk sizes in 2TB it may > tolerate difference in size up to approximately a little bit less than half a > metaslab size which is currently likely to be 16GB, thus it may tolerate > difference in size of up to, say, 7.5GB. > > I think that in most cases difference in sizes is below that figure. > > You can see it for yourself: > > bash-4.0# mkfile -n 2000000000000 d0 > bash-4.0# zpool create pool `pwd`/d0 > bash-4.0# mkfile -n 1992869543936 d1 > bash-4.0# zpool attach pool `pwd`/d0 `pwd`/d1 > bash-4.0# zpool status pool > pool: pool > state: ONLINE > scrub: resilver completed after 0h0m with 0 errors on Sun May 2 15:25:24 > 2010 > config: > > NAME STATE READ WRITE CKSUM > pool ONLINE 0 0 0 > mirror-0 ONLINE 0 0 0 > /var/tmp/d0 ONLINE 0 0 0 > /var/tmp/d1 ONLINE 0 0 0 83.5K resilvered > > errors: No known data errors > bash-4.0# zpool detach pool `pwd`/d1 > > So you can see that even though difference in size between d0 and d1 is > 7130456064 (~6.6GB), it can still be attached just fine. Let's now detach d1 > and make it 1 byte smaller:
I've done this in testing already, and mirrored a 10gb drive, with an 80gb drive, and yes, the mirror assumes the 10gb size. But, if I remove the 10gb drive, and replace it with another 80gb, if the other 80gb drive is smaller by even 1 byte, you cannot attach it. > bash-4.0# mkfile -n 1992869543935 d1 > bash-4.0# zpool attach pool `pwd`/d0 `pwd`/d1 > cannot attach /var/tmp/d1 to /var/tmp/d0: device is too small > bash-4.0# > > This time is is no longer possible to attach it, because size is not enough to > fit the same number (116) of 16G metaslabs; And yes, I've gotten the exact same results when using file based "disks" (mkfile -n 1992869543935 d1) of 1byte less. Replacing with a bigger drive, is no problem, replacing with the same drive, that is 1byte smaller... cannot do. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
