Build Raid Z for "future" disks?

[awinn17]

Right to it? Right to it. All I have read says you can only "expand" a Raid system if you retain the number of hard disks... but that you can replace a disk for a larger disk. Is that correct?

In other words, since I only need about 4-5 TB now, but want to be able to increase in the future, could I build an array with 3x2TB, 1x500GB, and 1x160GB?

That way later on I could disable and replace the 160 with a 2TB, resilver, and increase space. Is this just a theory and not possible in practice? To me the limiting factor seems to be that I haven't heard of Raid Z redistributing information when a larger disk is added, meaning any new data would be heavily applied to the new 2TB and not as well distributed/preserved?

Any thoughts on expanding capacity in the future without losing data?

Thanks!

[raulfg3]

. but that you can replace a disk for a larger disk. Is that correct?

YES

other words, since I only need about 4-5 TB now, but want to be able to increase in the future, could I build an array with 3x2TB, 1x500GB, and 1x160GB?

if you use raidZ1 for this configuration you only have 160GB x 3= 480GB, only if you replace 160GB disk in future By 2TB disk, your RaidZ1 expand to 500GBx3= 1,5 TB, and only when you replace 500GB in future by 2TB disk ( and all disk are 2TB disk) your pool expand to : 2TBx3= 6TB.

Remember that real free space is in GBy (1024^) not Gbi (10x10^3) so your real free space is 5,4 TB

PD: Because you use diferent size disk, when create raidZ1 pool, you MUST use -f (force) to create your pool.

[awinn17]

Raul you seem to run this place! Thanks for all your help so far.

I see. So the data would not have to be redistributed simply because it limits the space to the lowest common disk size, ie 160GB if I started with that as the lowest. Answers the question.

I'm just looking for a solution that lets me buy only as many disks as I need right now to save money, but not have to rebuild and face a data loss later when/if I need to expand the capacity.

[raulfg3]

I'm just looking for a solution that lets me buy only as many disks as I need right now to save money, but not have to rebuild and face a data loss later when/if I need to expand the capacity.

chapest is to use ZFS mirror, so you only need 2 disk to increase capacity, you start with 2x2TB so you have 2TB free, when need more space add 2 disk in mirror to existing pool so you have (2TBx2TB)+(2TBx2TB)=4TB free, if later you add other 2 , 4TB disk ( see that in a few years 4TB disk are cheap), you have (2TBx2TB)+(2TBx2TB)+(4TBx4TB)=8TB free


and please read this excelent powerpoint: http://forums.freenas.org/threads/slide ... oobs.7775/

[awinn17]

chapest is to use ZFS mirror, so you only need 2 disk to increase capacity

and please read this excelent powerpoint: http://forums.freenas.org/threads/slide ... oobs.7775/

Yes I have considered that as well. Isn't that kind of Raid 1-0? Mirrored-Stripe?

Will check out power point asap!