12x zfs raid but starting with 8 drives.

[spacecabbie]

Hi and hello,

So i got a IBM ServeRAID M1015 and now am upgrading to sas i bought a bunch of HGST drives so want to go to 12 drives eventually.
As a hobbyist i lack funds to do it all in one go. So i want to hang 8 drives now and add 4 later is there anyway to do this on forehand ? Sinds expansion is not (yet) possible what would be the best just make it with 8 drives and wait for expansion to come along? Or can i set it to 12 vdev and only run with 10 for the time being ?

I am also open for any server chassis solution with 12x bay +sas expander backplane under 150 eur.

 

[sretalla]

You could run 2x RAIDZ2 VDEVs of 4 drives each and then add a 3rd VDEV of 4 when you want... later when expansion arrives, you could then make the VDEVs wider to add further/profit more from the capacity.

You could also do a VDEV of 6 disks now and add 6 more later... roughly the same capacity at the beginning, but more capacity at the end.

 

[sretalla]

set it to 12 vdev and only run with 10 for the time being ?

Not a good plan... this would run your pool in degraded state and be calculating everything from parity to work around the missing drives. Also, no protection if you lose one.

 

[spacecabbie]

You could run 2x RAIDZ2 VDEVs of 4 drives each and then add a 3rd VDEV of 4 when you want... later when expansion arrives, you could then make the VDEVs wider to add further/profit more from the capacity.

You could also do a VDEV of 6 disks now and add 6 more later... roughly the same capacity at the beginning, but more capacity at the end.

yea but i'd lose capacity especially since i run z3
thats 3 times the spare drives

 

[JaimieV]

Sorry, but there's no good workaround for this. Your options are to split to two vdevs; run RAIDZ3 degraded by two with 10 disks; wait until you can get more disks.

If you can't wait I would suggest two vdevs in RAIDZ2, six disks each. Create one now, extend to a second when you get the other four disks. As a bonus it'll be considerably quicker on writes than a 12-disk RAIDZ3.

For your other question: a chassis that capable is rare to find at that price, but disk shelves are quite easy. I'm using a Xyratex HB-1235, 12x3.5" disk SAS shelf over SFF-8088, see specs below. Cost me £75, plus £40 for the LSI HBA card and £15 for the cable.

 

[Scharbag]

As has been said, there is really no good way for you to do this. If you plan for 12 disks as a final solution, then I would recommend you use 2@6 disk vDevs. This has worked very well for me for years. It will end up using 4 drives for parity (once all 12 are in service) and will offer just slightly less space than the 12 disk RaidZ3 single vDev pool. It will be faster though.

Norco makes some cases that may suit, but they are not cheap. Plus you will need a SAS expander... Check my sig for how I deal with it.

Cheers,