On Mon, Jul 23, 2012 at 12:54:12PM +1000, Brett Pemberton wrote:
On Sun, Jul 22, 2012 at 4:14 PM, Craig Sanders <cas@taz.net.au> wrote:
On Sun, Jul 22, 2012 at 03:12:22PM +1000, Brett Pemberton wrote:
My current system has 2 x 64GB SSDs for OS, and a ZIL (mirrored) and is the ZIL mirrored, or just the OS partitions?
Right now, the entire block devices are mirrored. So yes, the ZIL is.
there's no benefit in having the ZIL mirrored, but it's probably not worth the hassle of changing it.
Bit disappointing, as I had chalked that down as a major advantage over mdadm.
the advantage here over mdadm (and/or lvm) is that you don't have to stuff around with manually resizing the fs. if autoexpand is on, as soon as a vdev has usable extra capacity, the pool uses it. "usable" depends on the exact details of the vdev(s).
I'm still confused as to why zpool list showed an increase in capacity after the replace operation.
iirc zpool knows about the extra capacity of the 1.5TB drive, but it's not available to be used by a filesystem.
Thinking about it further, I believe my best compromise might be to add one more drive into a 5.25 bay, and do:
3 x raidz, each with 3 drives.
[500,500,500], [500,500,500], [1500,500,500] ~ 3tb
sounds good.
And if I replace the two drives in the last vdev with the best bang for buck right now, 2tb,
bb4b depends on the diff in price between 1.5TB and 2TB drives (if you can still get 1.5TB drives - i'm not sure if they're still available new - maybe you can find some old but unused stock on ebay).
this will jump to 5.5tb (guessing)
unless/until you also replace the 1.5TB with a 2TB, you will only be able to use 1.5TB of each drive in that zdev. raidz-1 is like raid-5 so gives n-1 capacity for n disks. so, ignoring any potential gain from zfs compression or de-duping[1], 3 x 1.5TB drives = 3TB raidz. so that would be 1TB + 1TB + 3TB = total 5TB. upgrading that 1.5TB to 2TB as well would give you 1+1+4 = 6TB...an extra TB for the price of a 2TB drive (approx $130). probably not worth it. imo hold onto the money until 2TB drives are a lot cheaper or one of the drives dies and needs replacing or until it's time to upgrade one of the other zdevs to 2 or 3TB drives. [1] re: de-duping - not worth the bother, imo. with the amount of ram needed for it to be viable (estimates range from 1GB to 5GB RAM per TB of disk, just for the L2ARC), it's cheaper just to have more & bigger disks. zfs compression, OTOH, is definitely worth-while if most of the data you're storing is not already compressed.
Giving me a fully populated max of 12tb.
or more with 3 and 4TB drives.
Seems a nice mix of upgrade-ability, storage and redundancy to me.
yep. craig -- craig sanders <cas@taz.net.au> BOFH excuse #198: Post-it Note Sludge leaked into the monitor.