mike wrote:
> And terminology-wise, one or more zpools create zdevs right?
>
Lets get the terminology right first.
You can have more than one zPool.
Each zPool can have many filesystems which all share *ALL* the space in
the pool.
Each zPool can get it's space from one or more vDevs.
(Yes you can put more than one vDev in a single pool, and space from all
vDevs is available to all filesystems - No artificial bounadaries here.)
Each vDev can be one of several types.
Single - 1 device - No redundancy - 100% space usable.
Mirror - 2 devices min - Redundandacy increases as you add mirror devices.
Available space is equal to smallest device.
RAIDZ1 - 3 devices min - Redundancy allows 1 failure at a time.
Available space is (n-1) times smallest device.
RAIDZ2 - 4 devices min - Redundancy allows 2 failures at once.
Available space is (n-2) times smallest device.
You can ( though I don't know why you'd want to) put vDevs of different
types in the same pool.
>
> zpool create tank \
> raidz disk1 disk2 disk3 disk4 disk5 disk6 disk7 \
> raidz disk8 disk9 disk10 disk11 disk12 disk13 disk14 \
> spare disk15
>
> That's pretty much dual parity/dual failure for both pools assuming I swap
> out the dead drive pretty quickly. Yeah?
>
In this example, you have one pool, with 2 vDevs. Each vDev can sustain
one failure, but 2 failures in either vDev will take out the whole pool.
If you really can afford to trade performance (and no I don't know how
much you lose) for redundancy, it'd be better to do:
zpool create tank \
raidz2 disk1 disk2 disk3 disk4 disk5 disk6 disk7 \
disk8 disk9 disk10 disk11 disk12 disk13 disk14 \
spare disk15
Since now you can have any 2 disks fail (3 if the spare has time to get
used,) and the same space as your example.
-Kyle
_______________________________________________
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
