Understanding Vdevs and Vpool

[Bikerznet]

Hi

I have a question about adding vdevs to a vpool.

I currently have 5x 2TB disks in raidz set up as a vdev.

I already understand that you cannot add drives to an already created vdev and you grow the zpool by adding new vdevs, but want to know how the raidz arrays are handled across the zpool

as I add drives to my zpool, i.e setup new drives as a vdev (again raidz) I can then add these to my existing zpool, correct?

Now how does the zpool uses this vdev? does it stripe all my data across both vdevs, which in effect becomes raid 50! when you add a new vdev does the system move the data across the existing vdev and new vdev automatically?

As I am looking to use a 16 or 20 bay case I am looking to make my vdevs raidz using 4 disk in each and then add new vdevs as I need more space.

[raulfg3]

Now how does the zpool uses this vdev? does it stripe all my data across both vdevs

I think that is explain in easy way in this powerpoint: http://forums.freenas.org/showthread.ph ... ight=*.ppt

as I add drives to my zpool, i.e setup new drives as a vdev (again raidz) I can then add these to my existing zpool, correct?

YES, it's correct

[Bikerznet]

Thanks I have seen the powerpoint slideshow and understand the main points about devs and zpools, but this doesn't tell me what I have asked! Being if i have two vdevs in my zpool is the data stripe across these? and if this is the case does the system automatically move data across into the new dev?

So if I have a hardware raid setup, if I use Online Capacity Expansion (OCE) to add a new disk to my array , if I am using raid-50 and add a new raid 5-sub array it will automatically stripe the data across the new array.

I am just looking to see if ZFS does what I want, as it works the same way as building a hardware raid 50 system, if I lose a sub raid 5 array, i lose the whole array, much as if I lose anyone vdev I lose the whole vpool. The advantage of raid 50 give me the speed of the striped array while it also gives me the protection of a raid 5 array, while building a large raid 5 array has the problem of multiple points of failure in one area.

[raulfg3]

look at this article: http://constantin.glez.de/blog/2010/06/ ... erformance