Gilberto Mautner wrote:
> Hello list,
>  
>  
> I'm thinking about this topology:
>  
> NFS Client <----NFS---> zFS Host <---iSCSI---> zFS Node 1, 2, 3 etc.
>  
> The idea here is to create a scalable NFS server by plugging in more 
> nodes as more space is needed, striping data across them.

I see people doing this, but, IMHO, it seems like a waste of
resources and will be generally slower than having the 
disks on the NFS server.

>  
> A question is: we know from the docs that zFS optimizes random write 
> speed by consolidating what would be many random writes into a single 
> sequential operation.
>  
> I imagine that for zFS be able to do that it has to have some 
> knowledge about the hard disk geography. Now, if this geography is 
> being abstracted by iSCSI, is that optimization still valid?

ZFS doesn't do any optimization for hard disk geometry.  Allocations are
made starting at the beginning and proceeding according to the slab size.
For diversity, redundant copies of metadata are spread further away, so
there may be some additional "jumps," but these aren't really based on
disk geometry.  In other words, I believe the optimization is probably still
valid.
 -- richard

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