An order of magnitude higher IOPS needed with ZFS than UFS

[Attila Nagy]

On 06/12/13 13:40, Mark Felder wrote:
> On Tue, 11 Jun 2013 16:01:23 -0500, Attila Nagy <bra at fsn.hu> wrote:
>
>> BTW, the file systems are 77-78% full according to df (so ZFS holds 
>> more, because UFS is -m 8).
>
> ZFS write performance can begin to drop pretty badly when you get 
> around 80% full. I've not seen any benchmarks showing an improvement 
> with a very fast and large ZIL or tons of memory, but I'd expect that 
> would help significantly. Just note that you're right at the edge 
> where performance gets impacted.
I'm aware of that, even thought about it, that's why I wrote the disk 
free percents into my mail. I see a completely normal write pattern, but 
a lot of reads, so I guess ZIL wouldn't help here (maybe L2ARC or more 
memory, if something doesn't fit into it).

BTW, I think having the allowed fill value this low (UFS has the 
breakdown point much higher) is of a really bad design...