ZFS makes SSDs faster than memory!

[Ivan Voras]

On 07/23/10 15:20, Attila Nagy wrote:

> Maybe I should have written this first, but I'm not the only one reading
> from the machine.

You probably realize this makes all your performance data of suspicious
validity :)

> For random reads even the cheapest MLC outperforms a 7k2 SATA disk (only
> reads), and this is an Intel stuff, which can do 3000 RIOPS easily.
>> Are there any facts backup your assumption that data is really
>> read from memory, SSD, disk in the named cases?
>> E.g. by ARC/L2ARC and IO statistics.
>>    
> Yes. When downloading from L2ARC:
>  L(q)  ops/s    r/s   kBps   ms/r    w/s   kBps   ms/w   %busy Name
>     0    174    174  21505    0.8      0      0    0.0   13.3| ad4
>     0    169    169  21479    0.9      0      0    0.0   15.0| ad6
> when downloading from ARC:
>  L(q)  ops/s    r/s   kBps   ms/r    w/s   kBps   ms/w   %busy Name
>     0     26     19   1129    0.6      7     78    0.4    1.3| ad4
>     0     19     12   1436    1.1      7     78    0.3    1.4| ad6

So it looks like you encountered a problem where the memory-based ARC
cache read performance is incredibly bad?