Re: deciding UFS vs ZFS

--As of July 18, 2014 6:04:16 PM +0100, RW is alleged to have said:

>> "I was really more interested in whether ZFS (with ARC) is faster than
>> UFS with FreeBSD's own file caching. A lot of people say that putting
>> an OS on SSD gives a significant speed-up. 16GB should be more than
>> enough to keep the important system files in memory, so it sounds like
>> smarter caching might be useful."
>>
>> If you want speed sure UFS is faster on the same machine, but that's
>> because its doing less.
>
> Yes, I know ZFS has overheads, but ARC is potentially better than OS
> caching. The question was whether, with a decent amount memory, ZFS can
> actually be faster than UFS.

--As for the rest, it is mine.

Checking would take extensive work, and I think it would be *heavily* 
workload/hardware/tuning dependent, but I suspect there are probably cases 
where it would be.

For a similar type of example: Turning on compression in ZFS can improve 
speed, depending on the data and the hardware.  If it takes less time to 
compress/uncompress data than it does to write the difference to disk it 
speeds up; so with highly compressible data and light compression you often 
get higher speeds.

There are several of that types of trade-offs available in ZFS, and you can 
tune for different uses.  I don't think anyone has done comparisons, but 
it's probably possible that ZFS is faster under certain circumstances, even 
with a one-disk pool.

Daniel T. Staal

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