[OmniOS-discuss] zfs pool 100% busy, disks less than 10%

[Richard Elling]

[responding to myself, considering the audience]

On Nov 3, 2014, at 11:30 AM, Richard Elling <richard.elling at richardelling.com> wrote:

> 
> On Nov 2, 2014, at 6:24 PM, Rune Tipsmark <rt at steait.net> wrote:
> 
>> Looking a bit more at these numbers, am I seeing twice the actual rate due to mirroring?
> 
> You need to know what you are measuring. iostat and zpool iostat measure the I/O from
> the pool to the disk. This is often very different than an application to the file system (pool).
> In practice, it is often so different that it is impractical to correlate the two.
> 
>> How does compression affect the numbers?
>> 
>> Say I have 1 vdev mirrored and I see the pool writing 100 MB/sec, its what? 50 MB each disk? But from the client side only 50 MB/sec total? What if I compress it at the same time at say 1.50 ratio, will the pool show 100 MB/sec and the client write 75 MB/sec actual?
> 
> Measure both and compare. Usually we measure application side bandwidth using a tool
> such as fsstat.

actually, we measure it using some sort of data collector that stores data for long-term
analysis and includes handy graphing features (cue Circonus)
 -- richard