On Nov 14, 2014, at 5:44 PM, Andrew Kinney <[email protected]> wrote:
> Richard Elling via illumos-discuss wrote:
>>> Is there a known reason why I'm seeing double writes to the slog? Am I
>>> alone or are others also seeing the same data amplification for sync writes
>>> with a slog?
>>
>> You are seeing allocations, not the same thing as writes. zpool iostat is
>> not the best tool
>> for understanding performance, for this and other reasons. What do you
>> measure at the
>> device itself?
>
>
> Fair enough. What would be the best way to measure the quantity of data
> actually written to the device?
Most commonly used is:
iostat -x
or
iostat -xn
>
> Obviously, I know what dd did and I can see what landed on the pool. I'm just
> unsure how to measure how much was written to the slog if it's not
> represented by the "allocation".
zilstat will show you the difference between blocks allocated and bytes
written, but it doesn't
show what is put on a specific disk because it measures ZIL activity, not disk
activity.
-- richard
-------------------------------------------
illumos-discuss
Archives: https://www.listbox.com/member/archive/182180/=now
RSS Feed: https://www.listbox.com/member/archive/rss/182180/21175430-2e6923be
Modify Your Subscription:
https://www.listbox.com/member/?member_id=21175430&id_secret=21175430-6a77cda4
Powered by Listbox: http://www.listbox.com
