[OmniOS-discuss] OmniOS based redundant NFS

Bob Friesenhahn bfriesen at simple.dallas.tx.us
Fri Sep 29 22:55:40 UTC 2017

On Fri, 29 Sep 2017, sergey ivanov wrote:

> Thanks, Artem, it is a very good list of suitable hardware!
> I have a question about ZIL.
> I read that SSD for it should be about 8G. I did not see more than one
> gigabyte allocated for ZIL on our servers. Can you comment it?

It only needs to be large enough to contain the maximum amount of 
synchronous write data to be committed in one transaction group. 
This means that it is dependent on the I/O performance of the primary 
storage devices in the pool, the amount of main memory, and the 
maximum time allowed without writing a transaction group, all of which 
are factors when deciding when a TXG should be written.  The amount of 
data to be stored also depends on how large the synchronous writes are 
since large writes (e.g. 128k) by-pass the dedicated ZIL and go 
directly to main store.

If there was one TXG per second, then the 8GB SSD would provide for 
almost 8GB of synchronous writes per second (assuming that writes are 
small), which is quite a lot.

Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

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