Re: Plan: journalling fixes for WAPBL

[<Paul.Koning%dell.com@localhost>]

> On Sep 28, 2016, at 7:22 AM, Jaromír Doleček <jaromir.dolecek%gmail.com@localhost> wrote:
> 
> I think it's far assesment to say that on SATA with NCQ/31 tags (max
> is actually 31, not 32 tags), it's pretty much impossible to have
> acceptable write performance without using write cache. We could never
> saturate even drive with 16MB cache with just 31 tags and 64k maxphys.
> So it's IMO not useful to design for world without disk drive write
> cache.

I think that depends on the software.  In a SAN storage array I work on, we used to use SATA drives, always with cache disabled to avoid data loss due to power failure.  We had them running just fine with NCQ.  (For that matter, even without NCQ, though that takes major effort.)

So perhaps an optimization effort is called for, if people view this performance issue as worth the trouble.  Or you might decide that for performance SAS is the answer, and SATA is only for non-critical applications.

	paul