Re: [RFC] [DONOTAPPLY] [PATCH] enhanceio: STEC EnhanceIO SSD caching software for Linux kernel

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Feb 01, 2013 at 05:25:29PM -0800, Kent Overstreet wrote:
> Also, where's the end user documentation?

I was trying not to explode this patch's size, since the doc can go straight
into Documentation/ without as much fuss as, say, the ~1600 checkpatch
warnings and all the other comments we'll have about the source code.

> On Fri, Feb 1, 2013 at 5:23 PM, Kent Overstreet <koverstreet@google.com> wrote:
> > On Fri, Feb 1, 2013 at 4:57 PM, Michel Lespinasse <walken@google.com> wrote:
> >> On Fri, Feb 1, 2013 at 4:44 PM, Darrick J. Wong <darrick.wong@oracle.com> wrote:
> >>> This is a patch to migrate STEC's enhanceio driver out of their github
> >>> repository and into the staging tree.  From their README:
> >>>
> >>> "EnhanceIO driver is based on EnhanceIO SSD caching software product developed
> >>> by STEC Inc. EnhanceIO was derived from Facebook's open source Flashcache
> >>> project. EnhanceIO uses SSDs as cache devices for traditional rotating hard
> >>> disk drives (referred to as source volumes throughout this document).
> >>> EnhanceIO can work with any block device, be it an entire physical disk, an
> >>> individual disk partition,  a RAIDed DAS device, a SAN volume, a device mapper
> >>> volume or a software RAID (md) device."
> >>
> >> What's your take on the benefits of this vs bcache ?
> >
> > I've been trying to review it it for cache coherency and consistency
> > wrt. power failures, but the complete lack of high level documentation
> > is making that difficult.

Agreed. :/

> > I saw some benchmarks the other day where on writes EIO was faster
> > than the raw device, which was... suspicious.

Hmm, I haven't seen /that/, but then I wasn't specifically looking for it
either.

--D