[dm-devel] [Lsf-pc] [Topic] Bcache

Kent Overstreet koverstreet at google.com
Thu Mar 15 17:02:48 UTC 2012

On Wed, Mar 14, 2012 at 02:54:56PM -0400, Ted Ts'o wrote:
> On Wed, Mar 14, 2012 at 02:33:25PM -0400, chetan loke wrote:
> > But you are not explaining why dm is not the right stack. Just because
> > it crashed when you tried doesn't mean it's not the right place.
> > flash-cache works, doesn't it? flash-cache's limitation is because
> > it's a dm-target or because it is using hashing or something else?
> > There are start-ups who are doing quite great with SSD-cache+dm. So
> > please stop kidding yourself.
> SATA-attached flash is not the only kind of flash out there you know.
> There is also PCIe-attached flash which is a wee bit faster (where wee
> is defined as multiple orders of magnitude --- SATA-attached SSD's
> typically have thousands of IOPS; Fusion I/O is shipping product today
> with hundreds of thousands of IOPS, and has demonstrated a billion
> IOPS early this year).  And Fusion I/O isn't the only company shipping
> PCIe-attached flash products.
> Startups may be doing great on SSD's; you may want to accept the fact
> that there is stuff which is way, way, way better out there than
> SSD's which are available on the market *today*.
> And it's not like bache which is a new project.  It's working code,
> just like flash cache is today.  So it's not like it needs to justify
> its existence.
> Best regards,
> 					- Ted

Thanks Ted, as usual you word things rather less abrasively than me :)

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