- Subject: Re: [Lsf-pc] [Topic] Bcache
- From: "Ted Ts'o" <tytso@xxxxxxx>
- Date: Wed, 14 Mar 2012 14:54:56 -0400
- Cc: linux-scsi@xxxxxxxxxxxxxxx, Kent Overstreet <koverstreet@xxxxxxxxxx>, dm-devel@xxxxxxxxxx, nauman@xxxxxxxxxx, lsf-pc@xxxxxxxxxxxxxxxxxxxxxxxxxx, Vivek Goyal <vgoyal@xxxxxxxxxx>
- In-reply-to: <CAAsGZS5UTrYTbncAjk1Vor6R_-KWDboTw3sh+jXCbXm5q_o-TA@mail.gmail.com>
- Mail-followup-to: Ted Ts'o <tytso@xxxxxxx>, chetan loke <loke.chetan@xxxxxxxxx>, Kent Overstreet <koverstreet@xxxxxxxxxx>, Vivek Goyal <vgoyal@xxxxxxxxxx>, lsf-pc@xxxxxxxxxxxxxxxxxxxxxxxxxx, nauman@xxxxxxxxxx, linux-scsi@xxxxxxxxxxxxxxx, dm-devel@xxxxxxxxxx
- References: <20120314133228.GA2284@dhcp-172-18-216-138.mtv.corp.google.com> <20120314155339.GC30235@redhat.com> <CAAsGZS6Jw8xCdu3Wuve=iaKpd_UNdm72kbTbiQtypAfrZ46PWw@mail.gmail.com> <CAH+dOx+Vgv12w=Q=8hCQggLg+kq6TnT2i3ZtnpZ=bNVyMgk31Q@mail.gmail.com> <CAAsGZS5UTrYTbncAjk1Vor6R_-KWDboTw3sh+jXCbXm5q_o-TA@mail.gmail.com>
- Reply-to: device-mapper development <dm-devel@xxxxxxxxxx>
- User-agent: Mutt/1.5.20 (2009-06-14)
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
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