Re: WAPBL vs. lfs?

[Thor Lancelot Simon <tls%rek.tjls.com@localhost>]

On Tue, Aug 26, 2008 at 02:30:20PM -0700, Christopher Chen wrote:
> On Tue, Aug 26, 2008 at 1:45 PM, Aaron J. Grier 
> <agrier%poofygoof.com@localhost> wrote:
> > On Mon, Aug 25, 2008 at 11:47:18AM -0400, Thor Lancelot Simon wrote:
> >> The real fix for the "writes metadata twice" issue is to support a
> >> journal on another partition.  With a real SSD (that is, one that's
> >> not built from flash memory with its insane write penalty) this would
> >> make the extra writes almost free.
> >
> > prestoserve!
> 
> YAY!
> 
> Do you actually have one?

There's at least one vendor ("vmetro") of very large PCI NVRAM cards,
including some models with flexible DMA engines that allow device-to-device
transfers.  I asked a few years ago about obtaining a card and documentation
to write a NetBSD device driver and all was going well until after a few
back-and-forth messages, a _very_ onerous NDA came over the fence -- one
which would have prohibited including the resulting device driver in NetBSD.
I don't think this was intentional, but I just didn't have time to chase the
issue around with their lawyers, and so -- my own fault really -- I let the
thing drop.

These cards are *not* cheap.  Solid-state disks with SAS or SATA interfaces
are likely to be a lot more cost-effective.  What would really rock would
be firmware for one of the NVRAM-equipped RAID controllers that allowed
small volumes to be created which existed only in the controller NVRAM.
I was discussing _that_ with an engineer at Mylex when they were eaten
by several other companies in quick succession and, again, nothing came
of it -- too bad.