From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <6cbc566e63d124cdbc8191a6060c2e6f@quanstro.net>
From: erik quanstrom <quanstro@quanstro.net>
Date: Sat,  7 Mar 2009 08:58:42 -0500
To: 9fans@9fans.net
In-Reply-To: <20090307060057.GA65761@mero.morphisms.net>
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Subject: Re: [9fans] threads vs forks
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On Sat Mar  7 01:02:31 EST 2009, jkw@eecs.harvard.edu wrote:
> On Fri, Mar 06, 2009 at 10:31:59PM -0500, erik quanstrom wrote:
> > it's interesting to note that the quoted mtbf numbers for ssds is
> > within a factor of 2 of enterprise hard drives.  if one considers that
> > one needs ~4 ssds to cover the capacity of 1 hard drive, the quoted
> > mtbf/byte is worse for ssd.
>
> That's only if you think of flash as a direct replacement for disk.

i think that's why they put them in a 2.5" form factor with a standard
SATA interface.  what are you thinking of?

> SSDs are expensive on a $/MB basis compared to disks.  The good ones

not as much as you think.  a top-drawer 15k sas drive is on the order
of 300GB and $350+.  the intel ssd is only twice as much.  if you compare
the drives supported by the big-iron vendors, intel ssd already has cost
parity.

> For short-lived data you only need go over the I/O bus twice vs. three
> times for most NVRAMs based on battery-backed DRAM.

i'm missing something here.  what are your assumptions
on how things are connected?  also, isn't there an assumption
that you don't want to be writing short-lived data to flash if
possible?

- erik