[luau] No hard drive, only compact flash card

[Matthew John Darnell]

----- Original Message ----- 
From: "MonMotha" <monmotha at indy.rr.com>
To: <luau at videl.ics.hawaii.edu>
Sent: Sunday, July 06, 2003 1:31 PM
Subject: Re: [luau] No hard drive, only compact flash card


> Matthew John Darnell wrote:
> > Aloha,
> >
> > Does anyone have any experience with booting and running an full Linux
> > server install from a 1.0GB CompactFlash Cardor similar.
> >
> > By full server install I mean, apache, sendmail, mysql, gc++, etc.  No X
> > needed, only command line.
> >
> > Seems like it would be possible, 500MB for the OS and 50MB for the apps.
> >
> > I wonder how fast/slow they are for access compared to a hard drive.
> >
> > I see 1.0GB card for $299 retail, they will only be getting
> > cheaper/faster/higher density.
> >
> > Aloha,
> > Matt
> >
>
> CF cards are *VERY* slow compared to hard drives, especially on writes.
My
> little 32MB things can manage about 1-4MB/sec reads, but only about
> 100-300kB/sec writes!  This is *REALLY* slow.  You will NOT want to even
THINK
> about swapping to it.  In other words, make sure you have enough RAM
because
> there won't be any swap.  RAM is cheap these days, so this shouldn't be a
> problem.  However, last time I checked, distros like redhat likes to
complain a
> lot if you didn't set up swap for them (I think it used to be that redhat
would
> refuse to install under such a situation?)
>
> People tend to overexagerate the erase cycle limitations of flash.  CF
cards
> usually do wear patterning to prevent the same sectors from being used
over and
> over, and when they have reached their max usage, that sector is just no
longer
> used and is remapped (like bad sectors on IDE hard drives).  The entire
card
> isn't useless.  If you're really concerned about this, you can get nicer
flash
> cards that actually present themselves as raw flash, rather than ATA
flash, and
> run a real flash filesystem like jffs2 on it. jffs2 includes on-the-fly
> compression (which I think can be disabled, but may actually help with
> read/write speed in this case), and all the bad block handling/wear
patterning
> you could need.

I was told once the "best" minimalist distro was debian.  I sure like the
functionality of apt-get.
An IDE to flash adpater runs about 30 bucks, a lot less than I thought it
would.

> However, due to their slowness at writes, I'd reccomend keeping really
dynamic
> things like /tmp in a ramdisk (use tmpfs, it takes up only as much ram as
it
> needs to based on what's in it).  You might also want to do something with
/var
> (like unpacking it to a ramdisk at startup, then tarring it up back to CF
at
> shutdown, of course this makes unclean shutdowns REALLY bad).  Or, you
could
> just not have logging to /var/log and simply use a ring buffer like is
used by
> busybox's syslog.

I will have to research jffs2 and busybox.

> I'm still curious if even 500MB would be needed for "the os".  You seem to
be
> used to very bloated desktop oses (like redhat) that are designed to have
> everything abstracted two or three times (remember, you can always fix the
> problem by adding another layer of indirection).  I will say that I have
"the
> os" in well under 4MB (where "the os" is defined as kernel, core apps like
stuff
>   in /bin and /sbin, and libraries like glibc in /lib; this does not
include
> /usr of course).  Aagin you can save a fair amount on smaller systems by
playing
> tricks with smaller versions of libraries, but on a system with full apps
like
> mysql and gcc, it won't be worth it (as I think gcc completely and utterly
> requires glibc).
>
> Toolchains are big, but they're not that big.  I've seen full x86->ARM
> toolchains in about 50-70MB.  But that has to include all the foreign
libs.
> Here, those would be considered part of "the os" or "the apps", depending
on
> their usage, since they are needed to run stuff locally anyway.  The
static libs
> will sometimes pose problems because they tend to be rather large, but at
least
> headers are usually pretty small :)

4MB!?!? with all the important apps?  I have seend Linux on a floppy but
they were so very limited.  I think that is incredible.
I will buy one of the converters and try a small install of debian, I
already have a 256MB flash card.

I am very suprised no one sells PC like this.  All of the ones I found were
cash registers or the like, no general purpose PC's.  I would think this
would be great for routers, firewalls, etc.  High high availabilty stuff.

Thanks,
Matt