[luau] No hard drive, only compact flash card

[MonMotha]

Mark Pettit wrote:
>>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.
> 
> 
> Given all of the limitations that have been described, I don't see how
> it's all that useful to use CF in a high-availability environment like
> a router or firewall.

You fail to realize how little hard drive usage a router has :)

My company, Computer Experts (www.comp-exp.com, call 317-833-3000 if you're 
interested), sells a router based on CF card (for either your PC or we're 
working with Single Board Computers these days as well) where the entire root 
filesystem is readonly.  Yup, that's right (not write :).  The entire root 
filesystem is never mounted readwrite.  /tmp is on a tmpfs.  /var can be mounted 
on a tmpfs if no hard drive is available for logging (and of course logs can be 
sent to another machine via standard syslog protocols).  /dev is mounted in a 
small tmpfs as well and populated from a small tarball.

The beauty of this is that you can actually treat it like a dumb router :)  Most 
people wouldn't think of "just unplugging" a Linux box when they have to move 
it, but with our product you can!  Because the entire fs is readonly, there's 
absoultely no issues with just unplugging it (other than losing state, which 
means all your connections will probably be reset if NAT is being used).

Sorry if this sounds like an advertisement (it kinda is), but it's a really cool 
device!  Did I mention all this is done off a 32MB flash card (so there's plenty 
of room for more functionality in the firmware...of course it already speaks SNMP).

> 
> PCs are cheap enough now that you can deploy a pair of fully-redundant
> PCs running Linux (or any other Unix-ish OS), on relatively fast hard
> drives, for a few hundred dollars.  Why would you do anything else?
> Why bother with the added complexity of CF?
> 

Added complexity of CF?  You must have never set up a set of fully redundant 
systems :)  I assure you, CF cards are far from complex!  They're standard ATA 
flash devices.  If you need to write to them, you can.  But they really shine in 
situations like a router because most stuff isn't hard drive bound (only admin 
activities, logging, and config changes require accessing the hard drive at 
all!) and they're VERY reliable.  Would you ever think of just dropping a hard 
drive on the ground?  If you did it by accident would you be likely to ahve 100% 
data recovery?  I've dropped tons of CF cards on the ground (and a computer one 
was in, d'oh!) before and they keep working fine.  Reapeat after me: No moving 
parts == good thing :)


Of course, CF cards aren't great for every day use.  Their write speeds are VERY 
slow, and their read speeds aren't exactly fast (well, they would have been 
about 10 years ago :).  Most situations will never hit the erase cycle limit, 
but there is always that concern as well in very dynamic environments (though 
Linux's fs cachcing can actually help quite a bit here with stuff that's REALLY 
dynamic like SQL databases, though I still wouldn't run an SQL DB on a CF card 
unless you could cache the whole thign in RAM).

--MonMotha