How feasable is a RAIF (Redundant Array of Inexpensive Flash media) on a T40 Laptop?

November 24, 2011 3:47 PM

How would placing two (or more!) Compact flash drives in my T40 laptop and using them as a striped RAID 0 compare to installing an equivalent (PATA) SSD? Is there some other thinking-further-out-of-the-box way of getting lightning-fast disk performance into a Pentium M-class laptop?

(For the sake of avoiding well-meaning comments, I know RAID 0 sets your RUNNING_WITH_SCISSORS=TRUE and will take appropriate precautions. )

I've reinstalled on the older 40GB drive in this machine after my previous question. It's loud and my battery life has been cut almost 25% since I reinstalled the hard drive(Was running with a USB Puppy install previously)

Looking at the pricing for PATA SSDs, it seems there are some congruence points where you would only pay slightly more for multiple CF drives of a given speed(*) and a similar total capacity (ex: two 32GB CF cards, vs a 64GB SSD)

The T40 is (in theory) capable of hosting up to six CF cards - Two in the PATA drive slot(master/slave), Two in CardBus adapters, two more in a PATA adapter placed in a ultrabay PATA adapter - Though most of the HOWTOs I read Back In The Day put a big NO stamp on raid across master/slave IDE combos because of bad performance due to drive switching issues - Is this also true for the CardBus slots, and does it still hold true when using solid state media?

I think there are several bottlenecks here (CardBus controller, PATA controllers, internal PCI bus, heck the Pentium M 1.5ghz chipset), but I'm not sure at all which are the narrowest.

(* - I know the specs lie, I'm just using them to try and achieve some sort of apple-to-appleness.)

posted by Orb2069 to Computers & Internet (7 answers total)

In my experience, getting decent write speeds out of flash-based media requires a controller designed with that as a primary goal. I would expect that you'd find the in-practice write speeds on a general-purpose CF card extremely disappointing compared to what a decent SSD can deliver, and I would not expect striping a bunch of CFs to lift that speed enough to make it worth the trouble.

I'd also expect the wear-leveling logic in a CF controller not to work as well as its SSD counterpart, and would expect a CF card exposed to typical OS system drive write patterns to fail relatively quickly.

All that said: I haven't actually tried anything like the setup you're suggesting, and would be interested in finding out whether my expectations line up with reality.
posted by flabdablet at 4:13 PM on November 24, 2011

Best answer: Just an FYI, I tried doing something like this a few years ago and I found that Windows wouldn't let me have the OS itself on a striped volume, if that's what you're planning. I can't remember if I was trying to do it with WinXP or Server 2003, though, newer versions obviously might be different.
posted by XMLicious at 4:24 PM on November 24, 2011

This is more money and effort than you should be throwing at a five-year-old laptop. Just buy the PATA SSD.
posted by mhoye at 4:53 PM on November 24, 2011

Your proposal is the kind of thing I would only suggest if you already have all the materials on hand as in a "what can I do with all these CF cards and adapters I got" situation. If you're going pay money, get a real SSD or a new cheap laptop.
posted by Edogy at 4:54 PM on November 24, 2011

I'm not an expert, but my understanding is that SSD drives are not like a flash card - they 1) have a lot more storage than their advertised amount, 2) use that storage in conjunction with some extra machinery to seamlessly check and move data to keep the bits safe as sectors go bad. (Flash bits can only be written a fairly limited number of times before going bad)

A flash card doesn't really seem like a comparable device. And given that this device WILL get bad sectors far more quickly and inevitably than a hard drive, using it in a RAID 0 configuration seems to me like just putting a gun to the laptop and shooting it with a delayed action trigger. A SSD drive comes with extra storage precisely so it can do exactly the opposite of that, because reliability is a big problem with flash memory rewrites.

If the drive is going to be used for read-only, then give it a go, but if the computer is going to be reading and writing, I think it's a bad idea - a lot of time and effort to make something that is very likely to fail. And Murphy's Law of computing is that drives always fail right when you need them, and when they have something important that isn't backed up.
posted by -harlequin- at 5:10 PM on November 24, 2011

Best answer: I did that with a similar vintage laptop. It was fast for some things, very, very slow for others. (Like, anything that was write intensive). A machine of that age probably uses a lot of shared busses, so you probably won't get anywhere near double the speed by using a striped set.
posted by gjc at 9:19 PM on November 24, 2011

This simply sounds ridiculous. Why go through all the trouble for what sounds like not-much-difference? Just get the SSD and be done with it.
posted by rhizome at 12:30 PM on November 25, 2011