Why first-generation flash SSDs are a bit disappointing

I’ve been waiting with anticipation for flash-based SSDs to come out. If you’re unfamiliar with these, they’re hard drives with no moving parts, so their life expectancy is 10 years, and they’re quiet, run cool, and they have virtually no seek time so for some tasks they’re lightning fast.

The best drives on the market, from what limited information is available, seem to be the Samsungs.The problem is that these drives have a sustained read speed of 50 MB/sec and write speed of 27 MB/sec. Under ideal circumstances, a conventional hard drive can exceed those numbers–especially the write speed. So what’s going on?

The main reason is that these drives have no cache on them. Conventional hard drives have a small amount of RAM that acts as a buffer between the computer and the platters. Today a budget drive has 8 megs of RAM. A lot of high-performance drives have 16, and I’ve even seen some that have 32.

The most frequently used data can come off this buffer at high speed. Writes can go to the buffer and the computer can get on with life, and the drive can write the data to the platters when it gets less busy. The other advantages of a solid state disk often can make up the difference when reading data, but if you’re writing a lot of data, the conventional hard drive wins the race most of the time.

SSDs could benefit from cache for one good reason: conventional RAM chips are still much faster than flash memory.

Now for the good news: I’ve read reports that the Samsung drive can boot Windows in 15 seconds and most common applications have single-digit load times. So if you don’t do a lot of writes, these drives can give you a performance boost.

The other complaint is capacity. You can pay $400 for a 32 gig SSD, which is more than you’d pay for a full terrabyte of conventional storage. For some people, this is a problem. Given the work I usually do these days, 32 gigs is plenty for me, and I could probably find ways to get by with 8. I just don’t keep a lot of huge data files around. But if I needed acres of data storage, I could load the operating system and my most critical apps on the SSD, and use the conventional drive for storage.

The old knock on flash memory was its finite lifespan. Put Windows’ swap file on a flash drive and let it run, and theoretically you could wear out the memory in a matter of days. And that’s always one of the first comments that shows up when the topic of flash drives comes up on sites like Digg and Slashdot. But today’s flash memory sustains more writes than the old stuff did, and newer drives use a technique called wear-leveling, where it distributes writes amongst the available chips. This technique makes the chips last a lot longer now, to the point where one respected tech journalist, Dan Rutter, actually recommends putting flash drives in old laptopos with maxed-out memory for the express purpose of holding a swap file. And Macintosh users have been using flash disks to soup up old Mac laptops for several years now. Flash disks give obsolete laptops a boost in both speed and battery life while reducing noise and heat, and it’s pretty safe to say that current technology allows a flash drive to last 3-5 years when used for this purpose, which is about as long as a conventional drive.

My next major system upgrade will probably be a Samsung SSD for at least one of my computers. It’d make a fantastic upgrade for my laptop, at the very least. The laptop will run faster (the hard drive in it is several years old, and I think it runs at 4200 RPM) and the battery life will improve considerably. I also like the idea of having a super quiet, cool-running desktop for the family room. But I definitely hope the second-generation SSDs will include some cache. Otherwise, there’s not much advantage to them over the old trick of buying a large, high-speed Compact Flash card and an IDE-CF adapter (Addonics is one source of these), as long as both the card and the adapter support UltraDMA.

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