Top Solid State Disks and TB Drives Reviewed

Lucas123 writes "Computerworld has reviewed six of the latest hard disk drives, including 32GB and 64GB solid state disks, a low-energy consumption 'green' drive and several terabyte-size drives. With the exception of capacity, the solid state disk drives appear to beat spinning disk in every category, from CPU utilization, energy consumption and read/writes. The Samsung SSD drive was the most impressive, with a read speed of 100MB/sec and write speed of 80 MB/sec, compared to an average 59MB/sec and 60MB/sec read/write speed for a traditional hard drive."

Longevity of NAND flash

[ASkGNet]

NAND flash deteriorates with use. When used in a high-I/O situations like hard drives, just how much time will it be able to work correctly? If I recall correctly, NAND blocks are guaranteed to the order of 100000 writes.

Reliability

[RonnyJ]

It's not mentioned in the summary, but added reliability might make these types of disks more appealling too:

The no-moving-parts characteristic is, in part, what protects your data longer, since accidentally bumping your laptop won't scramble your stored files. Samsung says the drive can withstand an operating shock of 1,500Gs at .5 miliseconds (versus 300Gs at 2 miliseconds for a traditional hard drive). The drive is heartier in one other important way: Mean time between failure is rated at over 2 million hours, versus under 500,000 hours for the company's other drives.

Re:Longevity of NAND flash

[peragrin]

Yes, new on disk topology mappings, and new tech give you roughly a million r/w and the mappings help to evenly distribute the load.

Re:Longevity of NAND flash

[plague3106]

This is always claimed as the solution, "evening" writes. But I think the question about how long will the drive last is still relevent; all it takes is a mostly full disk, which has a high I/O load. Even with evening, it seems that at least part of the disk can fail before the rest of the disk.

Do traditional drives fail if the same sector is written to over and over again as well?

Re:Hmm

[jandrese]

No, no reasonable people can afford them yet.

Re:MTBF/Write Cycles

[everphilski]

Meaning on a 32GB Drive, before you start seeing failures, you would have to (thanks to wear-leveling) write 32*100,000 GB, or 3.2Petabytes

NOT true, unless the drive is completely empty! If you have 31 gigs of data on that drive which you were using as long-term storage, then you'd only have to write (32-31)*100,000 GB of data before failure. You obviously wouldn't be overwriting any data already stored on the drive ...

Waiting for low-end drives

[alegrepublic]

I am still waiting for a reasonably priced low-end drive. An 8GB usb drive [buy.com] can be found for about $50. Packing 4 of them and replacing the usb circuitry with SATA would make for a 32MB for $200. Granted, it may not be the fastest drive around, but sometimes speed is not the most important factor. A 32MB would be enough for installing any current OS and still have some room for personal files to carry along on a trip. So, I think the current trend of providing high-end drives only is just an attempt to milk users to the maximum without much concern for what we actually need.

Re:What about real performance

[KonoWatakushi]

No need to compare with 15k rpm drives; flash disks lose spectacularly to low rpm laptop drives for random write performance. For obvious reasons though, no one ever tests random write performance. Manufacturers also rarely report random write IOPS.

Flash is great, if your disk is basically read-only.

Then don't fill the drive

[tepples]

This is always claimed as the solution, "evening" writes. But I think the question about how long will the drive last is still relevent; all it takes is a mostly full disk, which has a high I/O load.

Easy: don't let the drive become mostly full. This means heavy-duty drives will be a 64 GB chip reformatted for 48 GB with the rest designated as spare sectors for wear leveling, but the power consumption and seeking speed benefits can still make it worthwhile.

Re:Longevity of NAND flash

[zeet]

So you're saying that you lost 42kb of data you did care about, and some other unnamed amount of data that you lost but didn't care about? That seems a bit disingenuous. Even if you could have recovered the other data, since you didn't try it wasn't recovered.

Re:Swap partition/file

[johannesg]

Why not just buy enough RAM? It is cheaper than using a solid-state disk, and if all you use it for is swap anyway it really doesn't matter if it volatile or not...

Re:Longevity of NAND flash

[TooMuchToDo]

I can understand your reluctance to trust flash media. Indeed, it hasn't been proven like spinning media has. Let's take another example. An in-car radio. I want a 100GB hard drive in my car, solid state, that is for all intents and purposes write once. I should be able to dump 10s of GBs of MP3s onto it, and the index should be stored on a replaceable CF card (as the index would be changed often). But why would I remove music from the drive? I can just add more music.

For the above example, a flash drive works very well. If you need the benefits of flash storage mediums (vs spinning media) you should be prepared to engineer around the situation. Run temporary data out of RAM with battery backup, and only commit the data to flash between reboots and power outages.

Re:MTBF/Write Cycles

[orclevegam]

Well, it may not entirely negate the effectiveness of wear leveling, but it definitely makes the calculations a bit more complicated. Lets look at the theoretical example of a 32G disk with 31G used and a 512M write about to happen. It decides that the free space already has too many writes, and it needs to write the data to a used section of the disk instead, so it finds a 512M chunk of data that has the lowest write count and copies that to the free space (with a high write count, further increasing it's write count). It then takes the new chunk of data and overwrites the old chunk of data (once more increasing a 512M blocks write count). Now, there's only two issues here. First, even though you've moved some data which you hope is going to be semi-permanent (as it had low write counts) to a high count section, there's no guarantee that the user won't turn around and delete those files in the next couple minutes making it pointless to have copied the data there. Second, to write 512M of data, you've just had to perform 2 512M writes thus using twice the cells to store the actual content. Yes, following this strategy should increase the time till you see a failure, but it also invalidates the simplistic calculation used to come up with the 50+ years till failure figures some people have proposed. Now, I'm not saying the performance won't still be a long time, just that it's not as cut and dry as it might seem.

Re:Longevity of NAND flash

[s_p_oneil]

"all it takes is a mostly full disk, which has a high I/O load"

It is a relevant question, but this wouldn't kill your hard drive, it would simply reduce the amount of free disk space. And it's not difficult to imagine a file system smart enough to move files around when this happens. When a sector gets written to too many times, it can simply look for and move a really old file onto that sector to free up some of the rarely used sectors of the drive. With the increased performance of SSD, you probably wouldn't even notice it.

Aside from the re-write issue, flash memory drives should be WAY more reliable than a mechanical HD. It should never just completely die or start getting bad sectors so fast you don't have time to retrieve your data. It should also be a lot easier to replace when it starts to degrade. It shouldn't be as susceptible to damage when you drop it from a height of 3-5 feet, or due to heat, cold, vibration, dust, humidity, etc. I'm not sure whether a magnetic field could erase it like a hard drive, but if not, that's another plus for SSD. I imagine SSD's are more susceptible to static electricity, but so is almost everything else plugged into your motherboard, so I'm not sure if that could be considered a minus.

I'm sure if you ever tried an SSD on a laptop, you'd never want to go back to an old HD. The improved performance and battery life would make going back to an old laptop HD seem like going from broadband back to an old 56K modem.

Re:With the Exception of What???

[Bacon Bits]

So why not move to mag tape?