hard drives vs flash drives vs hybrid

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giantjoebot

Senior member
Jan 6, 2007
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I keep seeing these claims that flash storage is faster than hard drives. In fact, I just saw an offer on newegg where if you sent over like $200 on AMD or ATI products you got a free flash drive that uses the new technology in Vista that is meant for hybrid drives. It stated that flash storage can be accessed much faster than a hard drive. But is that true?

Its my understanding that the transfer rates of flash storage is much slower than that of a hard drive, and the purpose of the hybrid drives is for laptops because flash storage is less volatile than hard drives. By using flash storage in a hybrid drive the platters have to be accessed less, which reduces the chance of the drive failing. But this is because laptop get moved around a lot, and can possibly be moved while the hard drive is in use.

Now for the transfer rates. My WD 250gb SATA2 7200rpm drive with a 16mb cache benchmarked in sandra as having a transfer rate of 60MB per second. From what I have read USB flash drives and even SD flash storage connected through a IDE adapter get anywhere from less than 20MB per second to around 30. So how is this faster? I can see where this might be closer to a 4200rpm or 5400rpm laptop hard drive, but the claims that I always see never state which drives they are comparing too.

I think the key word here is "accessed". While the transfer rates of flash storage is much slower, the access time is suppose to be 100 times faster. So with small amounts of data flash storage should be much faster, but much slower when it comes to large amounts of data. So I could see how a hybrid drive could be faster than a regular drive, if its done right. If in some way they design the drives to only use the flash storage for small amounts of data. Personally I think that this is a play on words that actually deceives people into thinking that flash storage performs better than hard drives, when in fact in many circumstances it doesn't.

So what do you guys think? Which is the faster storage type? Will hybrid drives be better than regular drives, or will we only see them in laptops?
 
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dnoyeb

Senior member
Nov 7, 2001
283
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I am going to guess that the SATA protocol is faster than the USB Protocol. As for the technologies themselves, sure, memory of all forms is probably faster than a spinning disk. Of course, lots of HD these days come with a cache on them whose access time is likely faster than the flash technology.

Sure flash is a faster technology than a HD, but its slower than EEPROM or RAM. Anyway, flash technology can not handle the number of writes HD can handle. No where near the number. So you don't want to use a flash drive as if it were a HD because you will wear it out. However, with this knowledge, you may not care if it wears out since they are cheap and convenient.

I don't see the benefit of a hybrid drive. Either your stuff is safe, or its not.
 
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pm

Elite Member Mobile Devices
Jan 25, 2000
7,419
22
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There's two parts to speed: latency, and transfer rate (ignoring writes for this discussion).

Hard disk (using 74GB WD Raptor 10krpm for reference)
transfer rate: 62.9MB/s (storagereview.net)
read latency: ~7.2ms (storagereview.net)

Flash (used 150x SD flash card for reference):
transfer rate: 22.5MB/s (manufacturer's spec)
read latency: ~1ms (measured via USB SD-card reader)

So, the Raptor has about 300% higher transfer speeds compared to the Flash card. But the SD card has about 700% faster latency.

If you are streaming data off of the disk/card, the transfer rate will dominate, whereas if you are randomly pulling data off the disk/card from a variety of locations, the latency will begin to dominate. For booting a computer to Windows XP, Flash disks will be faster. For copying one massive file from one drive to another, the hard disk will be much faster. There is no clear "winner" here - in some cases, Flash will be much faster, in others, the hard disk will be.

The idea of hybrids is that you use the flash as a form of read cache to speed up accesses. The 16MB RAM caches that are commonly used on "regular" hard disks are faster in all respects compared to flash, but the flash sizes that are being quoted for hybrid drives are 256MB ( http://www.samsung.com/Products/HardDiskDrive/HybridHDD_Flashon/index.asp ) or 16x larger than the RAM sizes. The nice thing about hybrid disks is that you should get a nice speed increase (still to be seen, but it looks good on paper). By using flash as a cache, the drives avoid the problems that flash memory have - high cost per MB, long-term reliability, slow erase and write speeds. Readyboost for Vista uses Flash similarly - essentially using the flash as a form of large cache for frequent accesses - in some cases people have reported fairly large speed-ups when using Readyboost - particularly when the system is low on usable memory.

Over the long term, PCM (phase change memory) is likely to replace Flash in the next 5 years. PCM should have better read transfer rates compared to Flash (it should be more comparable to NOR flash, as opposed to NAND flash used in SD cards and the like) and it should have better longevity and write speeds compared to Flash for a similar cost to NAND flash. So, later this year we should expect the first PCM memories to start to appear, and I would think in 2-5 years, PCM should take over the solid-state drive area and it should have even more favorable characteristics to be used in ever larger hybrid drives.
 
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giantjoebot

Senior member
Jan 6, 2007
205
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I mentioned the latency. And I agree with what your saying. I just think that blunt statements that one is better than the other is wrong, they both have their own strong and weak points. Some of the statements that I have read sound to me as though they favor the flash storage. Of course these are generally statements made by people trying to push flash storage, so of course they are going to be bias in their statements. I just want to clear things up, mostly in my own head.

It would seem to me that mainly disks with the OS installed on it would benefit the most from hybrid drives. I don't think the large span of drive on my media server would benefit at all from a hybrid drive since it mostly stores video. I wonder how hybrid drive will affect the market. Hopefully they won't cost a ton, and maybe they will drive the prices down on regular drives.
 
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thutmose3

Member
Feb 18, 2007
31
0
0
Well if you look at NAND drives, the transfer rate is 62 Mb/s, which is a little less than a Raptor. Also, they are a fraction of the size of a normal drive (1.8 in) and have no moving parts, greatly reducing power consumption and heat. They are really expensive right now, but they would be invaluable to laptops, allowing more power to be alloted to the processor and peripherals or increased battery life. I think all of this is right, got it mostly from here...

http://www.computerworld.com/action/art...leBasic&articleId=9011969&pageNumber=2
 
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Lord Banshee

Golden Member
Sep 8, 2004
1,495
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those drives that have 62MB/s i think is using some kind of raid idea inside the drive. I do not think there is any flash memory that has those kinds of speeds. But overall i see nothing wrong with using some logic inside the drive to do this what ever works. But it will cause some delays for the logic and cost of the device doing the logic. I see it like the AMD vs Intel about a "True Quad Core" vs "Intels Quad Core" if it doesn't affect performance and it works the consumer does not care how it work.

Personally i am ready for SSD drives, HD technology has been around too long enough i can't wait for these true performance SSD drives that cost under 500 dollars.... 2008/09 maybe.
 
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