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HDD/SDD Definitions and their place in applications

post #1 of 3
Thread Starter 
Hey guys, I've been hearing terms like IOPS, Latency, Random I/O's, Bandwidth, Sustained Sequential Read/Write. I'm not sure I understand what they all mean and how they effect actual speeds of reading and writing. For instance, what makes a SDD better than a single 7200rpm HDD and for that matter, what makes a SDD better than 2 7200rpm RAID 0 HDD. Why wouldn't SDD in RAID 0 be the best? Why are SDD's apparently so much faster than HDD? And lastly, could someone REALLY explain what is best for different applications like gaming and productivity (I'm not interested in cost effective, I just want to know theory here). Where do they all fit into the market, because I understand they all have a purpose. Thanks in advance...I know I'm not the only one confused.
post #2 of 3
Hey man. It's not too hard on the surface, although the fine details are complex enough.

Basically there are several differences between SSD and HDD, but to answer your last question right off the bat: HDD's don't really have a place anymore. They are a dying tech that will be around for a while for two reasons:

1. The cost per GB/$ is still too high for SSD's to be a value.
As of October 2010, NAND flash SSDs cost about (US)$1.40–2.00 per GB.
As of October 2010, HDDs cost about (US)$0.10/GB for 3.5 in and $0.20/GB for
2.5 in drives.
2. HDD's are still better optimized for operating systems.
If you take a SSD and plug it into windows 7, it will score higher than a
traditional physical drive sure, but Windows won't set it up as best as possible.
There are still several things you as a user need to perform in order to ensure
longevity and sustained Read/Write speeds for your SSD.

All that being said, SSD's are faster. No debating it, but touching on my second point from a moment ago, they do not work well in RAID. This is because as SSD's placed into a Raid setup do not support TRIM. SSD write performance is significantly impacted by the availability of free, programmable blocks. Without TRIM enabled to reclaim those blocks, you force your SSD to rely on a technology called Background Garbage Collector (BCG for shorthand). Previously written data blocks that are no longer in use can be reclaimed by BGC or TRIM; however, even with TRIM, fewer free, programmable blocks translates into reduced performance.

The last statement touches on one of the biggest caveats of an SSD. When you buy a 120GB SSD, you DO NOT want to fill the entire drive. Rather you want to leave a piece of it unallocated as this will increase drive longevity. All traditional Hard Drives do not suffer from this, as you can write data to them infinitely until they fail for whatever reason. An SSD has a threshold that once crossed, the SSD will begin to fail. Typically that is about 5 years or so atm.


To sum the above all up, if you can afford two 512 GB SSD's for everything, have at. But the reason people choose a hybrid setup is primarily cost. Buy a 120GB or so SSD and use it for your Operating System and then RAID0 a couple physical dish hard drives for media and games.


Hope this helps!
    
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CPUMotherboardGraphicsRAM
[INTEL] i7 930, 4.4ghz @ 1.27V [Asus] Rampage III Extreme [Sapphire] 2X 6950's Flashed to 6970's @950/1425 [G.SKILL] Ripjaws X Series 12GB DDR3 @ 2133 
Hard DriveOptical DriveOSMonitor
[Crucial] 2X C300's in Raid0 & [Samsung] 2X 1TB F3 [Hewlett-Packard] DVD-RW [Microsoft] Windows 7 64-bit [Asus] 3X 23" LCD 
KeyboardPowerCaseMouse
[Microsoft] Sidewinder X6 [Kingwin] Lazer LZ-1000 [Xigmatek] Elysium (Being Modded) [Microsoft] Sidewinder 
Mouse Pad
[XTrac] Ripper 
  hide details  
Reply
post #3 of 3
Thread Starter 
Absolutely amazing reply, thanks so much for your fast and detailed response.
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