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explain 'sequential' vs 'random' memory read/write speed?

post #1 of 3
Thread Starter 
Hi!

Upgrading to a larger/newer/faster ssd.

I'm looking at the 250gb 840 vs the 256g 830 in particular. I missed out on some good deals on both of them, but right now, I can at least get the 840 for $165 and the 830 for $175 (shipped).

Now, here's what I don't know what to make of.
The 840 has TWICE the random write speed of the 830, but HALF the sequential write speed. I don't know the technicalities of why that is...
but even more fundamentally, I don't know what sequential vs random actually means in the real world?

The lifespan of the tlc nand in the 840 ought not to be a concern for my usage habits, btw. Someone did calculations that even rewriting 50gb/day would only kill the drive at 6yrs. I figure I'll leave it 2/3 full, and personally, only rewrite 5gb/day on average.
I don't know how often the microsoft page file, at 15gb in size last I looked, rewrites itself; and I don't know how many gb might be rewritten in a couple of hours of gaming. So maybe I'm actually rewriting 25gb/day without realizing it. So the tlc nand will die in 12yrs in such a scenario... not likely an issue!

Here's how I use my computer:
I install a game,
and I play it.
I also browse the internet. Video/photo editing, none at all.
Lots of first person shooters/adventure/story based games like far cry or dishonored or mass effect.
Also played some civ5, and some sims3, which seem like they might make quite a lot more use of memory than a shoot'emup.

File transfers? Not so often-- and never where speed would matter. I can stand to wait a couple hours for my roomate's 500gb of pirated anime to transfer onto my drive. Actually, that isn't going on the ssd anyway, that goes onto the 1tb disk drive. so nevermind.

Everyone seems to love the 830; but would the 840's much faster random write speed be much faster for how game files might operate?

The fundamental confusion, again, lies in that I do not know whether playing civ5 or sims3 is going to perform based on random write speed, sequential write speed, or maybe only read speed is the limiting factor at all (in which case the 840 is still modestly faster).

I'm leaning towards the 840; it seems to perform faster than the 830 in everything except sequential write speed, and it has the newer controller with twice the sdram cache and faster sdram too (although... I actually have no idea what that means either, heh).
If sequential write doesn't matter for gaming, 840 it is? If it actually matters a lot, 830 then?


thanks!
Edited by berninicaco3 - 3/23/13 at 1:00am
post #2 of 3
Thread Starter 
btw, I have a sata ii motherboard and am not likely to upgrade from it unless it's dirt cheap.
again, somewhat unclear on what that might mean for gaming (not bulk file transfers)... if speeding up a game means accessing data very quickly, but not necessarily a lot of it (like more than 3gb/s), then sata ii won't be a restriction, correct?

separate but related question... if sata ii IS a restriction that would limit read/write speeds above some threshold, maybe I should be looking at neither of these drives and aiming cheaper still?
post #3 of 3
Sequential memory read/write you can think of like this:

- is a read
* is a write.

Sequential is all in the same area of memory, kinda like filling up a book shelf, one row at a time, so like this:

*******
*******
*******
*******

Same for read



Random is just that, random. Because memory (and even SSDs) are electronic, not electromechanical like a hard drive, they are able to do random read and writes at very high speeds. You can think of this as reading books randomly, with no order for a book shelf. Write is putting the book back.

Games don't really need to do anything as far as random read/write. Random reads and writes would be when you have 30 people accessing random files all at the same time. The same would be for programs. Games are large chucks of data that are read from the drive and loaded into memory (mostly). There is some randomness, but once the game is loaded (or level is loaded), there aren't really any issues as far as performance goes.


EDIT:

If you go with an SSD for gaming, the only difference you will see is load times, opening apps faster, OS loading quicker. You won't be getting any more FPS out of it. That is why I went with a 1TB drive for my games. I don't care about load times, because once the game is loaded, I don't have problems.
Edited by Lord Xeb - 3/23/13 at 11:11pm
 
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Gsvlip Dudyrm
(15 items)
 
Oda'maksv
(9 items)
 
CPUMotherboardGraphicsRAM
3770k @ 4.5 1.312 load Zotac Z77 ITX Wifi GTX 1070 Gaming 2126/2249 w/ Hybrid cooler TridentX 16GB 2400MHz 
Hard DriveHard DriveCoolingCooling
Samsung 850 Pro 1TB Seagate 2TB H105 EVGA Hybrid GPU cooler 
OSMonitorKeyboardPower
Windows 10 Asus MG279Q - 24" 144Hz 1080p Filco Majestic II w/ Cherry Reds Seasonic X 760W 
CaseMouseMouse PadAudio
Bitfelix Prodigy Logitech G400 Razer Goliath AKG A701 
AudioAudio
JDS Labs Objective 2 JDS Labs ODAC 
CPUMotherboardGraphicsRAM
Core i5 750 3.99 (190x21) 1.376v Load ASUS P7P55d-E Pro GTX 670 FTW <- Poor overclocker :( 8GB (4x2GB) G.Skill DDR3 1600 
Hard DriveHard DriveOptical DriveOS
Samsung 830 Evo 128GB 2x 2TB  Some DVD drive OSX 10.10.4 
MonitorPowerCaseMouse
Asus 1080P Crap TX 750 HAF 922 G400s 
Mouse PadOther
Apple Keyboard Xbox One controler 
CPURAMHard DriveHard Drive
C2D 2,26GHz under volted @ .978v 8GB  Crucial M4 64GB SSD 500GB Scorpio Black 
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