Just how big of a deal are IOPS, then?

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R

Reaps

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Aug 19, 2013
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Originally I was going to snap up a Samsung 840 Pro (PD256), but then I noticed the markedly cheaper 250 variants (TD250 and TE250)

The TD250 has a read/write speed of 530/240MB/s, whilst both the TE250 and PD256 have read/writes of 540/520. After struggling to find a difference between the latter two (apart from the PD256 having a WHOLE EXTRA 6 GIG WOO! for an extra $50), I came to the IOPS

So, yes, I went and had a read up on the difference between IOPS and read/write, but I'm still stuck in a purchasing quandary:

The PD256 ($AU258) is advertised as having a 4KB random read/write of 100,000/90,000 IOPS, whilst the TE250 ($AU209) has 97,000/66,000

So the big question is, is it really worth nearly $50* to pick up nearly 30,000 IOPS? I've seen people say that it "isn't noticeable from SSD transferring to SSD, but it is when it's SSD to HDD" Do they have that backwards? That doesn't make sense to me given how the low the IOPS and read/write speed of a HDD is compared to a SSD. Is it really a big deal? I'm guessing not, but then again ye olde 'what are you using it for?' comes into play; I'll be using one SSD as my 'C:\' drive for windows and assorted apps; the rest is all HDD

Hope I've given enough info on the situation for someone to clarify this for me. It took me long enough to discern a noticeable difference between the TE250 and the PD256 in the first place!

Cheers.

*$AU1 = about US91c, so yes, 50 bucks is a bit of a big deal.
 
Solution
rvilkman
Even the cheapest of the 3 is so above and beyond that of regular hard drives that if you intend to just use the drive as your boot and application drive the reads are what you are mostly interested in. The 240MB/s is quite enough to be snappy even for writing.

If you actually have data files that you are also writing on the SSD, doing some work or something then you might consider upgrading to the PRO. Otherwise there is very little use for it.

The EVO is a nice middle of the road piece with better durability included as pointed out above. So It would be a good choice if it's not much more expensive than the basic variant.
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Someone Somewhere

Someone Somewhere

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Sep 23, 2012
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In general, it doesn't matter once you've gotten an SSD - you're unlikely to max it out.

The main difference is that some are based on 2bpc NAND vs 3bpc (2bpc has more P/E cycles, so lasts longer), and is somewhat faster. 840 Pro is 2bpc, 840 and 840 Evo are 3bpc. You're very unlikely to run into the limit unless you're running DBs of them, though.
 
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rvilkman

rvilkman

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Even the cheapest of the 3 is so above and beyond that of regular hard drives that if you intend to just use the drive as your boot and application drive the reads are what you are mostly interested in. The 240MB/s is quite enough to be snappy even for writing.

If you actually have data files that you are also writing on the SSD, doing some work or something then you might consider upgrading to the PRO. Otherwise there is very little use for it.

The EVO is a nice middle of the road piece with better durability included as pointed out above. So It would be a good choice if it's not much more expensive than the basic variant.
 
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Solution
RetiredChief

RetiredChief

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1) On Sequencial performance - This is the least important matrix for an OS +Program files - Reason is that most of thes files are rather small. The Random 4 K is more important: However, read on.

2) Benchmarks are SYNTHETIC and used by reviewers to show differencies between the better SSDs, However seldom translates to real world diff. Case in Point:
I Have the 256 Gig Crucial M4, Smsung 256 gig 830 and Samsung 256 gig 840 Pro. Both the M4 and the 830 have an overall AS SSD score of mid 700's while the Samsung 840 Pro gets a score of 1100 (Hits 1200 on newer Intel chipsets). Going from 750 -> 1100 you would think there would be a very noticable performane gain in day-2-day useage - NOT.

3) You are correct SSD-> HDD transfers are limited by the HDD throughput.

4) Newer Samsung "value" SSDs use TLC while the 840 Pro uses Toggle NAND. Biggest diff is he Number of write cycles before the Cell dies. Normally not an issue as even the Lower rated TLC NAND shoul last the average user well past the point of replacing it with newer technology.
 
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R

Reaps

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Aug 19, 2013
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Thanks all for the replies, it's certainly cleared things up a little. Seems the Evo is the way to go, given the negligible price difference between that and the standard, and the noticeable difference between that and the Pro

Cheers again
 
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popatim

popatim

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If you plan on filling the drive then go with the pro. The EVO gains speed by using an unused portion of ssd as 2bpc cache nand so I have to beleive you will need even more overprovisioning then the pro version (ie - you wind up with more usable space with the pro) in order to stave off drive performance losses.

Also IOPS is directly proportional to drives overall speed.
iops*sector size= bytes per second
(66k*4k= 264Mb/s) random write (minus overhead.)
 
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popatim

popatim

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Overprovisioning
The portion of total NAND flash memory capacity held in reserve (unavailable to the user) for use by the FSP (Flash Storage Processor) is used for garbage collection (the major use); FSP firmware (a small percentage); spare blocks (another small percentage); and optionally, enhanced data protection beyond the basic error correction (space requirement varies).
 
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RetiredChief

RetiredChief

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Took a while to find, article way back in dec of last year.
Quote
For drives on the market today that don't already prioritize consistent IO, it is possible to deliver significant improvements in IO consistency through an increase in spare area. OCZ's Vector and Samsung's SSD 840 Pro both deliver much better IO consistency if you simply set aside 25% of the total NAND capacity as spare area. Consumer SSD prices are finally low enough where we're no longer forced to buy the minimum capacity for our needs. Whatever drive you end up buying, plan on using only about 75% of its capacity if you want a good balance between performance consistency and capacity
End Quote: Ref - http://www.anandtech.com/show/6489/playing-with-op

Re-reading the 25% does not not pertain to ALL SSD.
 
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