Single 512 SSD vs 2x256 (RAID) SSD

Hi folks,

For my new system, I find myself going back and forth between raided drives and a single, larger drive. Originally I had thought to raid, as I thought that would get me a performance benefit - but doing some research, it seems that SSD's are fast enough in general that the benefit from raiding 2 vs. getting one large one isn't really all that much.

My old plan was the dual 256's, now I'm thinking a single 512 - and maybe either adding a second 512 down the line, or dropping a 1TB data HDD in the second slot of my laptop. (originally, the RAID was there for performance, but if there's not all that much performance advantage it seems much better to get more flexibility in the future with an open bay slot)

So, looking for the learned opinions here. All other things being equal (and they nearly are; there's only like $50 diff between the configs), would you rather do the single 512 or the dual 256's, and why?

(If it matters, the drives I'm considering are Samsung 840 Pros)

 

The main benefit of RAID is to increase bandwidth to allow faster sequential transfer speeds, plus, the additional drive also improves random performance at higher queue depths. However, you will not have an improvement in snappiness because most of those 4k Random operations are done at a queue depth of 1 (i.e. the operation cannot be spread among 2 drives) hence you are bound by the latency of the individual flash chips.
You musn't forget that your sequential transfers will most likely be bottlenecked by the slowest drive, this means that you won't notice the massively improved sequential speeds unless you are transferring to another SSD RAID array.
The other benefit of RAID SSDs (performance at high queue depths) is also quite minimal in most usage scenarios since most of your operations on your Laptop/Desktop are not IO bound, unless you are running a database with dozens of users.

The disadvantages of RAID SSDs are considerable. You have much lower reliability since there are double the number of flash cells (I think the 512 model uses high density cells) and 2 controllers that can theoretically fail. Additionally, the performance consistency suffers as each individual SSD has less flash cells for Spare Area and possibly endurance issues as each SSD has half as much flash cells for wear levelling.
The most important disadvantage of RAID SSDs is the loss of TRIM. Unless you can confirm that your machine has the latest OROM, you will get a gradual performance degradation with the RAID array.

 

512GB SSD.

Btw Samsung PROs have problem with RAID or at least with earlier firmware for sure.