PCIE vs SATA Express SSD

The common performance metric for ssd's of all types are really not much relevant to what a normal desktop user does.

Do not be much swayed by vendor synthetic SSD benchmarks.
They are done with apps that push the SSD to it's maximum using queue lengths of 30 or so.
Most desktop users will do one or two things at a time, so they will see queue lengths of one or two.
What really counts is the response times, particularly for small random I/O. That is what the os does mostly.
For that, the response times of current SSD's are remarkably similar. And quick. They will be 50X faster than a hard drive.
In sequential operations, they will be 2x faster than a hard drive, perhaps 3x if you have a sata3 interface.
The theoretical advantage of pcie or sata express is attractive, but may be an illusion.

Larger SSD's are preferable. They have more nand chips that can be accessed in parallel. Sort of an internal raid-0 if you will.
Also, a SSD will slow down as it approaches full. That is because it will have a harder time finding free nand blocks to do an update without a read/write operation.

I'm using 2/4 way raid0 made out of 520/530 Intel SSDs, if You want rough power, go for it. Just watch out for mobo. You need 4 SATA 3.0 ports with single controller on board NOT marvell, it has to be intel. Otherwise You'll get massive performance degeneration.

I think there is a lot of misunderstanding about SATA Express. In the new SATA 3.2 standard that was officially adopted last year the new SATA Express interface/connector was actually designed to be very flexible. It can support standard SATA 3 6Gb/s ssd's and PCIe ssd's. You can connect a standard SATA 3 6Gb/s ssd with a standard SATA cable and it will work. That is as far as it goes for now. It does not look like we will be seeing much in the way of actual SATA Express ssd's. There has been speculation and unsubstantiated rumors that one or two SATA Express ssd's might be available before the end of the year but I have not been able to confirm it.

USAFRet posted a link to a really great article over at AnandTech which explains SATA Express. Everyone should read it for a better understanding of the new header/connector. Currently there are no actual SATA Express ssd's. Temporarily just consider the new SATA Express header/connector as another SATA connector for SATA 3 6Gb/s ssd's.

Although motherboard manufacturers have included SATA Express headers/connectors on new Z97 and X99 motherboards, that is not their actual preference. Both motherboard and ssd manufacturers have a preference for the new M.2 NGFF ssd's and for a very good reason.

For the past several years sales of desktp pc's have been declining while sales of mobile pc's have been increasing Last year mobile pc's outsold desktop pc's. The same thing is happening this year. The new M.2 ssd's were specifically designed for mobile computing. The M.2 ssd's are also suitable for desktop pc.'s. It is a situation where it was more economical to go with M.2 ssd's instead of SATA Express ssd's.

There is quite a bit of flexability with the new M.2 headers/connectors. There are several variations:

1. M.2 PCIe 3.0 x 4
2. M.2 PCIe 2.0 x4
3. M.2 PCIe 2.0 x2
4. SATA 3 6Gb/s
5. Various combinations of PCIe and SATA 3 6gB/S

The vast majority of M.2 headers/connectors on motherboards are M.2 PCIe 2.0 x2. Motherboard companies have also managed to cause quite a bit of confusion. Most of the specifications mention M.2 but do not identify which variation. ASRock is the one exception. The company did a good job of identifying the M.2 variations in their specifications.

There are other variations of PCIe ssd's. They can be mounted on a pcb board which is inserted into a PCIe slot on a motherboard. The same ssd can also be enclosed in a shroud. The ones I saw looked like half height, half length graphic cards. They can also be mounted inside a standard 2.5 inch ssd enclosure mounted in a drive bay and connected to the motherboard with a cable.

Currently the world's fastest consumer ssd is the Samsung XP941 M.2 PCIe 2.0 x4 ssd. Samsung has been mass producing and distributing the XP941 for almost 18 months now. We haven't heard very much about it because it is OEM only. Samsung has lucrative contracts to supply the ssd to computer companies such as Dell, Lenovo, Apple, Acers and others. Samsung never released a retail version for consumers. It wasn't until earlier this year that a few select vendors started selling the XP941 as a replacement ssd.

Samsung is working on their new SM951 M.2 PCIe 3.0 x4 ssd. In addition to the upgrade to PCIe 3.0 x4, the ssd will have some other new features. Among the new features is NVM Express (NVMe) which will be replacing the old ACHI mode. If all goes well mass productin and distribution to OEM partners will start in about 6 months. It is not known whether a retail version will be available for consumers. Two days ago ASRock released their brand new X99 Extreme11 motherboard. The board is equipped with two M.2 PCIe 3.0 x4 headers/connectors. The bad news is the board is equipped with so many extra features it costs $649.99 USD.

I maintain the ssd database listed in a sticky at the very top of this forum section. Here is the link:

http://www.johnnylucky.org/data-storage/ssd-database.html

The database includes seperate PCIe and M.2 categories for each brand plus links to published technical reviews.

Btw. if You're "powerhungry" and raid0 ain't enough [most of the time You hit 1-1,1 GB/s, have You considered RAM drive? Just ried it out today, it's craz thing.

Since I'm on my way to bed, I'll answer number 4:

HDD:
+ long term storage
+ high latency
+ higher durability [most of the times]
+ can take more punishment what about read/write operations [iOPs also]
- takes more time to load Your os/software
- tend to heat up
- superslow compared to SSDs
- power consumption
- needs defragmentation

SSD:
+ low latency [literally hundred times lower than with HDDs]
+ ultra speed
+ doesn't dissipate much heat into environment
+ ultimate iOPS
+ excellent startup times of programs/os/everything
+ eats almost no juice at all [most of the clients noteboosk went up 30-90 minutes after replacing their old HDD with SSD]
- suffers from many rewrites
- needs trim[ming]
- some SSDs suffer from many errors, low-life of NAND cells, etc.

4. Cost vs space.

5. As an SSD get close to full, it takes longer for the firmware to find spaces to write to. Plus, those few free spaces get written to much more, and those cells will die sooner.
Leave 10-15% free, and the drive will have enough space free to perform its wear leveling.

Traditional defrag as with HDD's is generally not recommended for an SSD. Let the internal firmware, and TRIM do that.

Your decision is simple:
1. Buy a ssd for the "C: drive.
240gb if you can, 120gb if you must.
Samsung or intel are best, buy the cheapest.

2. For bulk storage and overflow use a 7200rpm hard drive.

Nothing at all wrong with a single 500gb ssd. The prices are coming down.
On a 1tb pcie ssd at a similar price, I am a bit skeptical.
Exactly what pcie device did you find?

Found where? Have a link for this?

That is a hybrid drive, not a true ssd. It is a device, I think, with a ssd front end and a hard drive at the back.
Performance will be gated by how much nand is attached to the front end. I might guess not much.
The specs are silent on this, but the assd tests are telling.
The max sequential speed comes from the pcie interface, but the average sequential speed is 1/2 of a conventional sata ssd.
Similarly, the average random I/O is perhaps 1/2 the capability of a standard sata ssd.

Not a good deal in my opinion.