OCZ RevoDrive X2 240GB £470
19th Apr 2011 | 11:54
The RevoDrive doubles its capacity, but is this PCIe SSD worth it?
OCZ RevoDrive X2 review: Overview
We've had a play with OCZ's first take on the PCIe-based SSD, the OCZ RevoDrive 120GB and you could colour us fairly impressed. A little while later and the OCZ RevoDrive X2 240GB has found itself slotted into our test bench.
OCZ's first SSD-on-a-PCI-card turned out to be a neat way of getting around the bottlenecks that current (SATA 3Gbps) and future-facing (SATA 6Gbps) interfaces are finding a problem for SSDs.
Drive manufacturers are seeing that, because of data flooding the bandwidth of the I/O ports, they're not seeing the true potential of solid-state speeds.
Now it's the turn of OCZ's bigger, bolder sibling, the OCZ RevoDrive X2 240GB to come under the spotlight.
The RevoDrive X2 product line-up makes use of a daughter card to add more capacity to the original RevoDrive product range, hence the X2 part of the name.
So this RevoDrive X2 takes the PCB of the original RevoDrive we looked at and adds a daughter card laden with an extra 120GB of MLC flash memory. Added to that is another couple of SandForce controllers thrown in for good measure.
In other words, we are now looking at four 60GB OCZ Vertex 2E drives with the external cases removed and added to a couple of PCB's.
While the original RevoDrive range goes from 50GB to 480GB capacities, because of the use of the daughter card, the RevoDrive X2 doubles the capacity throughout the line-up, so the base model has a 100GB capacity while the flagship model sits just under the magical 1TB mark at 960GB.
Which, just in case you were wondering, costs an eye-watering £2,464.
OCZ RevoDrive X2 240GB: Architecture
Built on a compact 125 x 181 x 22mm PCB, the OCZ RevoDrive X2 has the same footprint as the original RevoDrive, with the daughter card sitting on very small risers above the memory chips on the base card.
In total, the X2 240GB uses 64 4GB 34mm Intel/Micron MLC (Multi-Level Cell) modules to achieve its capacity, with them being split 16 per side of the base card and 16 per side of the daughter card.
The four 64GB memory partitions are each controlled by an eight-channel SandForce SF-1222TA3 SBH controller and the data flow is controlled by an on-board SATA 3Gbps RAID controller (SiS 3124) which uses a pre-built RAID 0 (Stripe) array.
OCZ's close relationship with SandForce has enabled them to pair the controllers with the latest SF-1500 firmware, which gives better random write speeds.
While the card has an x4 PCIe 2.0 interface, with a potential 2GB/s of bandwidth (500MB/s per lane), it works only at PCIe 1.1 electronically, which gives it half the bandwith at 1GB/s.
Even this is far in excess of the 550MB/s of bandwidth that is supported by a pair of SATA cables.
This is good news, because OCZ claims maximum read/write speeds for the RevoDrive X2 of 740MB/s and 720MB/s respectively.
The one note of caution is that unfortunately the SIS RAID controller doesn't support the Windows 7 TRIM command.
The SandForce controllers do support it, but the RAID controller overrides them and blocks the command. So instead of using TRIM, the SandForce controllers have algorithms programmed into them to sort all of the rubbish data.
The worrying thing about this situation is that the OCZ RevoDrive X2 has the potential to really suffer from a downward spiral of performance coinciding with its long-term use.
OCZ RevoDrive X2 240GB: Benchmarks
To test the RevoDrive x2 in as close to a real life scenario as possible it was installed as a boot drive and a full operating system was installed. We tested in this state and then filled it up with data and then deleted it, running through this cycle a few times before testing the drive again to see if there was much difference in the results after subjecting the drive to this usage cycle.
There wasn't a great deal of difference between the two sets of results, although there still might be through longer-term usage.
Sequential read/write performance
Burst speed performance
Real-world usage performance
OCZ RevoDrive X2 240GB: Verdict
You might be wondering why OCZ is investing in an alternative to the SATA I/O interface just when everyone else is climbing on the SATA 6Gbps bandwagon.
Well, one answer is that the specifications for the next generation of SandForce controllers have sequential read/writes requirements of up to 500MB/s.
So you'll have to forget about SATA 3Gbps, (375MB/s) and it's also nearly enough to flood the SATA 6Gbps interface.
Secondly just take a look at OCZ's claimed maximum sequential read and write performance of the RevoDrive X2 240GB.
At 740MB/s and 720MB/s respectively, that's incredible speed, and as the results of the ATTO sequential read/write tests confirm (733MB/s and 735MB/s) these are not pie-in-the-sky figures.
The standard SATA interface, as it currently stands, is more of a hindrance than a help. This is why it makes more sense to use a PCIe slot, even one running at PCIe 1.1 speed.
Like its sibling, the original RevoDrive, the X2's forte is moving large or highly compressed files around. It doesn't quite impress so much when it comes to shuffling small bitty files about, as confirmed by the test results using our 1GB zip file test.
The test file is made up of loads of little files and the RevoDrive X2 struggled to put a lot of daylight between itself, the original RevoDrive and a RAID 0 (striped) array built from two standard 128GB SSDs.
In an ideal world, these should have been four of OCZ Vertex 2E's for more of an apples versus apples test, but a pair of Kingston 100V+ drives still gives a good indication of relative performance. Having said that, it did do the job three seconds faster than the RevoDrive and some eight seconds faster than the RAID array.
The price seems unreasonably high at first, and maybe even third, glance, but if you wanted to go down a similar path building your own RAID array using four 60GB Vertex 2E drives, you're not going to get much change out of four hundred quid.
Plus, there's the fact they will take up four of your SATA ports.
Or you can go down another path and buy a high quality four-port RAID card, adding even more to the price. So when looked at against those pricey options the OCZ RevoDrive X2 begins to look the better option, it's certainly the neater one.
Once formatted, Windows reports the capacity of the drive to be 223GB thanks to a chunk of memory needed for over-provisioning duties.
Over-provisioning is one method of maintaining an SSD drive's performance by dedicating a chunk of memory for use as empty blocks for jobs such as address mapping, writing and the removal of dead blocks without reducing the drives capacity or performance and increasing the life of the drive.
As with the original OCZ RevoDrive, the OCZ RevoDrive X2 240GB is an interesting way of getting around the current limitations of the SATA interface by using the PCIe bus, and we can only imagine what the performance would be like if drives like this could access the full bandwidth of the PCIe 2.0 specification.
As it is it's a blisteringly fast, but by no means a perfectly performing drive.
OK, it's the same minor quibble as with the RevoDrive, but why aren't the drivers you need to install the RevoDrive X2 during a Windows installation included in the box?
It's all very well them being on OCZ's website but if you're installing the drive and don't have internet access, then you're screwed, quite frankly.
If you work with very large or highly compressed files and have the budget, then adding the RevoDrive X2 to your system makes perfect sense. For the rest of us, well, we can dream...