RevoDrive Hybrid: A Product Of Convenience?
On the surface, it's really easy to dismiss the RevoDrive Hybrid as a product that's out of touch with the needs of its target market: folks with a ton of money to spend on storage. Any enthusiast worth his tech cred should be comfortable taking an SSD, taking a hard drive, and creating a tiered storage hierarchy with performance-sensitive apps on the solid-state drive and everything else on the disk. Shoot, a 256 GB Crucial m4 and 2 TB Western Digital Caviar Green buys you two times the flash-based memory and twice as much conventional storage, saving you $50 bucks in the process. That is, perhaps, the most cost-effective approach, and we continue to advocate it as a best practice.
Frankly, OCZ's RevoDrive Hybrid isn't for that crowd. Its real target is the folks in the market for a RevoDrive 3, or even a couple of Vertex 3s slapped together in RAID. For those performance-concerned power users, this product takes the ultra-fast flash-based product and the slow magnetic storage and marries them on one PCI Express-based add-in card. On top of that, it applies caching software, which has to learn the applications and files you use most often. After three or four accesses, however, hot data finds its way onto the fast storage, where it's served up at the speed of a RevoDrive.
Needless to say, cached reads are served up very quickly. And because it employs a write-back caching strategy, writes hit the cache first, so they're fast, too. And that's where the RevoDrive Hybrid (just like a RevoDrive 3) is most compelling. If you're using the same few applications over and over, still need the capacity of a hard drive, and were already considering a solution that let you circumvent the limitations of SATA 6 Gb/s, the RevoDrive Hybrid addresses all of those needs.
Now, you could buy a PCI Express-based SSD and a hard drive separately, employing the same logic described above, and manage the capacity on each one independently. But the RevoDrive Hybrid combines both technologies in an effort to expose the benefits of each as conveniently as possible. And, it performs that task well, imposing minimal compromises.
|Market Price||Price Per GB|
|OCZ RevoDrive 3 X2 240 GB||$580||$2.42|
|OCZ RevoDrive Hybrid 1 TB||$500||$0.50|
|OCZ RevoDrive 3 120 GB + 1 TB Hard Drive||$480||$0.43|
|OCZ Vertex 3 240 GB||$460||$1.91|
There is a bit of math to do before making a commitment here, though. It'd still be cheaper to buy a 1 TB hard drive and 120 GB RevoDrive 3 separately. However, the RevoDrive Hybrid allows you to potentially enjoy a performance boost to all of your data without any physical management, with a big caveat.
Given 100 GB of available NAND, one-tenth of stored information can be cached at any one time. Once that 100 GB repository is consumed, data must be evicted from the cache at the speed of a 5400 notebook hard drive. Fortunately, workstations generally run a few programs with great frequency. As such, the RevoDrive Hybrid easily addresses project-oriented workloads like programming and video editing, where you're likely to be working with the same set of data for a long period.
One last salient point: in this case, a write-back cache is great for speed. But as we mentioned in our Z68 Express coverage, data isn't synchronized between the cache and storage device. So, if someone yanks the SSD 311 off of a Z68-based motherboard operating in write-back mode, data could very well be lost. That's not a problem here, of course. However, consider that the failure of the solid-state component of the RevoDrive Hybrid would also likely end in loss.