OCZ Deneva 2 R 200 GB eMLC Review
Published by Marc Büchel on 21.11.13 (20654 reads)
Since quite a few years OCZ is covering ground in the enterprise SSD market. In this regard the entry-level market gets supplied with their Deneva 2 series, where there are several different models. The main differences can be found with the different types of flash memory. Today we're having a closer look at the 200 Gigabyte Deneva R eMLC drive, which features high endurance. Should you run, lets say a storage appliance where performance is critical and which has to cope with huge amounts of host writes, then it won't hurt to have a closer look at this drive. The Deneva 2 becomes especially interesting if you have to realize a cost effective solution.
The OCZ Deneva 2 series of SSD's offers quite a few different models. In this case we're having a closer look at the Deneva 2 R eMLC Series drive with 200 Gigabyte. On the following paragraphs and pages we will give you a heads-up on specs, expected endurance and Performance.
The core of this SSD is the LSI SandForce SF-2582 controller and it's available with either 100 Gigabyte, 200 Gigabyte or 400 Gigabyte usable disk space. In case of the 200 Gigabyte drive we're reviewing here OCZ is using 56 Gigabyte for overprovisioning purposes, which is roughly 22 percent of the entire capacity. This might sound like a lot but considering this is an enterprise drive it makes sense. Lets make quick example what overprovisioning is about. I'm quite sure you all know the little game, where you have 15 stones numbered from one to 15 and the 16th stone doesn't exist. These sixteen stones are arranged in a four by four matrix and the goal is usually to arrange the numbers in a consecutive order. Since you have only one stone you can move you will have to move quite a few other stones too to get things the right way. Imagine now you had four or even more empty slots, this would make the problem much easier and quicker to solve. Translated to an SSD this means that overprovisioning helps keeping performance high and write amplification factor low and especially the latter has quite an impact on endurance.
Another key feature of this particular drive comes with the NAND flash that is being used. In this case it's not standard consumer-grade MLC NAND this drive ships with. OCZ equips the Deneva 2 R with eMLC memory which offers much higher P/E cycle count. The "e" in front of MLC stands for enterprise, which should give a hit too, that this drive is not only about performance but also about endurance. Comparing P/E cycle counts of MLC and eMLC shows, that MLC features between 3'000 and 5'000 whereas eMLC offers 20'000 to 30'000 P/E cycles. Worst case it's four times and best case it's ten times as much. In other words this drive has been made to cope with write intense workloads in server environments. OCZ doesn't provide the P/E cycle count of the NAND flash cells directly, but they do provide an amount of data written when it comes to endurance. In case of the 100 Gigabyte drive this is 19 PBW, with the 200 Gigabyte it's already 38 PBW and with the 400 Gigabyte model you get 76 PBW. The fact that the value is going up by a factor of two is a result of the amount of memory being doubled. In this case there are twice as many NAND Flash memory cells available which also means there are twice as many P/E cycles available.