One of the most common emails we get is in regards to overprovisioning; or as some call it the ‘spare area’. This is NAND inaccessible to the user that’s set aside by the manufacturer to assist with drive longevity by having “fresh” NAND available to the controller when blocks begin to wear out. It also assists with drive maintenance duties by having an ‘always available’ swap space present for this important activity. By now, most people are well aware of this concept so we don’t always reiterate the point but only make reference to it for the sake of brevity. However, there’s much confusion around the actual amount of spare area mainly because of the whole GB (1GB =
1,000,000,000 bytes) vs Gib (1 GiB = 1,073,741,824 bytes) nomenclature.
In the case of this Micron P400e 200GB drive (note the 200,047,325,184 bytes number in the image below), there’s a total of 256GB of flash on board which equates to 238GiB. Windows reports in terms of GiB although it confusingly labels the measure as GB. As we see below, the drive has 186GiB available to the user so simple math tells us that Micron set aside 52GB or nearly 22%. Micron actually breaks it down on their blog for a little light reading.
As we referenced in the introduction, at first blush, the performance numbers of 350MB/s reads and 140MB/s reads don’t look all that enthralling but we found that in several of the benchmarks, the performance was much better than that. At any rate, most business applications don’t require the raw speed that enthusiasts crave so burying the needle on the speedometer isn’t necessary which also can mitigate the power draw. It is their entry level enterprise SSD so you can’t expect mind-blowing performance. Also on the plus side is the fact that the Marvell controller handles compressible and incompressible with equal adeptness.
On the downside, the 4k writes were the lowest we’ve seen out of all the drives in our comparisons for all benchmarks. This didn’t manifest itself in a noticeable way during normal use but some applications may suffer as a result. The NAND employed by Micron is consumer grade which generally has less endurance than that of its enterprise counterpart although I’m sure since it’s Micron’s own manufacture, they weren’t picking bottom of the barrel parts. Micron rates the 200GB drive as having 175TB of total lifetime bytes written and 1.2 million device hours which is all assisted by the aforementioned generous overprovisioning. Lastly, unlike that of the SandForce controllers, the Marvell controller offers no native encryption that we’re aware of which is something businesses are keen on.
At the time of this writing, we don’t have the actual pricing for the drives but we’ll make an update as soon as Micron gets back with us. In the interim, we’ll parrot the information present on Micron’s marketing materials and say that in reference to enterprise application, the p400e drives are optimized for low total cost of ownership (TCO) and “outstanding IOPs-per-watt and dollars-per-IOP”. We know the Marvell controller is rather cost-effective when compared to some of the other popular controllers and offers solid performance although a bit slower in some aspects – specifically 4k writes. This may be less of a concern for more users than that of reliability which Micron has addressed with the enterprise data-path protection in the firmware.
Update at 3pm on 03/26/2012: Micron got back to us this afternoon with the prices of the P400e series of SSDs:
Pricing for the P400e can vary based on multiple factors, but our distribution pricing for monthly quantities of 500 to 1000 drives is currently $100, $175, $330 and $655 for the 50GB, 100GB, 200GB and 400GB drive, respectively. – Micron PR
Legit Bottom Line: Intended for business users, the Micron P400e offers solid performance coming and data reliability from its custom firmware driven Marvell 9174 controller, although the lack of encryption and weak 4k writes are definitely soft spots which may not be too much of an issue for some – especially if the price is right.