Today, Micron has announced a new member of its enterprise SSD family, the M500DC. Typically, Micron likes to focus on performance and reliability with their enterprise drives, with cost being a secondary factor. With the M500DC, they have made price a priority.
About this time last year, we were reviewing the Crucial M500 960GB. This was the first drive to really put 1 TB of flash storage at a price where consumers could realistically own one. In the past year, Micron released the enterprise-focused M500 under their brand. They are now back with the M500DC that shares its roots with both of those drives.
By using the base architecture of the M500, Micron is able to add enterprise features to a drive that is consistently selling for less than $0.50/GB. Considering the lowest cost enterprise SSDs are close to $1/GB, this gives Micron a lot of room to be price competitive. Micron does not publish pricing for their enterprise SSDs, instead they point you to distributors to get pricing at volume. But, in our conversations, they heavily implied that they would very competitive.
Beyond pricing, the M500DC shares a lot of features that we are use to seeing in Micron’s higher priced enterprise SSDs. The M500DC incorporates all of Micron’s XPERT features set (RAIN, ARM/OR, ReCal and eDPP). All of these features drastically increase reliability, which is why they are able to push 20nm MLC NAND into the enterprise space.
Micron is marketing this drive for cloud and web 2.0 storage applications. They are focusing on 24/7 operating, write optimized workloads, and high reliability and availability. This is different from the read-optimized SSDs that we have reviewed over the past year.
When looking at specifications for enterprise SSDs, you have to be really careful not to get caught up on individual numbers on the data sheet. In order to evaluate an SSD effectively, you have to look at the big picture of how each specification helps the drive to perform its given task.
The M500DC, as an SSD designed for write optimized workloads, has some great write characteristics. At 35K write IOPS, the M500DC is at the top of its class. With write endurance of 1.9PB at the highest capacities, the M500DC offers a good middle ground between read-optimized SSDs and eMLC SSDs, such as the Micron P400m.
Read performance is slightly lower than most enterprise SSDs, at 65K IOPS. Sequential operations, both read and write, are also lower. The lower read rates could be a cause for concern, but until we run the actual tests, we will reserve judgement. Power consumption is on par with other SSDs at those capacities.
One interesting thing to note is that the M500DC is offered in the 1.8″ form-factor at all capacities. This form-factor gained some traction in the micro/blade server space, but is still an oddity for most SSD manufacturers.
The first thing you notice once you remove the outer case is the small number of NAND packages on the M500DC. Each NAND is 128GB, which consists of 8 die with a density of 16GB. There are a total of 8 NAND packages on the 800GB model for a total of 1024GB.
For many SSD manufacturers, you would, based on the 800GB model, have a 400GB model with 512GB of total NAND. Instead, Micron has a 480GB model with 768GB of total NAND. This pushes the amount of over-provisioning from 28% to 60%. The reduction of that ratio is what accounts for the 800GB model having fewer write IOPS and identical write endurance as the 480GB model.
The cache is Micron 1GB DDR3 SDRAM (2 x MT41K256M16HA-125), one on each side of the printed circuit board (PCB).
Micron also chose to stick with the same controller as the M500 by going with the Marvel SS9187.
Finally, there is a bank of capacitors that is used for power loss protection. In the event of sudden power loss, these capacitors will keep the drive going long enough to commit all data from the write cache to NAND.