Although SSDs use the 2.5″ form factor originally designed for laptop drives, it just isn’t small enough for the upcoming tiny SFF systems – even with the thin 7.5mm height created for the Ultrabook spec.
The next step down from there is going to be the M.2 format, which you can see here at the bottom of this Crucial M500 SSD announcement. M.2 isn’t out yet though, so for now SSDs must be based on the mSATA specification.
As you can see, mSATA is slightly wider but much shorter than M.2. Its length presents a problem however – currently the largest capacity NAND die is 64 Gigabits (8GB). Since a single flash chip can hold no more than 8 die, the largest NAND flash chip is therefore 64 GB. And since the mSATA spec can only hold up to four of these chips, the most capacity a single-height mSATA drive can contain is 256 GB. The longer M.2 spec should double this, and higher capacity NAND dies are coming as well. But for now, 256GB is as big as a mSATA SSD can get.
Intel 525 Series mSATA SSD
With the release of the 525 SSD, Intel are doing something they haven’t done before as far as I can recall – they sent us the new drive in every single capacity available:
From left to right, we have the 30GB, 60GB, 120GB, 180GB, and 240GB versions of the Intel 525 SSD. Although a 90GB version was mentioned in the original announcement, there is no trace of it on the product page.
As you can guess based on the capacities, there is some over-provisioning done here. That is because the drives are using the same SandForce SF-2281 controller as recent Intel SSDs such as the 335 series and 520 series. These drives use the same 25nm Intel branded flash as the 520 series, and are over-provisioned to the same 12.6% as just about every other SandForce drive. In fact, theIntel 525 series should be practically identical to the 520 in every way other than form factor. With the exception of the 30GB model, they even carry the same 5 year warranty.
With SSDs, Capacity Brings More Performance
We know that higher capacity SSDs typically offer higher performance than lower capacity drives. You can see this immediately as soon as you look at specs sheets. The reason for this is that the more individual NAND die the controller can communicate with in parallel, the better.
This is how theIntel 525 series break down, in terms of expected performance and NAND die available to each controller:
|Total NAND (GB)||256||192||128||64||32|
|NAND Die per Chip||8||8||4||2||1|
Write performance starts to drop once there are fewer than 24 channels to the SandForce controller. Things don’t really get bad until you hit the 30GB model with its single NAND die though. This is something to look for as we get to performance testing, since sequential performance is essentially a best-case-scenario for these drives.