The Difference Between Professional and Mainstream SSDs
SSDs are now becoming more common in consumer computers and are almost mainstream when it comes to professional computers or high-end gaming rigs. We often see them used as OS drives with a large traditional mechanical drives doing duty as media and document storage.
On paper, SSD technology has spinning magnetic drive technology beaten in every way except price per GB. They are much faster, much less prone to failure and not sensitive to physical forces to the same degree as mechanical drive, but not all SSDs are created equal.
First, ALL SSDs degrade when writing data. After a certain number of writes to a given memory element that element will fail. Early SSDs could be destroyed using software torture tests in a distressingly short amount of time. These days the endurance of consumer grade SSDs has been improved immensely through better manufacturing processes, better firmware and better operating system support.
But there’s still a big difference between the write endurance of mainstream drives and professional- or enterprise- class drives. So if you are intending to use a drive for jobs that require lots of data writing operations you might want to think twice about which SSD you fork out for.
Samsung EVO (left) uses SLC memory / 3 Year Warranty - Samsung Pro (right) uses MLC memory / 10 Year Warranty
There are three types of flash memory used in SSD drives: SLC, MLC and TLC.
SLC Single Level Cell flash memory is the simplest, fastest and most robust flash memory you can get. It only stores one bit per cell of memory and is structurally very simple, hence the reliability. The firmware also doesn’t need to do anything complex to make SLC work compared to other types of flash, so there’s little processing overhead to speak of. SLC is however prohibitively expensive and because of the lower data density doesn’t come in huge sizes. In terms of write endurance though, this technology is virtually bulletproof. Generally SLC will tolerate 10x the writes of MLC, which we talk about next. MLC Multi Level Cell flash memory is the kind you are most likely to find in an SSD you’d actually buy. These units have two bits of memory per cell and therefore are cheaper and have larger sizes, but do not match up in terms of speed and reliability compared to SLC.
To give you a more concrete idea, the rated write endurance on the Mushkin Reactor 1TB SSD is 144TB. That’s on 16 nm MLC technology. That translates to about 130 GB of writes per day for three years (the warranty period) before drive failure. That’s perfectly OK for a desktop PC or even for professionals who don’t do work that writes a lot to the drive, but would you put that in a server? What about writing large working files such as video editing projects or other storage heavy creative outputs?
To help mitigate this issue there’s a special version of MLC known as eMLC, the “e” being short for “enterprise”. eMLC is MLC that has been enhanced to take more write cycles before breaking down. So, depending on your needs, eMLC drives might hit the sweet spot between price and performance when looking at enterprise applications.
How much of a difference does eMLC make to endurance? The Samsung 850 EVO 500GB unit, which is a great consumer drive, has a write endurance of 150 TB. The Samsung SM825 400GB eMLC drive has a write endurance of 7000TB. That’s a huge difference, to burn out the drive within its five year warranty period you’d have to write 3.8 TB of data per day, every day to the device. Clearly eMLC is something to watch out for if write endurance is going to be an issue to you.
TLC Triple Level Cell flash memory steps up the data density to three bits per cell, which as you’d expect lowers everything else from speed to write endurance, but at a cheaper price and way faster than a traditional HDD.
This low-end flash is best used for extremely light client workloads or drives that will mostly be read from, such as drives holding video for streaming or a file server. Remember that, write endurance aside, SSDs have a MTBF (mean time before failure) measured in decades or centuries, so they are much more reliable than magnetic drives. TLC has its place, but it isn’t in the professional or write heavy enterprise realm.
Measure Twice, Cut Once
If you are planning on getting Titan US to build you a server or workstation, discuss your plans for the machine with us so we can make sure that you fit the right kind of SSD to your computer. Apart from write endurance there are factors such as speed, capacity and price to take into consideration. Picking the right SSD can be a challenge, so don’t hesitate to speak to us. It could save you a lot of money or a big headache.