Are SSDs really 10x cheaper than RAM?


I am often asked about the cost of SSDs (Flash) compared to RAM.

“Flash, it’s so expensive,” people say.

Is it? The answer quickly becomes complex.

The industry has changed rapidly over the last few years, with rapidly changing prices. There have been expensive enterprise devices. There are slower consumer-oriented Flash drives with lower performance. RAM is also complex – faster, slower, higher and lower power draw & densities. Power has different prices in different regions of the world. Density is a factor. It’s hard to know where to start, let alone make a fair comparison.

Let’s simplify. Let’s look at Amazon.

Amazon has two main RAM offerings. In US Virginia, the cost of a “memory optimized” (ie, lower CPU) instance (r3.4xlarge) is (as of Jan 15, 2015) $1.40/hour for for 122 GB (and includes 320G of ephemerial SSD). A “compute optimized” instance would be a c3.4xlarge giving 30GB for $0.84/hour (with 320GB SSD).

Different R3 instance sizes have the same price per byte, as do c3 instances.


r3 – 0.011 $ / GB * hour

c3 – 0.028 $ / GB * hour

Flash optimized instances are the i2 instance class. An i2.xlarge is 800GB of SSD for $ 0.853 / hour (with 30.5 GB of RAM). Like the R3 and C3 instance types, larger instances have the same price per byte.

Flash –

i3 – 0.00107 $ / GB * hour

Look at that.

Almost exactly 10x cheaper.

Power included, CPU included, data center floor space included, management cost included, SSD wear included.

Can you achieve this with other cloud providers, or in your own data centers?

You can.

Just remember to use a memory optimized database like Aerospike to get the highest level of performance, regardless of whether you’re using RAM or Flash.