The m3.xlarge pairs 4 vCPU with 15 GiB of RAM, the 3.75 GiB-per-vCPU ratio that marks a general-purpose instance. In the name, "m" is the general-purpose line, "3" is the generation and "xlarge" is the size within the m3 family. It runs on Intel Xeon E5-2670 v2 (Ivy Bridge/Sandy Bridge) at 2.5 GHz, and AWS introduced it in October 2012. AWS has since shipped m4, m5, m6i and m7i; m4.xlarge is the direct replacement at this size. gp.vs1.large on Rackspace Spot lines up one-for-one: 4 vCPU and 16 GiB, $0.266/hr on AWS in US East (N. Virginia), from $0.011/hr on Rackspace Spot.
Match qualityNo local disk
m3.xlarge comes with 2 × 40 GB SSD attached to the machine. Rackspace Spot nodes use network storage only, so that disk does not come with it.
If you were using the local disk as fast scratch space — temporary files, a local cache, an index — you will need a persistent volume or object storage instead, and both are slower to read. If it was just extra space you never depended on, nothing changes.
