Instances›AWS EC2›c5›c5.18xlarge
Compute
vCPUs72
Memory144 GiB
Mem / vCPU2.00 GiB
ProcessorXeon Platinum 8124M
Clock speed3.4 GHz
Architecturex86_64
Storage
TypeEBS only
Bandwidth19,000 Mbps
Throughput2375 MB/s
IOPS80,000
Networking
Performance25 Gigabit
Max ENIs15
IPv6Yes
GPUNone
Family sizes
c5.large2 vCPU · 4 GiB
c5.xlarge4 vCPU · 8 GiB
c5.2xlarge8 vCPU · 16 GiB
c5.4xlarge16 vCPU · 32 GiB
c5.9xlarge36 vCPU · 72 GiB
c5.12xlarge48 vCPU · 96 GiB
c5.18xlarge72 vCPU · 144 GiB
c5.24xlarge96 vCPU · 192 GiB
c5.metal96 vCPU · 192 GiB
c5.18xlarge

c5.18xlarge is AWS's compute-optimized EC2 size at 72 vCPU and 144 GiB. In the name, "c" stands for compute, "5" is the generation and "18xlarge" is the size within the c5 family. It runs on Intel Xeon Platinum 8124M at 3.4 GHz, and AWS introduced it in November 2017. AWS has since shipped c6i, c7i, c8i and c9g. The closest Spot shape is ch.vs1.2xlarge at 16 vCPU, so this instance maps to 5 of them — 80 vCPU and 160 GiB across the fleet, about 93% below the US East (N. Virginia) on-demand rate. Spot delivers compute as managed Kubernetes, so a node pool of that size is the native shape of the answer rather than a workaround — provided the workload scales horizontally.

Match qualityScale-out match

c5.18xlarge gives you 72 vCPU and 144 GiB in a single machine. The largest comparable Spot node, ch.vs1.2xlarge, is 16 vCPU and 32 GiB, so the equivalent here is 5 nodes rather than one.

Spot runs as managed Kubernetes, so a 5-node pool is the normal way to run things rather than a workaround. If your workload already sits behind a load balancer, a queue or a scheduler, it spreads across them without changes. If it needs all 72 cores and 144 GiB in one process, it does not.

Pricing by region
1 hr
RegionAWS on-demandAWS Spot1-yr Reserved3-yr ReservedRackspace SpotYou save
US East, N. Virginia$3.060$0.890$1.928$1.282$0.205
$2.855 savings
US Central, Chicagono AWS region$0.055
US Central, Dallasno AWS region$0.555
Hong Kong$3.888$2.449$1.680$0.205
$3.683 savings
Sydney, Australia$3.996$1.377$2.517$1.726$0.205
$3.791 savings
London, UK$3.636$0.421$2.291$1.571$0.655
$2.981 savings
US West, San Jose$3.816$1.130$2.404$1.649$0.009
$3.807 savings
US Central, Dallas 2no AWS region$0.549
US East, N. Virginia 2$3.060$0.890$1.928$1.282$0.729
$2.331 savings
When to use it
Good for
  • ●Batch processing and CI/CD runners
  • ●Video encoding and transcoding
  • ●High-traffic web and API serving
  • ●Workloads that fit inside 144 GiB of RAM
  • ●Parallel work that can occupy 72 vCPU
  • ●Network-heavy services — AWS rates this size at 25 Gigabit
  • ●Anything that shards cleanly across 5 nodes, which is how it maps onto Rackspace Spot
Avoid if
  • ●The working set needs more than 144 GiB of RAM
  • ●More than 2.00 GiB of RAM per vCPU is needed — that ratio is fixed for the whole family
  • ●The work is single-threaded. Most of these 72 vCPU would sit idle.
  • ●Local NVMe or instance-store disk is a hard requirement
  • ●GPU or FPGA acceleration is needed
  • ●Memory-hungry applications. A memory-optimized family gives more RAM per dollar.
c5.18xlarge runs $2,234/mo on AWS on-demand. The 5-node equivalent on Rackspace Spot: $150/mo.
  • Spot sells spare capacity at market prices. It is the cheapest compute on the internet.
  • Prices are set by supply and demand. You pay what the market decides.
  • Compute is delivered as fully managed Kubernetes. All infrastructure is taken care of.
  • Egress costs $0.01/GB after the free allowance. AWS charges $0.09/GB.
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