Fabric Expansion Calculator
Check whether new leaves fit the existing spines, and count the spine ports, cables and bandwidth they add.
About Fabric Expansion Calculator
Each new leaf consumes one port on every spine for each parallel uplink, so spine port count — not rack space — is what caps a two-tier fabric. When it runs out the options are a super-spine tier, fewer uplinks per leaf, or faster uplinks. Discovering the spines are full during a build weekend is the classic data-centre stall; this is the arithmetic that should be done at design review.
Formula
Fabric Expansion
ports used per spine = total leaves × uplinks per spine; added bandwidth = new leaves × spines × uplinks per spine × uplink speed.
- uplinks per spine
- Parallel links between one leaf and one spine
- maximum leaves
- Spine fabric ports divided by uplinks per spine
Worked example
With the default values below, Fabric Expansion Calculator returns Fabric Bandwidth Added of 6,400. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Leaves todayaccepts 0–512 switches
- 16 switches
- Leaves being addedaccepts 1–512 switches
- 8 switches
- Spine switchesaccepts 1–64 switches
- 4 switches
- Uplinks from each leaf to each spineaccepts 1–16 links
- 2 links
- Fabric ports available per spineaccepts 1–512 ports
- 64 ports
- Uplink speedaccepts 1–800 Gbps
- 100 Gbps
Results
- Fabric Bandwidth Added
- 6,400 Gbps
- Leaves after Expansion
- 24
- Spare Ports Left on Each Spine
- 16
- Maximum Leaves These Spines Support
- 32
- New Fabric Cables Required
- 64
- Fits Without Adding Spines
- Yes
Step by step
- 1Values used
- 2Fabric Expansion
- 3Fabric Bandwidth Added= 6,400 Gbps
- 4Leaves after Expansion= 24
- 5Spare Ports Left on Each Spine= 16
- 6Maximum Leaves These Spines Support= 32
- 7New Fabric Cables Required= 64
- 8Fits Without Adding Spines= Yes
Assumptions and limits
- The result is derived only from the 6 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Fabric Expansion calculated?
ports used per spine = total leaves × uplinks per spine; added bandwidth = new leaves × spines × uplinks per spine × uplink speed. Each new leaf consumes one port on every spine for each parallel uplink, so spine port count — not rack space — is what caps a two-tier fabric. When it runs out the options are a super-spine tier, fewer uplinks per leaf, or faster uplinks.
Why does Fabric Expansion matter?
Discovering the spines are full during a build weekend is the classic data-centre stall; this is the arithmetic that should be done at design review.
What values do I need to enter?
This calculator takes 6 inputs: Leaves today, Leaves being added, Spine switches, Uplinks from each leaf to each spine, Fabric ports available per spine, Uplink speed. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.