Why the vSAN capacity true up clause costs more than the headline rate.

Sitting inside every recent vSAN contract is a capacity true up clause that the seller frames as administrative. It is not administrative. It is the single most expensive line in a vSAN renewal motion, and almost every buyer signs it without reading what it actually does. The clause obligates the buyer to a price reconciliation at the end of each measurement period against the seller's recorded capacity, at a rate the seller controls, with a remedy mechanism that protects the seller and not the buyer. Each of those three components carries a cost the headline rate does not surface.

The clause is presented as protection against overcommit. The seller frames it as a way for the buyer to start small and add capacity as needed without renegotiating. The framing is accurate as far as it goes. What the framing leaves out is the rate the additions are priced at, the timing the seller controls, and the cap the clause does not include. The buyer who reads only the headline rate and signs the clause as written is signing a price escalator that compounds against capacity drift across the contract term.

Component one: the true up rate is not the contract rate

The first cost sits in the true up rate itself. The buyer contracts a rate against the initial capacity. The clause specifies that any capacity above the initial amount is billed at a true up rate that is defined by reference to the seller's then current list, not by reference to the buyer's contracted rate. Two years into the term, the seller's then current list is roughly 18 to 24 percent above the contract rate by the seller's own published escalations. The buyer who consumed an additional 200 terabytes in year two pays for that 200 terabytes at a rate 22 percent above what the original 1,000 terabytes are priced at.

The clause language is rarely explicit about this. The reference is to a published rate sheet that is not attached to the contract and that the buyer is not normally provided. The seller's interpretation of the clause is the operative interpretation until the buyer challenges it, and by the time the buyer notices the rate at a true up reconciliation, the capacity is already deployed and the buyer is committed.

Component two: the measurement period favours the seller

The second cost sits in the timing. The clause specifies a measurement period, usually annual, with a true up reconciliation at the end of each period. The peak capacity used during any moment in the period is the basis for the reconciliation, not the average and not the year end position. A buyer who provisions a temporary capacity peak for a migration or a backup window pays for the peak as if it were sustained, because the clause does not distinguish.

A representative example from a recent reconciliation we reviewed had the buyer running at an average 1,140 terabytes across the year, with a 14 day peak at 1,420 terabytes during a planned migration. The clause billed the buyer for the peak, treating it as the year's effective capacity. The differential between the average and the peak, at the true up rate, produced a reconciliation invoice 31 percent above what the average would have produced. The buyer paid the invoice. The clause did not give the buyer grounds to challenge it.

"The clause says the buyer can add capacity without renegotiating. What it does not say is that the addition is priced at the seller's then current list, measured against peaks, and remedied through a payment the buyer cannot defer."Renewals Lead, The Desk

Component three: the remedy mechanism is one directional

The third cost sits in the remedy. The clause specifies what happens when the buyer's capacity exceeds the contracted amount. It does not specify what happens when the buyer's capacity falls below the contracted amount. The buyer pays additional for overconsumption. The buyer does not receive credit for underconsumption. The seller's published position is that the contracted capacity is a commit floor, not a meter, and the buyer signed for that floor regardless of subsequent consumption.

The result is asymmetric. A buyer who overshoots the floor pays at the seller's higher rate. A buyer who undershoots the floor pays for capacity not consumed at the contracted rate. There is no scenario in the clause as drafted where the buyer's bill goes down. The clause is structured as a one way ratchet. The headline rate is the floor of what the buyer pays, never the ceiling.

What the buyer side rewrite looks like

The Desk rewrites this clause as a standard part of any vSAN engagement. The rewrite has three components. First, the true up rate is locked to the contract rate plus an explicit and bounded escalator, with the escalator defined in the contract itself and not by reference to a published list. The escalator is normally written at the lower of consumer price index or 4 percent annually. Second, the measurement basis is changed from peak to a defined window average, with planned exceptions for migration and recovery activity disclosed in advance. Third, the remedy is made bidirectional, with a true down provision that credits the buyer for sustained underconsumption against the contracted floor at a defined rate.

Each of the three rewrites produces yield independently. Together they convert the clause from a one way ratchet into a reconciliation that operates symmetrically. The seller resists each component. The seller's resistance is procedural at first, then narrows to specific terms, then accepts a version of each. The negotiation typically takes two cycles. The clause language is not unusual once the conversation happens.

What we have seen on live deals

A Fortune 200 healthcare network contracted a vSAN deployment in 2024 with an unmodified capacity true up clause. The buyer ran a planned data centre migration in 2025 that pushed peak capacity 24 percent above the contracted floor for a window of 19 days. The reconciliation invoice priced the migration peak at the seller's then current list, which had moved 19 percent above the contracted rate. The buyer paid an additional $2.7M for capacity that returned to baseline within three weeks. The Desk wrote a clause rewrite into the 2026 renewal that converted the measurement to a windowed average and capped the true up rate at the contracted rate plus an explicit escalator. The 2026 term carried the same operational pattern with a reconciliation invoice 78 percent lower than the 2025 invoice would have produced under the prior clause.

A regional bank in EMEA discovered the asymmetry in the opposite direction. The bank had contracted a vSAN floor in 2023 against projected growth that did not materialise. By year two, actual capacity was running 18 percent below the floor. The clause as drafted gave the buyer no credit for the underconsumption. The 2026 rewrite introduced a true down provision and recovered roughly 11 percent of the term value through a credit applied at the next reconciliation.

The takeaway

• The vSAN capacity true up clause as standardly drafted is a one way ratchet. The headline rate is the floor of what the buyer pays. Every reconciliation moves the bill upward, never downward.
• Three rewrites convert the clause to a symmetric reconciliation. Lock the true up rate to the contract rate plus a bounded escalator. Change the measurement from peak to windowed average. Add a true down provision for sustained underconsumption.
• The clause is writable in two cycles of negotiation. The seller resists procedurally, then narrows the terms, then accepts a constrained version. The yield runs 11 to 19 percent of term value across the contracts we have rewritten.