# Backup Summary Trend

**Purpose:** Backup capacity over time across the whole estate. Three series, used, free, and usable, plotted in GiB. It is the screen that answers whether you are going to run out of somewhere to put backups.

![Backup Summary Trend chart plotting used, free and usable backup capacity in gibibytes over a year](https://visualoneintelligence.com/wp-content/uploads/2026/08/voi-docs-backup-summary-trend.png)

## When to use it

- Establish the backup capacity growth rate for forecasting
- Confirm that added backup capacity actually landed
- Check whether a retention change had the effect it was supposed to
- Support a purchase case with a year of history rather than a snapshot

## Key areas and metrics

| Series | What it represents |
| --- | --- |
| Usable | Total backup capacity available |
| Used | How much of it holds backup data |
| Free | The remainder |

Data labels sit on the points, so exact figures are readable without hovering. The chart carries zoom presets, a save control, explicit date pickers, an export menu, and a range brush, with a grid beneath holding the same values per collection date.

## Reading step changes

Backup capacity rarely grows smoothly. It moves in steps, because capacity is added in appliances and retention changes take effect all at once. That makes this chart easier to interpret than most trend screens: each step corresponds to a specific event.

- **Usable jumps, used holds.** Capacity was added. Free space rises by the same amount.
- **Used falls sharply, usable holds.** Retention was shortened or a large dataset was expired.
- **All three move together.** An appliance was added or removed from collection, which changes the totals without anything happening to the data.
- **Used rising while free approaches zero.** The one that needs action, and the slope tells you how long you have.

Because deduplication and compression sit behind these figures, used capacity does not track protected data one for one. A month where protected data grew substantially can show a modest used increase, and that is the deduplication working rather than an error.

## Common actions

- **Use All for the shape, then a shorter preset for the current rate.** Long-run steps and recent slope answer different questions.
- **Project the used line against the usable line** to get an exhaustion estimate, and take the result to a purchase conversation rather than a capacity alert.
- **Correlate steps with change records.** An unexplained step in this chart usually means a collection change nobody logged.
- **Save the view** so each review reads the same window.

## Tips

> A sharp dip and immediate recovery in all three series is a collection gap, not a capacity event. Backup capacity does not halve overnight and return. Check the collection logs before investigating anything else.

## Related screens

[Backup Pool Summary](https://visualoneintelligence.com/docs/backup-pool-summary/) breaks the total down to individual pools. [Backup Pool Trend](https://visualoneintelligence.com/docs/backup-pool-trend/) is the same chart scoped to one pool. [Backup Host Occupancy](https://visualoneintelligence.com/docs/backup-host-occupancy/) shows which clients are consuming the capacity.

---

Source: https://visualoneintelligence.com/docs/backup-summary-trend/