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# FSVolume.PreallocateOperations

Methods and properties implemented by volumes that want to offer preallocation functions.

```
protocol PreallocateOperations : NSObjectProtocol
```

## Overview

A preallocation operation allocates space for a file without writing to it yet.
A file system may use reallocation to avoid performing space allocation while in the midst of I/O; this strategy improves performance.
Also, if the expected I/O pattern is many small writes, preallocating contiguous chunks may prevent fragmenting the file system.
This process can improve performance later.

In a kernel-based file system, you typically preallocate space with the `VNOP_ALLOCATE` operation, called from `fcntl(F_PREALLOCATE)`.

> Deprecated: Use ``doc://FSKit/documentation/FSKit/FSVolume/PreallocateHandler`` instead.

## Topics

### Preallocating space

[`preallocateSpace(for:at:length:flags:replyHandler:)`](/documentation/FSKit/FSVolume/PreallocateOperations/preallocateSpace(for:at:length:flags:replyHandler:))

Preallocates disk space for the given item.

[`FSVolume.PreallocateFlags`](/documentation/FSKit/FSVolume/PreallocateFlags)

Behavior flags for preallocation operations.

### Inspecting volume properties

[`isPreallocateInhibited`](/documentation/FSKit/FSVolume/PreallocateOperations/isPreallocateInhibited)

A Boolean value that instructs FSKit not to call this protocol’s methods, even if the volume conforms to it.


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