<!--
{
  "availability" : [
    "DriverKit: 21.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "BlockStorageDeviceDriverKit",
  "identifier" : "/documentation/BlockStorageDeviceDriverKit/IOUserStorageOptions",
  "metadataVersion" : "0.1.0",
  "role" : "Type Alias",
  "symbol" : {
    "kind" : "Type Alias",
    "modules" : [
      "BlockStorageDeviceDriverKit"
    ],
    "preciseIdentifier" : "c:@T@IOUserStorageOptions"
  },
  "title" : "IOUserStorageOptions"
}
-->

# IOUserStorageOptions

Options that affect the performance of read-write operations.

```
typedef uint32_t IOUserStorageOptions;
```

## Discussion

Use these options with the [`DoAsyncReadWrite`](/documentation/BlockStorageDeviceDriverKit/IOUserBlockStorageDevice/DoAsyncReadWrite) function.

## Topics

### Storage Options

[`#define kIOUserStorageOptionNone`](/documentation/BlockStorageDeviceDriverKit/kIOUserStorageOptionNone)

A value that defines no options.

[`#define kIOUserStorageOptionForceUnitAccess`](/documentation/BlockStorageDeviceDriverKit/kIOUserStorageOptionForceUnitAccess)

An option to use Force Unit Access (FUA).


---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)