Registry Settings for FATFS Disk Caching
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8/28/2008
This topic covers registry settings control disk cache behavior for file allocation table (FAT) file systems.
For All Platforms:
The following values can be placed at the following locations in the registry:
- Root file system key
Settings made at the root key of the file system registry, HKEY_LOCAL_MACHINE\System\StorageManager\FATFS, apply to every mounted instance of FATFS, unless explicitly overridden by a setting at a lower level. These setting apply to FATFS for all profiles. - Profile-specific settings
Settings made at the Profiles registry subkey, HKEY_LOCAL_MACHINE\System\StorageManager\Profile\<MyProfileName>\FATFS, apply only to devices that report the profile <MyProfileName>.
The following table shows the registry settings.
| Registry Value/Type | Applies to | Description |
|---|---|---|
BitmapCacheSize: REG_DWORD |
Transaction-safe file allocation table (TFAT) |
Set to the size of the bitmap cache, in number of sectors. If set to zero, FATFS determines the best cache size to use. For more information, see CacheSize Registry Subkey. |
CacheDLL: REG_SZ |
FAT, TFAT |
Specifies the name of the disk cache library, such as diskcache.dll. |
CacheSize: REG_DWORD |
Obsolete |
This value is obsolete.
Do not use in Windows CE 5.0 and later.
Do not use in Windows Mobile Version 5.0 and later.
Replace with FatCacheSize or DataCacheSize. Indicates the size of the disk cache, in number of sectors. |
DataCacheSize: REG_DWORD |
FAT, TFAT |
Indicates the size of the data cache, in number of sectors. If set to zero, FATFS determines the best cache size to use. For more information, see CacheSize Registry Subkey. |
EnableBitmapCacheWarm: REG_DWORD |
TFAT |
Set to 1 to enable pre-warming of the bitmap cache. |
EnableCache: REG_DWORD |
FAT, TFAT, extended FAT (exFAT) |
Set to 1 to enable caching. Zero disables caching. |
EnableDataCacheWarm: REG_DWORD |
FAT, TFAT |
Set to 1 to enable pre-warming of the data cache. That is, on initialization, the cache is pre-loaded to capacity with data. |
EnableFatCacheWarm: REG_DWORD |
FAT, TFAT |
Set to 1 to enable pre-warming of the FAT cache. That is, on initialization, the cache is pre-loaded to capacity with data. |
EnableWriteBack: REG_DWORD |
FAT, TFAT |
Set to 1 to enable a write-back cache. Set to zero to use a write-through cache.
This setting applies only to Windows CE 5.0 and later.
This setting applies only to Windows CE 5.0 and later. |
FatCacheSize: REG_DWORD |
FAT, TFAT |
Set to the size of the FAT cache, in number of sectors. If set to zero, FATFS determines the best cache size to use. For more information, see CacheSize Registry Subkey. |
LazyWriterThreadPrio256: REG_DWORD |
FAT, TFAT |
Specifies the priority of the lazy write-back thread. |
Note
When you enable pre-warming of the FAT or data cache, you trade longer startup times for quicker cache access when fully booted. To determine the settings that offer the best performance for your device, experiment with different values for EnableFatCacheWarm and EnableDataCacheWarm.
For Windows Embedded CE:
| Registry Value/Type | Applies to | Description |
|---|---|---|
BitmapCacheSize: REG_DWORD |
exFAT |
Set to the size of the bitmap cache, in number of sectors. If set to zero, FATFS determines the best cache size to use. For more information, see CacheSize Registry Subkey. |
CacheDLL: REG_SZ |
exFAT |
Specifies the name of the disk cache library, such as diskcache.dll. |
DataCacheSize: REG_DWORD |
exFAT |
Indicates the size of the data cache, in number of sectors. If set to zero, FATFS determines the best cache size to use. For more information, see CacheSize Registry Subkey. |
EnableBitmapCacheWarm: REG_DWORD |
exFAT |
Set to 1 to enable pre-warming of the bitmap cache. |
EnableDataCacheWarm: REG_DWORD |
exFAT |
Set to 1 to enable pre-warming of the data cache. That is, on initialization, the cache is pre-loaded to capacity with data. |
EnableFatCacheWarm: REG_DWORD |
exFAT |
Set to 1 to enable pre-warming of the FAT cache. That is, on initialization, the cache is pre-loaded to capacity with data. |
EnableWriteBack: REG_DWORD |
exFAT |
Set to 1 to enable a write-back cache. Set to zero to use a write-through cache. This setting applies only to Windows CE 5.0 and later. |
FatCacheSize: REG_DWORD |
exFAT |
Set to the size of the FAT cache, in number of sectors. If set to zero, FATFS determines the best cache size to use. For more information, see CacheSize Registry Subkey. |
LazyWriterThreadPrio256: REG_DWORD |
exFAT |
Specifies the priority of the lazy write-back thread. |