RamDisk query

1. Parameters registry is

HKLM\System\CurrentControlSet\Services\RRamdisk\Parameters\

Why RRamdisk? Because XP SP1 contain a Ramdisk driver for XP Embeded.
2. Parameter: DiskSizeM, DiskSizeK

Your desired disk size, the unit is M bytes or K bytes. The DiskSizeK has higher priority.
3. Parameter: MediaType

The reported drive type:

1 — RAM Drive
2 — Fixed Media (default)
3 — Removable Media
4 — Floppy Diskette
4. Parameter: DriveLetter

Name say it is, default is R:
5. Parameter: SectorsPerCluster

Your desired cluster size, zero for driver pickup:

<= 2M FAT12, cluster=512
<= 32M FAT16, cluster=512
<= 64M FAT16, cluster=1k
<= 128M FAT16, cluster=2k
<= 256M FAT16, cluster=4k
<= 512M FAT32, cluster=2k
<= 16G FAT32, cluster=4k
and more...

You can specify smaller cluster size, force pre-format as FAT32.
6. Parameter: Image

Maintained by rdutil utlilty, mainly for preload NTFS image. Eg:
1. Load ramdisk, don’t write anything.
2. Format the ramdisk

FORMAT /FS:NTFS /Q /V:RamDisk /A:512 R:
3. Adjust logfile to minimum size

CHKDSK /L:2048 R:
4. Reset access rights

CACLS R:\ /G: BUILTIN\Adminstrators:F
5. Create necessary structure

MKDIR R:\TEMP
6. Pack the disk image and save to registry

rdutil R: registry

Notes:
1. You should leave RamDisk as clean as possible before packing, the max packed image size is 64K.
2. The disk image only valid to same RamDisk size, you should re-create disk image when size changed.
3. The driver internal formater will disable if this registry present, corrupt/size-mismatch value leave an un-formated disk.

rdutil Utlility Usage:
1. Backup registry image

rdutil save filename
2. Restore registry image

rdutil load filename
3. Report packed image size

rdutil R:
rdutil registry
rdutil unpacked_file

Second command reading DriveLetter from registry, while the third is packing an unpacked image file.
4. Packing image & save to registry

rdutil R: registry
5. Packing image & save to file

rdutil R: packed_file
6. Unpacking image

rdutil unpack packed_file unpacked_file
7. Link NTFS junction to Ramdisk

rdutil link temp \
7. You can re-format RamDisk except RAMDrive media type. Eg:

FixedMedia type:
FORMAT /FS:NTFS /FORCE /Q /V:RamDisk /A:512 R:

RemovableMedia type:
ECHO Y | FORMAT /FS:NTFS /FORCE /Q /V:RamDisk /A:512 R:

You can place your format command to startup script. I don’t recommend re-format to FAT, the pre-formated RamDisk is more efficient than other format utililty.
8. Pagefile support - You can set pagefile to FixMedia type disk w/ pre-formated system. If you need other MediaType or re-format, use the addswap.exe utility:

addswap r:\pagefile.sys 16 32

Create pagefile r:\pagefile.sys with min=16M max=32M.
9. TEMP directory - You should set TEMP/TMP directory to TEMP sub-directory, don’t use the root directory.
10. NTFS junction point to RAMDrive - You can’t create NTFS junction point to RAMDrive media type, Fixed & Removable Media type should work.
11. Connectix VirtualPC compatibility - Someone report problem with VirtualPC+physical volume/disk. Please set MediaType to RAMDrive/Removable.
12. Mountpoint without DriveLetter

Clear DriveLetter registry value will not create Drive Letter for Ramdisk.

Attn. Don’t delete the DriveLetter registry, which fall to default R:. You can setup mountpoint/junction linking to this unnamed Ramdisk. Eg:

rdutil link C:\ramdisk
link C:\ramdisk to root of Ramdisk

rdutil link C:\TEMP TEMP
link C:\TEMP to \TEMP at Ramdisk

rmdir C:\ramdisk
rmdir can remove the link without clear target content

NoDriveLetter configuration isn’t recommended, because most AntiVirus software cannot realtime scan Volume w/o Drive Letter.


that is from the utility