Determining sufficient space for dedupe conversion

File Service Administration Guide for Hitachi NAS Platform
Version
14.9.x
Audience
anonymous
Part Number
MK-92HNAS006-31
File systems that have not been formatted with dedupe support must be converted before they will support deduplication. However, the conversion process is an offline process which can sometimes fail because there is not sufficient scratch or free space available. In this scenario, you must expand the file system and then re-attempt the conversion.
Note: File systems formatted or expanded in releases newer than dedupe will have the extra scratch space required for conversion and the following procedure is unnecessary.

Before you start the dedupe conversion, use the following procedure to determine if a file system has sufficient scratch and free space available. It is not an offline procedure.

  1. Call customer support to obtain the instructions and dev password to execute the fs-capacity-info dev command.
    This command can be run on a mounted file system.
  2. Run the command with the name of the file system that is to be checked (for example, fs-capacity-info f filesystem1).
    This command generates the following sample output: 
    fs-capacity-info/fs3: Underlying length : 0x017666400000 bytes, 0x00bb332000 sectors, 0x017666400 blocks 
fs-capacity-info/fs3: Formatted length : 0x017636000000 bytes, 0x00bb1b0000 sectors, 0x017636000 blocks 
fs-capacity-info/fs3: Scratch-space offset : 0x017636000000 bytes, 0x00bb1b0000 sectors, 0x017636000 blocks 
fs-capacity-info/fs3: Scratch-space length : 0x000030400000 bytes, 0x0000182000 sectors, 0x000030400 blocks 
fs-capacity-info/fs3: Reservable available space : 0x01748e51f000 bytes, 0x00ba4728f8 sectors, 0x01748e51f blocks 
fs-capacity-info/fs3: Physical available space : 0x0175ff4bb000 bytes, 0x00baffa5d8 sectors, 0x0175ff4bb blocks 
fs-capacity-info/fs3: Space required for RCB conversion : 0x0000e9e1c000 bytes, 0x000074f0e0 sectors, 0x0000e9e1c blocks 
fs-capacity-info/fs3: Scratch-space required for RCB conversion: 0x00002eccc800 bytes, 0x0000176664 sectors, 0x00002eccc blocks
  3. Locate the "Scratch-space length" value. In this example, 0x000030400000 bytes.
  4. Locate the "Scratch-space required for RCB conversion" value. In this example, 0x00002eccc800 bytes.
  5. If the Scratch-space length is greater than Scratch-space required for RCB conversion, then there is enough scratch space. In this example, 0x000030400000 is greater than 0x00002eccc800, indicating that there is enough scratch space for the conversion.
  6. Locate the "Reservable available space" value. In this example, 0x01748e51f000 bytes.
  7. Multiply the Space required for RCB conversion value by 1.6. In this example, the value is 0x000176360000 bytes.
  8. If Reservable available space is greater than Space required for RCB conversion * 1.6, then there is enough free space. 0x01748e51f000 is greater than 0x000176360000, indicating there is enough free space for the conversion.