[LU-19547] FLR-EC: lfs setstripe support for erasure coding

• Type: Technical task
• Resolution: Unresolved
• Priority: Medium
• Severity: 3
• Assignee: Patrick Farrell
• Reporter: Patrick Farrell

Description

The lfs setstripe command needs to be able to create erasure-coded (EC) layouts.

Here's the current functionality as implemented in https://review.whamcloud.com/c/fs/lustre-release/+/61965

    Add support for Erasure Coding (EC) layouts in lfs setstripe
    using simple "X+Y" notation where X is data stripe count and Y
    is parity stripe count.

    When --ec is specified, an EC parity mirror is automatically
    created that matches the data mirror's component structure.
    The --ec option can appear anywhere in the command line and
    supports both single and multiple component layouts.

    EC Propagation Rules:
    - Single --ec applies to all components in the parity mirror
    - Multiple --ec values propagate bidirectionally: each spreads
      forward to the next --ec (or end) and backward to the
      previous --ec (or start)
    - Parity components automatically inherit extents from
      matching data components

    Usage examples:
      # Single component with EC(8+2)
      lfs setstripe -E -1 -c 8 --ec 8+2 /mnt/lustre/file

      # Order independent (--ec can appear anywhere)
      lfs setstripe --ec 8+2 -E -1 -c 8 /mnt/lustre/file

      # Multiple components, single EC spec (both get EC 8+2)
      lfs setstripe -E 128M -E -1 --ec 8+2 /mnt/lustre/file

      # Different EC for different components
      lfs setstripe -E 128M --ec 4+2 -E -1 --ec 8+2 /mnt/lustre/file

      # Long form option
      lfs setstripe --ec-stripe-count 4+2 -E -1 /mnt/lustre/file

Issue Links

• has to be done before: LU-19490 FLR-EC: Add/modify conf-sanity test_32 for erasure coding