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2.2.1: SAVE fails - main index checkpoint buffer only 512-byte aligned on 4096-sector device (NativeStorageDevice misaligned I/O)

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#2,239 2 comments 0 reactions 1 assignee View on GitHub

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@TedHartMS is already working on this.

Since Oct 13, 2026.

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Description

Summary

On Garnet 2.2.1, SAVE fails because the main index checkpoint write is rejected as misaligned. The file offset and length are both 4096-aligned. The in-memory staging buffer is not: it sits on a 512-byte boundary while the device sector size is 4096.

Environment
  • Image ghcr.io/microsoft/garnet:2.2.1, Linux, default device type (native O_DIRECT path).
  • Data directory on a ZFS dataset that reports a 4096-byte sector size.
Steps
  1. Start Garnet 2.2.1 with its data directory on a 4096-byte-sector filesystem.
  2. Write some keys.
  3. Run SAVE.
Actual result

The client receives ERR checkpoint failed, check server logs. The server log contains:

TsavoriteKV BeginMainIndexCheckpoint failed … NativeStorageDevice.WriteAsync: misaligned I/O — sector size is 4096, but offset=0x0, length=134217728, buffer=0x00007F2D74000200. All three values must be a multiple of the device sector size for the O_DIRECT / libaio / io_uring path.

0x...0200 is 512-aligned but not 4096-aligned. The offset (0x0) and length (128 MiB) are both aligned, so the failure is the index checkpoint buffer's alignment.

Expected result

When the device reports a 4096-byte sector, the checkpoint buffer should be allocated with the device's sector alignment, and SAVE should succeed.

Workaround

We are switching to --device-type FileStream, which does not use O_DIRECT. We will confirm in a comment whether that works.

Related

This looks like the same native checkpoint I/O path as #2134 and #2228

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