Faster SVM mirror resync

With Solaris Volume Manager (SVM), RAID 1 volumes (mirroring) can benefit from increased sync buffer_size of 1M. The default settings in Solaris Volume Manager can lead to pretty long resync times, and the way to speed it up is [taken straight out of the metasync(1M) manpage]

There are two way to change block size to get quickly synchronized disks in mirrored system

via command-line

Use the metasync -r buffer_size

buffer_size Specifies the size (number of 512-byte disk blocks) of the internal copy buffer for the mirror resync. The size defaults to 128 512-byte disk blocks (64 Kbytes). It can be no more than 2048 blocks. For best performance (quickest completion of the resync), 2048 blocks is the recommended size.

For example:

# metasync -r 2048

For permanent changes

  • Solaris 8 / Solaris 9
    Edit the /etc/rc2.d/S95svm.sync file to include the 2048 buffer_size.
  • Solaris 10
    • Add the following line to /etc/system, set
      md_mirror:md_resync_bufsz = 2048
    • Perform a system reboot


  • The maximum buffer_size is 2048
  • Increasing the value will may lead low I/O performance.