My 2nd Head

There are two kernel parameters that can be adjusted if ZFS resilvering speed is too slow/fast: zfs_resilver_delay /* number of ticks to delay resilver */ and zfs_resilver_min_time_ms /* min millisecs to resilver per txg */ In some cases the values can be too low or two high (e.g. when using Mirroring vs. RAIDZ). A boost could be: # echo zfs_resilver_delay/W0|mdb -kw # echo zfs_resilver_min_time_ms/W0t3000|mdb -kw whereas a handbrake is e.g.: # echo zfs_resilver_delay/W2|mdb -kw # echo zfs_resilver_min_time_ms/W0t300|mdb -kw Disclaimer: Use at your own risk. Do not try on production systems without contacting support first.

Finding write operations for a process. Especially when writing to a NFS share... # dtrace -n 'fsinfo:::write /execname == " execname "/ \   { printf("%s", args[0]->fi_pathname) }' Finding the top userland stacks for a process # dtrace -n 'syscall:::entry /execname == " execname "/ \   { @[ustack()] = count();}' Finding the same for a certain system call # dtrace -n 'syscall::mmap:entry /execname == " execname "/ \   { @[ustack()] = count();}'