Re: NetBSD disk I/O

[Andy Ball <ball%grex.org@localhost>]

Hello Michael,

  MvE> Can you verify partition alignment? Modern disks require an
     > alignment of 4kbyte (8 sectors), otherwise all write
     > operations are executed as slow read-modify-write cycles.

You're right: this is a 4K disk...

    Model: HGST HTS545025A7E380, Rev: GGEOAC90
    Capacity 250 Gbytes, 488397168 sectors, 512 bytes/sector
    Physical sector size: 4096 bytes

  ...and partition alignment seems to make a difference...

    Start   Write
    Sector  MB/S
    ~~~~~~  ~~~~~~
       0     5.0
       1     3.6
       2     3.6
       3     3.6
       4     3.5
       5     3.5
       6     3.9
       7     3.9

       8     4.9

I'll test the other disks to see whether they're all 4K
sectored models.

Thanks,
  - Andy Ball