[OmniOS-discuss] puzzlingly slow disk access

[Eric Sproul]

Michael,
The SATA ports on this system appear to be operating in
legacy/compatible/IDE mode (note the lack of a "t" section in, e.g.
c3d0s0).  Disk performance in this mode is pretty poor.  It would be
preferable to have the SATA ports in native/AHCI mode, but in the case of
the rpool that will change the device names and leave you with an
unbootable system.  You can 1) backup and restore your system after
switching the SATA mode to native/AHCI, 2) just do a fresh reinstall after
switching modes or 3) attempt to fix up the various places where the device
paths are embedded (these paths are what change when the mode changes).
 For #3, see
http://mail.opensolaris.org/pipermail/zfs-discuss/2011-July/049175.html for
hints.

Eric


On Sun, Dec 30, 2012 at 5:50 PM, Michael Mounteney
<gate03 at landcroft.co.uk>wrote:

> I'm trying to nail down extremely poor NFS and even local disk access.
>
> Sun Fire X2250, dual SATA 7200 RPM 250 GiB, thus:
>
>         root at world:~# zpool status
>           pool: rpool
>          state: ONLINE
>           scan: resilvered 180G in 3h19m with 0 errors on Sun Dec 30
> 16:01:08 2012
>         config:
>
>                 NAME        STATE     READ WRITE CKSUM
>                 rpool       ONLINE       0     0     0
>                   mirror-0  ONLINE       0     0     0
>                     c3d0s0  ONLINE       0     0     0
>                     c4d0s0  ONLINE       0     0     0
>
>         errors: No known data errors
>
> Even that resilvering looks slow to me.  Now I know this isn't a
> definitive test but
>
>         dd if=15GiBVDIfile of=copy bs=10240k
>
> copies at 9.7 MB/s.  Surely that's around 1/6th of what it should be ?
>  That's in either the global or a child zone.
>
> --
> _________________
> Michael Mounteney
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>
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