Strange I/O problem on Freenas 0.7.2

[lokadamus at gmx.de]

Freenas 0.7.2 is old.
Is write cache enable?
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/configtuning-disk.html

Is ZFS in use?
ZFS has a value for tuning.


On 22.10.2012 07:34, Henti Smith wrote:
> Hi all.
>
> I'm having a very weird problem with a friends Freenas set-up. I'm
> trying to backup his data before migrating to nas4free or just plain
> FreeBSD.
>
> The setup is as follows:
>
> HP Microserver N36.
> 2BG Mem (1713 MB Usable) (no swap)
> 4 x 2000GB (ST2000DL003-9VT166 Seagate) drives in a graid5 setup.
>
> Initially he had no problems with the setup. Samba share was fine and
> he populated the raid set with 3TB of data, but somewhere along the
> line the disk I/O went VERY slow.
>
> I initially thought this might be raid related and did some tests but
> actually found the problem to be on the discs.
>
> [root at freenas ~]# diskinfo -c /dev/ad4
> /dev/ad4
>          512             # sectorsize
>          2000398934016   # mediasize in bytes (1.8T)
>          3907029168      # mediasize in sectors
>          3876021         # Cylinders according to firmware.
>          16              # Heads according to firmware.
>          63              # Sectors according to firmware.
>          ad:5YD2VEWQ     # Disk ident.
>
> I/O command overhead:
>          time to read 10MB block      0.250736 sec       =    0.012 msec/sector
>          time to read 20480 sectors  79.653738 sec       =    3.889 msec/sector
>          calculated command overhead                     =    3.877 msec/sector
>
> [root at freenas ~]# diskinfo -t /dev/ad4
> /dev/ad4
>          512             # sectorsize
>          2000398934016   # mediasize in bytes (1.8T)
>          3907029168      # mediasize in sectors
>          3876021         # Cylinders according to firmware.
>          16              # Heads according to firmware.
>          63              # Sectors according to firmware.
>          ad:5YD2VEWQ     # Disk ident.
>
> Seek times:
>          Full stroke:      250 iter in 124.649884 sec =  498.600 msec
>          Half stroke:      250 iter in  52.112172 sec =  208.449 msec
>          Quarter stroke:   500 iter in 167.991252 sec =  335.983 msec
>          Short forward:    400 iter in  72.027133 sec =  180.068 msec
>          Short backward:   400 iter in 150.708625 sec =  376.772 msec
>          Seq outer:       2048 iter in   5.748059 sec =    2.807 msec
>          Seq inner:       2048 iter in 119.395823 sec =   58.299 msec
> Transfer rates:
>          outside:       102400 kbytes in  39.207296 sec =     2612 kbytes/sec
>          middle:        102400 kbytes in 113.757181 sec =      900 kbytes/sec
>          inside:        102400 kbytes in 153.438159 sec =      667 kbytes/sec
>
> S.M.A.R.T. is not reporting any issues either and the speeds are
> similar on all the drives. No errors in /var/log either.
>
> Any help or suggestions would be appreciated.
>
> Regards
> Henti
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