Thursday Sep 03, 2009

Improved sd.conf format

Editing sd.conf has always been somewhat difficult thanks to it not being a documented interface and that the interface was never inteded to be exposed and it was even architecture specific. Fortunately Micheal documented it, which meant that it was known even if syntax remained obscure.

However after ARC case 2008/465 was approved and the changes pushed as part of bug 6518995 you can now use more a human readable syntax1:

sd-config-list=
        "ATA     VBOX HARDDISK", "disksort:false";

As it turns out the “disksort”2 option along with the thottle-max and throttle-min are the ones I most often want to tune.

Here is the current list of tunables lifted straight from the ARC case.


Tunable_Name

Commitment

Data_Type

cache-nonvolatile

Private

BOOLEAN

controller-type

Private

UINT32

delay-busy

Committed

UINT32

disksort

Private

BOOLEAN

timeout-releasereservation

Private

UINT32

reset-lun

Private

BOOLEAN

retries-busy

Private

UINT32

retries-timeout

Committed

UINT32

retries-notready

Private

UINT32

retries-reset

Private

UINT32

throttle-max

Private

UINT32

throttle-min

Private

UINT32


1This reminds me of the change to /etc/printcap that allowed you to specify the terminal flags as strings rather than as a bitmap. All the mystery seemed to be removed!

2While I used disksort as an example for this case I can't think of any reason why you would have it enabled for a virtual disk in VirtualBox.

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This is the old blog of Chris Gerhard. It has mostly moved to http://chrisgerhard.wordpress.com

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