GPT vs MBR for swap devices

Mark Millard marklmi at
Fri Jun 15 20:19:07 UTC 2018

On 2018-Jun-15, at 9:42 AM, bob prohaska <fbsd at> wrote:

> On Fri, Jun 15, 2018 at 09:57:17AM -0600, Warner Losh wrote:
>> gstat -Bd -I 10 -f <regexp for your swap partition>  > gstat-swap-data.dat
>> would be how I'd recommend collecting it. This file may get kinda big
>> depending how long it takes to trigger the weird state. I'm hoping that if
>> you put this on a known good device, we'll power through the issues. We
>> might not get perfect correlation with this, but the data should show all
>> kinds of crazy before the system drives off the cliff if I'm right, so we
>> don't need perfect data.
> Apologies,  we spoke of gstat earlier. I lost the distinction between
> gstat and vmstat. In the case at hand the possible swap devices are
> /dev/da0b (this is the one causing trouble)
> /dev/mmcsd0s3b
> /dev/mmcsd0s3d
> what would the correct <regexp> look like?
> Is there any indication why problems seen on the RPI3 do not seem
> apparent on an RPI2? A 2 GB USB flash swap partition seems to work
> successfully on the Pi2.

gstat and top/swapinfo are good for different things:

gstat: for various I/O rates and such to the swap partition(s)

top: for samples of how much swap space is in use (total).
swapinfo: per swap partition swap space usage and the total.
(swapinfo requires use of separate looping/sleeping for it to
repeatedly report.)

(swapinfo is a specialization/limitation of pstat.)

There may be times when you want information about both
aspects (I/O rates and usage-size figures from similar time

Mark Millard
marklmi at
( went
away in early 2018-Mar)

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