Re: Time to increase MAXPHYS?

From: Hans Petter Selasky <hps_at_selasky.org>
Date: Sun, 4 Jun 2017 09:52:36 +0200
On 06/04/17 09:39, Tomoaki AOKI wrote:
> Hi
> 
> One possibility would be to make it MD build-time OTIONS,
> defaulting 1M on regular systems and 128k on smaller systems.
> 
> Of course I guess making it a tunable (or sysctl) would be best,
> though.
> 

Hi,

A tunable sysctl would be fine, but beware that commonly used firmware 
out there produced in the millions might hang in a non-recoverable way 
if you exceed their "internal limits". Conditionally lowering this 
definition is fine, but increasing it needs to be carefully verified.

For example many USB devices are only tested with OS'es like Windows and 
MacOS and if these have any kind of limitation on the SCSI transfer 
sizes, it is very likely many devices out there do not support any 
larger transfer sizes either.

--HPS
Received on Sun Jun 04 2017 - 05:54:50 UTC

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