Re: best settings for usb2 and attached disks, and sdcards

On Wed, 2018-03-07 at 06:15 +0000, John wrote:
> Hi,
> [cc'd to arm_at_ and fs_at_ where it's also relevant]
> 
> I have a number of rpi3 & rpi3 machines. Usually I want to attach a usb keydrive to them so that the sdcard isn't thrashed. They're all running -current. usr/src and usr/ports at least are mounted on the keydrive.
> 
> When initially updating eg the ports tree, svn will time out/crash because of the poor write performance of these devices in a rpi2/3 context. The fs on the usb keys is always ufs2. I have tried mounting these devices as -o async and also in fstab but this parameter seems not to 'take' in that mount doesn't report the async property set:
> 
> [...]
> /dev/da0p2 on /ext (ufs, local, noatime, soft-updates)
> [...]
> 
> was mounted with the command "mount -o async,noatime,rw /dev/da0s2 /ext"
> but I can't tell if async is on or just ignored, no error message. And I still have to run svnlite cleanup /ext/ports until svnlite stops bailing out. When newfs was written, I passed -t  to it to enable trim, which seems to make a difference on this for deletes but not writes. Can anyone please suggest anything I can so to speed up disk i/o? And is async being applied or ignored?
> 
> thanks,

If your ufs2 filesystem is formatted with soft dependencies, the async
mount option does nothing (the ufs mount code forces it off when the
softdeps flag is on).  Basically, softdeps IS async for ufs.

If you have journaling enabled on the usb or sdcard filesystems, turn
it off.  It just amplifies the writes to devices that are already very
slow on writes, and the only benefit to journaling is that it speeds up
fsck recovery.  Since sdcard and thumb drive filesystems tend to be
very small already, the speed up from having journaling enabled amounts
to a few seconds at best, and even that benefit only comes after a
crash.

-- Ian