Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Tue, 17 Jun 2008, William Francis wrote:
>
> I upgraded my drbd kernel module and userland tools to 8.0.12 and added the
> two additional parameters to my disk section of my drbd.conf as Lee
> suggested and wow, a full 10X improvement in write speed, which is about 60%
> of bare metal speed.
>
> What does this suggest? Does 8.0.11 have some performance ....um, issues (or
(my bad, I sent this from an unsubscribed address, hopefully it will not
show up twice...)
this has all been covered on the list...
Date: Sat, 24 May 2008 21:35:10 +0200
From: Philipp Reisner <philipp.reisner at linbit.com>
To: drbd-user at linbit.com
Subject: Re: [DRBD-user] 8.x performance vs 0.7x --- was (not urgent)
Request for DRBD Developers
[...]
> > > Personally, I'm still on 8.0.8. Later versions at the time seemed to
> > > show _VASTLY_ reduced performance on my hardware, so I excluded it
> > > from
> > > the updates. I'm not experiencing any problems, so I'm sticking with
> > > it.
That is due to that change:
8.0.9 (api:86/proto:86)
--------
* In case our backing devices support write barriers and cache
flushes, we use these means to ensure data integrity in
the presence of volatile disk write caches and power outages.
[...]
8.0.12 (api:86/proto:86)
--------
[...]
* Two new config options no-disk-flushes and no-md-flushes to disable
the use of io subsystem flushes and barrier BIOs.
[...]
But please *read* the documentation about "no-disk-flushes" and
understand the implications before you set these options.
# In case you are sure that your storage subsystem has battery
# backed up RAM and you know from measurements that it really honors
# flush instructions by flushing data out from its non volatile
# write cache to disk, you have double security. You might then
# reduce this to single security by disabling disk flushes with
# this option. It might improve performance in this case.
# ONLY USE THIS OPTION IF YOU KNOW WHAT YOU ARE DOING.
# no-disk-flushes;
# no-md-flushes;
-Phil
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