[Gluster-devel] Question about unify over afr

[Łukasz Mierzwa]

Friday 29 August 2008 20:21:57 Łukasz Mierzwa napisał(a):
> Friday 29 August 2008 20:13:45 Łukasz Mierzwa napisał(a):
> > Thursday 28 August 2008 15:29:06 Łukasz Mierzwa napisał(a):
> > > Thursday 28 of August 2008 12:39:03 napisałeś(-łaś):
> > > > On Thu, Aug 28, 2008 at 3:01 PM, Łukasz Mierzwa <l.mierzwa at grono.net>
> >
> > wrote:
> > > > > Thursday 28 of August 2008 07:06:30 Krishna Srinivas napisał(a):
> > > > >> On Wed, Aug 27, 2008 at 10:55 PM, Łukasz Mierzwa
> > > > >> <l.mierzwa at grono.net>
> > > > >
> > > > > wrote:
> > > > >> > Tuesday 26 August 2008 16:28:41 Łukasz Mierzwa napisał(a):
> > > > >> >> Hi,
> > > > >> >>
> > > > >> >> I testing glusterfs for small files storage, first I've setup a
> > > > >> >> single disk gluster server, connected to it from another
> > > > >> >> machine and served those files with nginx. That worked ok, I
> > > > >> >> got good performance, on average about +20ms slower for each
> > > > >> >> request but that's ok. Now I've setup unify over afr (2 afr
> > > > >> >> groups with 3 servers each, unify and afr on the client side,
> > > > >> >> namespace dir is on every server, as other stuff afr'ed on the
> > > > >> >> client side), this is mounted on one of those 6 servers. After
> > > > >> >> writing ~200GB files from production server I started to do
> > > > >> >> some tests and I've noticed that doing simple ls on that mount
> > > > >> >> point causes as many writes as reads, this has to do something
> > > > >> >> to either unify or afr, I suspect that those writes are do to
> > > > >> >> namespace but I need to do more debugging. It's very annoying
> > > > >> >> that simple reads are causing so many writes. All my servers
> > > > >> >> are in sync so there should not be any need for sealf-healing.
> > > > >> >> Before I start debugging it I wanted to ask if this is normal?
> > > > >> >> Shoud afr or unify generate so many writes to namespace or
> > > > >> >> maybe xattrs during reads (storage is on ext3 with users_xattrs
> > > > >> >> on)?
> > > > >> >
> > > > >> > I tested it a little bit today and I found out that if I got 1
> > > > >> > or 2 nodes in my afr group for namespace there are no writes at
> > > > >> > all while doing ls, if I add one or more nodes they are starting
> > > > >> > to get writes. WTF?
> > > > >>
> > > > >> Do you mean that your NS is getting write() calls when you do
> > > > >> "ls"?
> > > > >
> > > > > It seems so. I will split my NS and DATA bricks to different disks
> > > > > today so I will be 100% sure. What I am sure now is that I am
> > > > > getting as many writes as reads when I do "ls" and have more than 2
> > > > > NS bricks in AFR.
> > > >
> > > > reads/writes should not happen when you do an 'ls' where are you
> > > > seeing reads and writes being done? How are you seeing it? are you
> > > > strace'ing the glusterfsd?
> > > >
> > > > Krishna
> > >
> > > I first noticed them when I looked at rrd graphs for those machines, I
> > > wanted to see if AFR is balancing reads. I can see them in rrd graphs
> > > generated from collectd, dstat, iotop and iostat, they are happening. I
> > > first tried to find something in my config and forgot about such
> > > obvious step as straceing glusterfs. I attach log from one of the
> > > servers, I straced gluster-server on this machine, You can see that
> > > there is a lot of mkdir/chown/chmod on files that are already there,
> > > all bricks were online when I was writing files to gluster client so no
> > > self-heal should be needed. I've also attached client and server
> > > configs.
> >
> > I attached strace log from gluster-server, this time I removed all but
> > last two ns servers, I straced brick with ns, no mkdir/chmod this time.
>
> Missing attachment

Hmm, something is eating my attachments.
Grab it from:
http://doc.grono.org/gl_2ns.log.bz2

-- 
Łukasz Mierzwa

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