[Gluster-devel] Question about unify over afr

[Łukasz Mierzwa]

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 

-- 
Łukasz Mierzwa

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