[Unionfs] disable unionfs cache?

[Pásztor Lénárd Zoltán]

OOPS.
I missed the nfs layers set to nfs ro on this test session.
So I repeat the test sorry...

2007/7/16, Pásztor Lénárd Zoltán <lenard.pasztor at gmail.com>:
>
>
>
>
> > Lenard, what version of Unionfs have you been using?  I assume by
> > "newest"
> > you mean something in which we added the mtime-based cache-coherency
> > support.  Are you?  All of our recent releases include that automatic
> > cache-coherency support.
>
>
> v2.0, 2.6.22.1-u1
>
> >
> >
> > One possibility is that you mount unionfs on top of nfs mounts, and the
> > nfs
> > mounts don't reflect server-side changes fast enough for you?  This
> > would be
> > an NFS issue, since it caches attributes from the server onto the
> > client,
> > and doesn't purge them frequently enough.  In that case, I'd recommend
> > that
> > you mount all of your NFS mounts with "-o noac" (No Attribute Cache), or
> >
> > play with the four options ac{reg,dir}{min,max}.
> >
> > In other words, if the lower file system doesn't see new objects' data
> > and
> > attributes (esp. mtime/ctime), then Unionfs, sitting above, cannot see
> > them
> > either -- thus you have to first make the lower file systems see the
> > updated
> > file attributes.
>
>
> My test config:
> 2 nfs servers loadbalanced via LVS. Backend filesystem is ocfs2 on top of
> a drbd 0.8. block device (primary/primary config)
> This is for HA.
>
> Clients have an initrd. Initrd mounts the root filesystem.
> NFS related kernel command line opions:
> nfsroot=10.0.3.2:/storage,soft,noac
>
> #nfs root mounted by kernel internally at boot time (autoconfig):
> nfs:/storage /root nfs
> ro,sync,vers=3,rsize=8192,wsize=8192,acregmin=0,acregmax=0,acdirmin=0,acdirmax=0,soft,noac,nolock,proto=tcp,timeo=7,retrans=3,sec=sys,addr=
> 10.0.3.2 0 0
>
> # local storage for write support
> /dev/disk/by-label/local /union_local ext3 rw,data=ordered 0 0
>
> # 'new' root filesystem by unionfs (mounted by initrd)
> unionfs / unionfs
> rw,dirs=/union_local=rw:/root/layers/by-host/app1=ro:/root/layers/by-role/app=ro:/root/systems/current=ro
> 0 0
>
> There is only one nfs export ( /storage ), but the union branches has 3
> nfs layer. This layers are in the same nfs mount's sub directories.
>
> The nfs export (/storage) hierarchy:
> /layers
> /layers/by-host/app1
> /layers/by-host/app1/etc
> /layers/by-host/app1/etc/hostname "app1"
> /layers/by-role/app
> /layers/by-role/app/etc
> /layers/by-role/app/etc/hostname "app"
> /systems
> /systems/current/
> /systems/current/bin
> /systems/current/boot
> /systems/current/dev
> ...
> /systems/current/etc/hostname "base-system"
> ...
>
> For testing all layer has the /etc/hostname file.
> The local storage is empty ext3 filesystem.
> So, when the client boots it sets the hostname from by-host branch to
> "app1".
>
> (nfs)$cat /storage/layers/by-host/app1/etc/hostname
> app1
>
> (client)$cat /etc/hostname
> app1
> # from /storage/layers/by-host/app1/etc/hostname. It's ok.
>
>
> (nfs)$echo "xyz" > /storage/layers/by-host/app1/etc/hostname
> (nfs)$cat /storage/layers/by-host/app1/etc/hostname
> xyz
>
> (client)$cat /etc/hostname
> app1
> # It not changed on client side. :(
>
> (server)$rm /storage/layers/by-host/app1/etc/hostname
> # source deleted from by-host branch
>
> (client)$cat /etc/hostname
> app
> # from /storage/layers/by-role/app/etc/hostname. It's ok.
>
> (nfs)$echo "xyz" > /storage/layers/by-host/app1/etc/hostname
> # the /storage/layers/by-host/app1/etc/hostname now exists
>
> (client)$cat /etc/hostname
> app
> # client site not changed :(
>
> (server)$rm /storage/layers/by-role/app/etc/hostname
>
> (client)$cat /etc/hostname
> xyz
> # from /storage/layers/by-host/app1/etc/hostname. It's ok.
>
>
>
> --
> thx,
>
> Lénárd




-- 
üdv,

Lénárd
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