Re: [vserver] vhashify not working? - 2.6.27.14-vs2.3.0.36.4

From: John A. Sullivan III <jsullivan_at_opensourcedevel.com>
Date: Tue 31 Mar 2009 - 09:08:37 BST
Message-Id: <1238486917.6546.9.camel@jaspav.missionsit.net.missionsit.net>

On Tue, 2009-03-31 at 06:51 +0000, Christoph Lukas wrote:
> Hi John,
>
> > Hello, all. In our earlier deployments on kernel 2.6.22, we were very
> > happy with the results of vhashify. For some reason, our use in
> > 2.6.27.14 using vserver 2.3.0.36.4 does not seem to be working as well.
> > This is important to us because we are planning roughly 400 nearly
> > identical guests on this one host.
> >
> > We currently have 10 Ubuntu 8.0.4 guests running on our CentOS 5.2 based
> > host. Each one is roughly 2GB in size and were all cloned from the same
> > template. Total storage on the vserver partition is roughly 21GB. The
> > only unusual bit about this installation is there is /vservers/vetc
> > directory which is then mounted via bind to /etc/vservers. This was
> > originally because there was a single encrypted partition mounted via
> > iSCSI holding all the vserver information.
> >
> > We've done:
> > mkdir /etc/vservers/.defaults/apps/vunify/hash /vservers/.hash
> > ln -s /vservers/.hash /etc/vservers/.defaults/apps/vunify/hash/root
> >
> > We noticed there is another
> > link, /etc/vservers/.defaults/apps/vunify/hash/00
> > and hashify complained of a duplicate "root"directory so we deleted the
> > root symlink. With or without it, we have the same results.
>
> are there any hardlinks visible inside the /vservers/.hash directory? If
> not the hashify did not work.
>
> You can check which files inside the vservers are not unified by running
>
> find /vserver/<guest> -type f -links 1
>
> and the unified files by running:
>
> find /vserver/<guest> -type f -links +1
>
> This should give you a hint if vhashify worked correctly.
>
> > For each vserver guest, we did:
> > mkdir /etc/vservers/<name>/apps/vunify
> >
> > Has something changed with 2.6.27.14?
>
> AFAIK unification is just done in userspace it should not depend on the
> kernel version. Just the copy-on-write-link-breakage is done in the
> kernel.
>
> > Are these realistic numbers?
>
> Does not seem realistic to me.
>
> > I
> > would think ten identical systems should yield just slightly more than
> > the space of one system after running hashify.
>
> I would guess something with your .hash directories is not setup
> correctly and therefore the hashify did nor work as expected. You can
> try to fix this and then just run:
>
> vserver <guest> hashify
>
> on a running guest. I have setup unification successfully here and used
> this two wiki pages as howto:
>
> http://linux-vserver.org/Frequently_Asked_Questions#Unification
>
> http://linux-vserver.org/util-vserver:Vhashify
>
> Hope this helps,
> Christoph
>
Thank you, Christoph. The commands show plenty of both types of files
with the hard links clearly outweighing the regular files. Strange that
I still show 20GB for 10 servers. Take care - John

-- 
John A. Sullivan III
Open Source Development Corporation
+1 207-985-7880
jsullivan@opensourcedevel.com
http://www.spiritualoutreach.com
Making Christianity intelligible to secular society
Received on Tue Mar 31 09:07:18 2009
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