Gluster users - Aug 2008 - Sharing home directories between two symetric nodes?

Hello,

I just discovered Gluster a couple of weeks ago and went through the
initial documentation and got it compiled.

It looks very promising both for my home network and for work.

For now I'm concentrating at home -

We have to Ubuntu 8.04 desktops, one for me and one for my wife.

We generally try to keep them off when not used but at any time any
one of them could be up or down.

I was wondering whether Gluster would allow me to share our /home
partition so whichever host is currently up - it'll have the most
current /home partition with it. When both are up then both can write
to it and have the latest version locally.

Can Gluster do this?

I got a hunch that it is possible to just configure some /data/home
server volume which will be mirrored a-la "Automatic File Replication
(Mirror) across Two Storage Servers"
(http://www.gluster.org/docs/index.php/Automatic_File_Replication_(Mirror)_across_Two_Storage_Servers)
then mount /home on both same machines from that mirrored volume.

Does this make sense or did I get it all wrong?

If not, is there another way to achieve something like this?

Thanks,

--Amos

I think you have it right.
it''s an interesting way to use gluster..  you run a risk on occasion,
however.

if you happen to update files on both ends while they''re 
disconnected, then once you''re re-connected, when you access the same 
file, you can not be sure which version will prevail.

(you can, but it''s difficult to know--as I understand it, gluster 
tracks a timestamp and a revision number--somehow it uses these to 
decide which file is "newer")

Also, gluster doesn''t to automatic healing--meaning, when you 
reconnect it doesn''t immediately push the updates to the other side.. 
this is done only when files are accessed.  So, if you make file 
changes while disconnected, and then reconnect.. change some OTHER 
files, then disconnect again, you may still have an older version of 
the original file

those are my thoughts,
Keith

At 04:14 AM 8/1/2008, Amos Shapira wrote:
>Hello,
>
>I just discovered Gluster a couple of weeks ago and went through the
>initial documentation and got it compiled.
>
>It looks very promising both for my home network and for work.
>
>For now I''m concentrating at home -
>
>We have to Ubuntu 8.04 desktops, one for me and one for my wife.
>
>We generally try to keep them off when not used but at any time any
>one of them could be up or down.
>
>I was wondering whether Gluster would allow me to share our /home
>partition so whichever host is currently up - it''ll have the most
>current /home partition with it. When both are up then both can write
>to it and have the latest version locally.
>
>Can Gluster do this?
>
>I got a hunch that it is possible to just configure some /data/home
>server volume which will be mirrored a-la "Automatic File Replication
>(Mirror) across Two Storage Servers"
>(http://www.gluster.org/docs/index.php/Automatic_File_Replication_(Mirror)_across_Two_Storage_Servers)
>then mount /home on both same machines from that mirrored volume.
>
>Does this make sense or did I get it all wrong?
>
>If not, is there another way to achieve something like this?
>
>Thanks,
>
>--Amos
>
>_______________________________________________
>Gluster-users mailing list
>Gluster-users at gluster.org
>http://zresearch.com/cgi-bin/mailman/listinfo/gluster-users

I think you have it right.
it''s an interesting way to use gluster..  you run a risk on occasion,
however.

if you happen to update files on both ends while they''re 
disconnected, then once you''re re-connected, when you access the same 
file, you can not be sure which version will prevail.

(you can, but it''s difficult to know--as I understand it, gluster 
tracks a timestamp and a revision number--somehow it uses these to 
decide which file is "newer")

Also, gluster doesn''t to automatic healing--meaning, when you 
reconnect it doesn''t immediately push the updates to the other side.. 
this is done only when files are accessed.  So, if you make file 
changes while disconnected, and then reconnect.. change some OTHER 
files, then disconnect again, you may still have an older version of 
the original file

those are my thoughts,
Keith

At 04:14 AM 8/1/2008, Amos Shapira wrote:
>Hello,
>
>I just discovered Gluster a couple of weeks ago and went through the
>initial documentation and got it compiled.
>
>It looks very promising both for my home network and for work.
>
>For now I''m concentrating at home -
>
>We have to Ubuntu 8.04 desktops, one for me and one for my wife.
>
>We generally try to keep them off when not used but at any time any
>one of them could be up or down.
>
>I was wondering whether Gluster would allow me to share our /home
>partition so whichever host is currently up - it''ll have the most
>current /home partition with it. When both are up then both can write
>to it and have the latest version locally.
>
>Can Gluster do this?
>
>I got a hunch that it is possible to just configure some /data/home
>server volume which will be mirrored a-la "Automatic File Replication
>(Mirror) across Two Storage Servers"
>(http://www.gluster.org/docs/index.php/Automatic_File_Replication_(Mirror)_across_Two_Storage_Servers)
>then mount /home on both same machines from that mirrored volume.
>
>Does this make sense or did I get it all wrong?
>
>If not, is there another way to achieve something like this?
>
>Thanks,
>
>--Amos
>
>_______________________________________________
>Gluster-users mailing list
>Gluster-users at gluster.org
>http://zresearch.com/cgi-bin/mailman/listinfo/gluster-users

I think you have it right.
it's an interesting way to use gluster..  you run a risk on occasion,
however.

if you happen to update files on both ends while they're 
disconnected, then once you're re-connected, when you access the same 
file, you can not be sure which version will prevail.

(you can, but it's difficult to know--as I understand it, gluster 
tracks a timestamp and a revision number--somehow it uses these to 
decide which file is "newer")

Also, gluster doesn't to automatic healing--meaning, when you 
reconnect it doesn't immediately push the updates to the other side.. 
this is done only when files are accessed.  So, if you make file 
changes while disconnected, and then reconnect.. change some OTHER 
files, then disconnect again, you may still have an older version of 
the original file

those are my thoughts,
Keith

At 04:14 AM 8/1/2008, Amos Shapira wrote:
>Hello,
>
>I just discovered Gluster a couple of weeks ago and went through the
>initial documentation and got it compiled.
>
>It looks very promising both for my home network and for work.
>
>For now I'm concentrating at home -
>
>We have to Ubuntu 8.04 desktops, one for me and one for my wife.
>
>We generally try to keep them off when not used but at any time any
>one of them could be up or down.
>
>I was wondering whether Gluster would allow me to share our /home
>partition so whichever host is currently up - it'll have the most
>current /home partition with it. When both are up then both can write
>to it and have the latest version locally.
>
>Can Gluster do this?
>
>I got a hunch that it is possible to just configure some /data/home
>server volume which will be mirrored a-la "Automatic File Replication
>(Mirror) across Two Storage Servers"
>(http://www.gluster.org/docs/index.php/Automatic_File_Replication_(Mirror)_across_Two_Storage_Servers)
>then mount /home on both same machines from that mirrored volume.
>
>Does this make sense or did I get it all wrong?
>
>If not, is there another way to achieve something like this?
>
>Thanks,
>
>--Amos
>
>_______________________________________________
>Gluster-users mailing list
>Gluster-users at gluster.org
>http://zresearch.com/cgi-bin/mailman/listinfo/gluster-users

I think you have it right.
it''s an interesting way to use gluster..  you run a risk on occasion,
however.

if you happen to update files on both ends while they''re 
disconnected, then once you''re re-connected, when you access the same 
file, you can not be sure which version will prevail.

(you can, but it''s difficult to know--as I understand it, gluster 
tracks a timestamp and a revision number--somehow it uses these to 
decide which file is "newer")

Also, gluster doesn''t to automatic healing--meaning, when you 
reconnect it doesn''t immediately push the updates to the other side.. 
this is done only when files are accessed.  So, if you make file 
changes while disconnected, and then reconnect.. change some OTHER 
files, then disconnect again, you may still have an older version of 
the original file

those are my thoughts,
Keith

At 04:14 AM 8/1/2008, Amos Shapira wrote:
>Hello,
>
>I just discovered Gluster a couple of weeks ago and went through the
>initial documentation and got it compiled.
>
>It looks very promising both for my home network and for work.
>
>For now I''m concentrating at home -
>
>We have to Ubuntu 8.04 desktops, one for me and one for my wife.
>
>We generally try to keep them off when not used but at any time any
>one of them could be up or down.
>
>I was wondering whether Gluster would allow me to share our /home
>partition so whichever host is currently up - it''ll have the most
>current /home partition with it. When both are up then both can write
>to it and have the latest version locally.
>
>Can Gluster do this?
>
>I got a hunch that it is possible to just configure some /data/home
>server volume which will be mirrored a-la "Automatic File Replication
>(Mirror) across Two Storage Servers"
>(http://www.gluster.org/docs/index.php/Automatic_File_Replication_(Mirror)_across_Two_Storage_Servers)
>then mount /home on both same machines from that mirrored volume.
>
>Does this make sense or did I get it all wrong?
>
>If not, is there another way to achieve something like this?
>
>Thanks,
>
>--Amos
>
>_______________________________________________
>Gluster-users mailing list
>Gluster-users at gluster.org
>http://zresearch.com/cgi-bin/mailman/listinfo/gluster-users

2008/8/1 Keith Freedman <freedman at
freeformit.com>:
> I think you have it right.
> it's an interesting way to use gluster..  you run a risk on occasion,
> however.
>
> if you happen to update files on both ends while they're disconnected,
then
> once you're re-connected, when you access the same file, you can not be
sure
> which version will prevail.
Yes, I think I'm aware of the general gotachas with multi-node
writers. The mitigating factors in my setup (I hope) are:

1. These are desktop machines which are always connected via a wired
network - so whenever both are turned on they can sync up (i.e. it's
not like one of them is a laptop).
2. Me and my wife use separate accounts so I suppose most of the time
we won't be working on the same files anyway.

I envision it generally that both of us will be able to login to each
of our logins on each machine and just have the files around, while
still allowing me to just upload files from the camera to my desktop
and tell my wife that she can access the photos from hers right away
(and also have a backup in the process).
>
> (you can, but it's difficult to know--as I understand it, gluster
tracks a
> timestamp and a revision number--somehow it uses these to decide which file
> is "newer")
>
> Also, gluster doesn't to automatic healing--meaning, when you reconnect
it
> doesn't immediately push the updates to the other side.. this is done
only
> when files are accessed.  So, if you make file changes while disconnected,
> and then reconnect.. change some OTHER files, then disconnect again, you
may
> still have an older version of the original file
Thanks. That's a point I missed from the little of the docs I read so far.

What's defined as "sufficient access"? Is a stat(2) on the file
enough
to cause the data push or does it actaully have to be open(2)'ed or
does it even actually have to be completely read(2)?

Maybe a simple "find ... -size..." on the shared tree during boot
could trigger a full sync?

Thanks,

--Amos

At 04:09 AM 8/3/2008, Amos Shapira wrote:
>What''s defined as "sufficient access"? Is a stat(2) on
the file enough
>to cause the data push or does it actaully have to be open(2)''ed or
>does it even actually have to be completely read(2)?
>
>Maybe a simple "find ... -size..." on the shared tree during boot
>could trigger a full sync?
http://www.gluster.org/docs/index.php/Understanding_AFR_Translator

look under "Preemptive Self-Heal" for a couple examples.

At 04:09 AM 8/3/2008, Amos Shapira wrote:
>What''s defined as "sufficient access"? Is a stat(2) on
the file enough
>to cause the data push or does it actaully have to be open(2)''ed or
>does it even actually have to be completely read(2)?
>
>Maybe a simple "find ... -size..." on the shared tree during boot
>could trigger a full sync?
http://www.gluster.org/docs/index.php/Understanding_AFR_Translator

look under "Preemptive Self-Heal" for a couple examples.

At 04:09 AM 8/3/2008, Amos Shapira wrote:
>What''s defined as "sufficient access"? Is a stat(2) on
the file enough
>to cause the data push or does it actaully have to be open(2)''ed or
>does it even actually have to be completely read(2)?
>
>Maybe a simple "find ... -size..." on the shared tree during boot
>could trigger a full sync?
http://www.gluster.org/docs/index.php/Understanding_AFR_Translator

look under "Preemptive Self-Heal" for a couple examples.