[Samba] One shared folder to be HA over CIFS to windows clients

[Daniel Müller]

First approach: drbd in master master mode having two server shares
everytime synced.
Or (glusterd) glusterfs 3.1 having 1 to ....xxxx servers synced in
realtime
To setup simple failover with samba and drbd look here for  a hint
:[Samba] HOWTO samba4 centos5.5 named dnsupdate drbd simple failover

Good Luck 
daniel

On Sat, 8 Jan 2011 12:05:23 +0800, David Roid <dataroid at gmail.com> wrote:
> I think what you really need is clusterd file system..
> 
> 2011/1/8 Emiliano Bonassi <benazhack at gmail.com>
> 
>> Hi,
>> i'm Emiliano this is my first mail to samba mailing list.
>> I have to solve this issue for a company. They need to had a folder,
>> shared
>> over CIFS for windows/mac clients, that is always available, also if
the
>> server who host it hang up or burn.
>> I've looked for a lot of solution but i cannot find the right for me.
>> Actually the company has two server, all running debian lenny as linux
>> distro.
>> The first one, a quad core proliant ml350 g5 6tb raid 10, work as
primary
>> server. On it i've installed vmware server that runs a win2003 r2 guest
>> for
>> central authentication,domain policing ecc. It has another role : the
>> primary file server, running  a samba server integrated with AD.
>> The seconde one, a pentium 4 1,2 tb raid 5, work as secondary server.
>> Like
>> the proliant it has vmware server running a BDC w2k3 r2 for fail-over
and
>> load balancing windows services. Here the file sharing is offered again
>> by
>> a
>> samba server that shares archive folders.
>> Now, how can i have the same shared folder on both file servers?
>> I can adopt microsoft technology : use DFS filesystem and FSR replicas.
>> Actually, i'm fallen in love with the DFS functionality that permit to
>> uniform the namespace of file servers resource using only the name of
the
>> ad
>> domain, but i hate the limits of FSR replicas.
>> Hyp:
>> - Think that i use DFS and setup that \mydomain\dfs\aaa refer to
>> \firstserver\aaa and \secondserver\aaa.
>> - aaa on the firstserver and on the secondserver are the same
>> - i've setup FSR replicas continuosly between the two shares.
>>
>> Now, if from one my win client i poll for \mydomain\dfs\aaa , using
>> somekind
>> of roundrobin\casual algorithm, the DC tell me that \mydomain\dfs\aaa
is
>> \firstserver\aaa or \secondserver\aaa.
>> Suppose, that DC translate the dfs share with the share on the second
>> file
>> server, this means that if i open a file gino.txt i'm working on
gino.txt
>> on
>> secondserver.
>> So now, before the FSR replica, second server got a version of gino.txt
>> newer than first server.
>> Now there is a little window of time when if another client ask for the
>> same
>> dfs share and the same file, it could be possible that DC translate
>> \mydomain\dfs\aaa with \firstserver\dfs\aaa and this second windows
>> client
>> works a different version of the file.
>> Now imagine, that, always before the start of FSR replica, this second
>> windows client save a modified version of gino.txt .


>> The FSR algorithm take a decision, "i propagate the newer version of
>> file".
>> So DFS doesn't work for my situation, i think.
>>
>> So i ask to you if CTDB samba could work for my problem.
>> I think no, because i have to have the same configuration (also shares,
>> here
>> is the problem, i need only one share) between the two fileservers.
>> I'm trying to test this configuration: using LVM create a LV and mirror
>> with
>> drbd between two fileserver.
>> After, put a GFS2 filesystem on them and sharing the filesystem as two
>> separate shares on the two file servers.
>> Now i think that DFS could work as a peacemaker to decide which host is
>> up
>> and translate DFS correctly.
>> Suppose that i open gino.txt on \1st\aaa , modify it, and save it. If i
>> setup drbd with the sync mode, instantanously, because the copy it's at
>> the
>> block level, i have the same file on \2nd\aaa.
>> But if i open gino.txt on \1st\aaa and gino.txt \2nd\aaa , who tell to
>> the
>> two usesr that the same file is opened on both fileserver?
>> From my test seems that only ctdb samba could provide a locking
>> mechanism (
>> at the cifs level), but gfs2 doesn't provide nothing like that.
>>
>> My hope is that someone had the same issue and solved in some way, i
know
>> that it is long but it's also difficult to explain my doubts and
>> willings.
>> Thanks for the reply,
>>  Emiliano
>>
>>
>> PS: I've looked for also GlusterFS but not tested, i'm scared that
>> operating
>> as FUSE there will be some performance break down. I will test, i wish.
>> --
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