[THIN] Re: SQL Replication possible long term problems?
- From: "Ron Oglesby" <roglesby@xxxxxxxxxxxx>
- To: <thin@xxxxxxxxxxxxx>
- Date: Tue, 21 Jan 2003 10:33:46 -0600
We had it setup in a lab using Merge replication, which seemed just fine
but is un supported. We are now changing it to transactional replication
with that two phase commit setup for updating. We have not tested this
yet completely yet to say yea or nay to it.
Anyway by there directions in the Advanced concepts guide for FR2 this
is the type of replication you want (also they are missing a step to
configure the subscribers properly after setting up the distributor,
hopefully I will have it all documented this week).
I will let you know what our testing reveals but Merge did seem to work.
Ron Oglesby
Senior Technical Architect
=20
RapidApp
Office 312.372.7188
Mobile 312.961.2380
email roglesby@xxxxxxxxxxxx
=20
-----Original Message-----
From: Andrew Knight [mailto:andrew@xxxxxxxx]=20
Sent: Tuesday, January 21, 2003 10:18 AM
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: SQL Replication possible long term problems?
Ron,
Have you been able to get replication to work as per Citrix
instructions.=3D
=3D20 We tried it some time ago and ran into read/only problems. After
dis=3D
cussing with European Tech Support who backed it off to Florida, they
res=3D
ponded with a very non-committal approach. In the end we had to use
scri=3D
pting to get it to work correctly.
Regards,
Andrew
-----Original Message-----
From: Ron Oglesby [mailto:roglesby@xxxxxxxxxxxx]
Sent: 21 January 2003 14:34
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: SQL Replication possible long term problems?
OK. Well it seems here is what goes on.
The "read only" stance by Citrix is not that at all. You can use
transactional replication but the Citrix servers that are configured for
that secondary DB will update the primary DB (although I wouldn't do it
with something big like a MF install).
Anyway they recommend using the two-phase commit for the transactions.
In other words the remote "read-only" DB will take the request from the
Client MF server. Then instead of updating its DB it will pass the
request up to the primary distributed database (the master) the master
will make the change and all the replicas will receive it.
So the initial comments of the remote machines not able to update (or
having to update) the data store was incorrect. They have even outlined
this and now recommend it in the advanced concepts guide(but they never
mention what the check box does).
Anyway for any of you that want to know, here ya go.,
Ron Oglesby
Senior Technical Architect
=3D3D20
RapidApp
Office 312.372.7188
Mobile 312.961.2380
email roglesby@xxxxxxxxxxxx
=3D3D20
-----Original Message-----
From: Ron Oglesby=3D3D20
Sent: Monday, January 20, 2003 9:01 AM
To: thin@xxxxxxxxxxxxx
Subject: [THIN] SQL Replication possible long term problems?
Ok. I have been working with a client on their XP migration. Hundreds of
Servers across 4 data centers. We were going to use SQL 2k with Merge
replication for the data stores. This worked great in a lab and seemed
stabile as could be. Anyway Citrix told us that they wont support Merge
replication only transitive (one-way, master -slave) replication. SO in
thinking about this design change I started thinking about possible
problems with this in a large env with lots of remote servers.
I mean think about the simple things like the way the server will update
the data store if a print driver (or anything else) is installed.
Lets say that a driver is updated on a remote citrix server that talks
to the DataStore via one of the read-only replicas. This driver update
can be through Citrix replication, or via a script that updates them
remotely.
Anyway a new driver is installed on the server, the IMA service attempts
to update the DS once it "sees" the new driver on the OS. Since the
DataStore that this server is talking to is read only what
happens?=3D3D3D2=3D
0
My guess is that it will attempt to write this info to the DS (which
will fail or be over written by the next replication) and since it can
not write this info will it continue to try and write that info? What
happens when I have 50 or 100 remote servers all failing to write this
type of info.? What will be the effect on server performance and data
store performance. Changing all the servers to talk to the master/
writeable DS just to add a print driver or hotfix would be a pain.
=3D3D3D20
Obviously this will also be a problem with things like Services packs,
MS hotfixes, Citrix hotfixes, IP changes, etc. So every time anything is
updated that writes to the DS we have to run a dsmaint, change the DSN
so the server talks to the writeabile DS, restart the IMA service, do
the update, then change it back then restart the IMA service again. =
=3D3D
=3D3D3D20
Anyone else dealing with this? Or have any thought on long term
ramifications of this inherently "weak" design?
Ron Oglesby
Senior Technical Architect
=3D3D3D20
RapidApp
Office 312.372.7188
Mobile 312.961.2380
email roglesby@xxxxxxxxxxxx
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