MSSQL High Aviabalability questions?

We are using MS SQL 2008 with R2 in Windows 2008 server

1). I am planing to implement HA to my company. I know in MS SQL, we can do mirroring, log shipping and replication. Can someone tell me what is the difference among them? What advantages and disadvantages for them?

2). Can we do replication for system database? what is the per-requsite for doing transaction replication?

3). After the log shipping is done, can we create tables or add field to table in standby server. Do it cause the log shipping job down if I do so?

4). What mode should I use when doing log shipping?
wasabi3689Asked:
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Anthony PerkinsCommented:
Can we do a replication for a table without any key set and index?
No.  The table requires a Primary Key.
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momi_sabagCommented:
you need to be more specific with your requirements
by ha you mean:
1) you want an additonal stand by instance you will be able to fall back to when the main instance fails
2) you want to add more instances to spraed the work load since a single instance can't handle all the work
3) where would the different nodes be physically (same lan, same san etc...)
4) how much latency between the nodes can you efford if any at all?
5) how fast should the switching between them be?
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Ramesh Babu VavillaCommented:
1).it depends upon on your requirement , if you want aotomatic failover , you can user Mirroring,
manual Log shiping is good.
2). Can we do replication for system database? what is the per-requsite for doing transaction replication?
no we cant do replication for system databases,
pre requist
1_ both the db should be in FUll recovery mode, suggested to be
2) good power full NIC cards
3) plan how you RAID are perofrming.

3). After the log shipping is done, can we create tables or add field to table in standby server. Do it cause the log shipping job down if I do so?
asolutely no
as the databases are in the standby(readonly) and no recovery mode, additions are not allowed

4). What mode should I use when doing log shipping?

Full recovery mode
and both the Servers principle and standy should be started with the same user account,
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wasabi3689Author Commented:
One more question about replication.

Can we do a replication for a table without any key set and index?
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Ramesh Babu VavillaCommented:
no we cant to transactin replciation, withour a primary key in
.

we can do merge replication for   that
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