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 Clustering 101
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mohdowais
Sheikh of Yak Knowledge

United Arab Emirates
1456 Posts

Posted - 10/14/2003 :  09:20:33  Show Profile  Visit mohdowais's Homepage  Reply with Quote
Hi all:

We are planning to get ourselves a brand new set of hardware for our web application:
2x compaq servers (2.8Ghz 1GB RAM)
5x 18GB 15k SCSI RAID-5

Now we plan to set up clustering between the two with one active and one passive node. The active node will run both IIS and SQL Server. But I was thinking, why should the other beefy server lay around waiting for it to fail? Could we set up clustering such that both nodes are active, one node handles IIS, the other handles SQL Server. And if the Web Server fails, the SQL Server machine automatically takes up both jobs. And vice versa.

I've read a *lot* about clustering in the past few days, I've even read about Active/Active setups (but both servers are handling only IIS), but nowhere does it address such a scenario. It seems to me that this should be a fairly common scenario...

Anyway, is this possible?

Owais


Make it idiot proof and someone will make a better idiot

tkizer
Almighty SQL Goddess

USA
37133 Posts

Posted - 10/14/2003 :  12:16:11  Show Profile  Visit tkizer's Homepage  Reply with Quote
quote:
Originally posted by mohdowais


The active node will run both IIS and SQL Server.



Eeks! Why oh why would you do this? SQL Server should be on a dedicated box.

quote:
Originally posted by mohdowais


But I was thinking, why should the other beefy server lay around waiting for it to fail? Could we set up clustering such that both nodes are active, one node handles IIS, the other handles SQL Server. And if the Web Server fails, the SQL Server machine automatically takes up both jobs. And vice versa.

I've read a *lot* about clustering in the past few days, I've even read about Active/Active setups (but both servers are handling only IIS), but nowhere does it address such a scenario. It seems to me that this should be a fairly common scenario...

Anyway, is this possible?



I would not recommend doing this. For environments that have a passive node, the passive node is used for SQL Server to fail over to.

We run active/active in our environment. Each is running a couple of instances of SQL Server.

I would suggest, if money allows, to have a separate cluster setup for IIS. It is just not recommended to run IIS and SQL Server on the same box. IIS will suffer due to SQL Server using up so much memory.

Tara
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MichaelP
Jedi Yak

USA
2489 Posts

Posted - 10/14/2003 :  12:45:30  Show Profile  Visit MichaelP's Homepage  Reply with Quote
If the box is running IIS (or another node in the same cluster is running IIS) then the outside world can hit your SQL server, and that's generally a no-no. I highly suggest getting two (or more) webservers, use Network Load balancing (NLB) with them and use Active/Passive or Active/Active clustering with SQL Server. We do something like that here and it works great. We use a Cisco hardware device instead of NLB.

Michael

<Yoda>Use the Search page you must. Find the answer you will.</Yoda>
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MichaelP
Jedi Yak

USA
2489 Posts

Posted - 10/14/2003 :  12:47:34  Show Profile  Visit MichaelP's Homepage  Reply with Quote
Also, RAID 5 might not be the optimal way to configure your array. Don't forget you need a quorum drive with Microsoft Clustering.

Michael

<Yoda>Use the Search page you must. Find the answer you will.</Yoda>
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MichaelP
Jedi Yak

USA
2489 Posts

Posted - 10/14/2003 :  12:49:52  Show Profile  Visit MichaelP's Homepage  Reply with Quote
Oh, one more thing. You might want to consider looking into the HP/Compaq MSA1000. It's a shared storage box that works with clustering. They are giving away like (10) 73GB drives with it right now, but I think that ends at the end of the month. It's SCSI drives, but it attaches to your Servers via fibre channel.

Michael

<Yoda>Use the Search page you must. Find the answer you will.</Yoda>
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Merkin
Funky Drop Bear Fearing SQL Dude!

Australia
4970 Posts

Posted - 10/14/2003 :  22:46:49  Show Profile  Visit Merkin's Homepage  Reply with Quote
I agree with Tara. You are entering a world of pain if you do something like this.
IIS and SQL Server clustering are totally different beasts, with totally different methods.

Keep your database boxes specifically for that purpose. Then get some lower cost boxes for your web servers. Your web cluster can be set up in a load balanced configuration using round robin DNS (or similar) which makes adding new web server nodes really simple, and you will get a higher throughput for web traffic. SQL Server clustering is totally different to that.


Damian
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mohdowais
Sheikh of Yak Knowledge

United Arab Emirates
1456 Posts

Posted - 10/15/2003 :  01:10:09  Show Profile  Visit mohdowais's Homepage  Reply with Quote
Excellent suggestions, folks, thank you!

I'm now beginning to see (and understand) the issues, but there is still one thing that confuses me. You say that I shouldn't run IIS and SQL Server on the same machine. I'll make sure that doesn't happen, and that's what I was trying to avoid by getting one machine to run IIS and the other to run SQL Server, but only in the case of a failover, the still-standing server will take over both the tasks (hopefully only for a short while). Or am I completely wrong here, because both the services are running on the same virtual server?

We don't really have a lot of traffic, but redundancy is very important.

Michael: I guess I haven't considered where the quorum drive is setup...I just need to have it on its own volume, right? I read most of the posts on SQLTeam dealing with RAID and many people suggested RAID 10 if you can afford it, plus a RAID 1 array for the Transaction logs. But I think the cost is getting out of hand Unfortunately, most pre-packaged clustered solutions from Compaq are available only in North America, it's quite a bargain.

Owais




Make it idiot proof and someone will make a better idiot
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Merkin
Funky Drop Bear Fearing SQL Dude!

Australia
4970 Posts

Posted - 10/15/2003 :  01:18:14  Show Profile  Visit Merkin's Homepage  Reply with Quote
You want the Quorum drive to be in an external drive array. This is plugged into a fibre channel hub connected to all machines in the cluster. You are correct in assuming this isn't cheap


Damian
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mohdowais
Sheikh of Yak Knowledge

United Arab Emirates
1456 Posts

Posted - 10/15/2003 :  01:40:17  Show Profile  Visit mohdowais's Homepage  Reply with Quote
Thanks Damian. So since I have 5 disks in my array, and one disk is taken up by the Quorum, one is taken up by the parity drive, that leaves me with 3 to store stuff on. Duh?

Owais


Make it idiot proof and someone will make a better idiot
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Merkin
Funky Drop Bear Fearing SQL Dude!

Australia
4970 Posts

Posted - 10/15/2003 :  01:46:09  Show Profile  Visit Merkin's Homepage  Reply with Quote
Here are some helpful links :

http://www.microsoft.com/technet/treeview/default.asp?url=/technet/prodtechnol/sql/reskit/sql2000/part4/c1261.asp

http://support.microsoft.com/default.aspx?scid=kb;EN-US;254321

http://support.microsoft.com/default.aspx?scid=KB;en-us;q259267


Plus a bunch of articles on www.sql-server-performance.com



Damian

Edited by - Merkin on 10/15/2003 01:47:51
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chadmat
The Chadinator

USA
1974 Posts

Posted - 10/15/2003 :  14:53:02  Show Profile  Visit chadmat's Homepage  Reply with Quote
quote:
Originally posted by mohdowais

Thanks Damian. So since I have 5 disks in my array, and one disk is taken up by the Quorum, one is taken up by the parity drive, that leaves me with 3 to store stuff on. Duh?

Owais


Make it idiot proof and someone will make a better idiot



You should mirror your Qurom drive as well. It doesn't take much space, but if something happens to the Quorom, the whole cluser is ...Wait for it... Cluster F*@#ed.

-Chad

http://www.clrsoft.com

Software built for the Common Language Runtime.
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MichaelP
Jedi Yak

USA
2489 Posts

Posted - 10/15/2003 :  18:22:02  Show Profile  Visit MichaelP's Homepage  Reply with Quote
Chad is totally right. We've got two 9GB Drives Mirrored JUST for the Qurom drive. We use like maybe 500Mb's of space, but MS reccomends not putting anything else on that drive.

Yeah, clustering in general is not cheap at all. A Load balanced cluster of two or more webservers is cheap and easy to setup(MS network load balancing, Round Robin DNS). A failover cluster for SQL server is not cheap to setup.

As far as hardware, you might want to check Ebay. You can usually get everything to need to build up a light weight cluster on there for pretty cheap.

Michael

<Yoda>Use the Search page you must. Find the answer you will.</Yoda>
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Merkin
Funky Drop Bear Fearing SQL Dude!

Australia
4970 Posts

Posted - 10/15/2003 :  19:15:01  Show Profile  Visit Merkin's Homepage  Reply with Quote
ROFL Chad.
Is that the official term ?


Damian
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mohdowais
Sheikh of Yak Knowledge

United Arab Emirates
1456 Posts

Posted - 10/16/2003 :  01:09:04  Show Profile  Visit mohdowais's Homepage  Reply with Quote
AAAAAAHHHHHH!! You people have managed to scare me now!

Can I mirror just one drive on a RAID 5? I'll up the requirements to 7 disks then.

Still curious, can you cluster IIS without using NLB?

Thanx

Owais


Make it idiot proof and someone will make a better idiot

Edited by - mohdowais on 10/16/2003 01:09:53
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Merkin
Funky Drop Bear Fearing SQL Dude!

Australia
4970 Posts

Posted - 10/16/2003 :  01:26:27  Show Profile  Visit Merkin's Homepage  Reply with Quote
If you just want to mirror you don't need RAID5. You can just use RAID0 (or is it 1, I can never remember).

quote:

Still curious, can you cluster IIS without using NLB



You could I guess, but I don't see any point.

Damian
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mohdowais
Sheikh of Yak Knowledge

United Arab Emirates
1456 Posts

Posted - 10/16/2003 :  03:34:28  Show Profile  Visit mohdowais's Homepage  Reply with Quote
RAID level 0 is Disk striping (no redundancy)
level 1 is mirroring (requires twice the number of disks)
5 is striping + parity (good in-between solution)
5+1 is striping + parity + mirroring (needs more disks)

Implementing 5+1 for the entire array requires a lot of disks, that's why I wanted to know if I could mirror only the quorum drive. As far as my understanding goes, I cant have two levels of RAID on a single array.

Owais


Make it idiot proof and someone will make a better idiot
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MichaelP
Jedi Yak

USA
2489 Posts

Posted - 10/16/2003 :  11:56:14  Show Profile  Visit MichaelP's Homepage  Reply with Quote
Yeah we have one array with two drives RAID 1 for Qurom. We also have other arrays setup to store our data. The minimum number of drives you need is 5 drives.
2 for Qurum
3 for RAID 5

Needless to say, you'll not have much space in this setup, so you'll probably want more drives in your RAID 5 array. Also, RAID 5 isn't the best for write heavy databases.

Can IIS be clustered using MSCS? I'm not sure.

Michael


<Yoda>Use the Search page you must. Find the answer you will.</Yoda>
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