vg00

[Global Server Operation]

I'm setting up a new rp7410 as a database server which has three internal disks each having 36 Gig of space. I plan to use two (one for primary and the other as a mirror of the primary), and the third one as an alternate boot. The database admin is requesting that /oracle and other applications be installed on the internal disk which will belong to vg00? I'm concerned that this will cause some performance problems? I'm suggesting that these be installed on the EMC. However I'm thinking about at least allowing /oracle to be on the internal disk. Any advice?

[Michael Tully · Accepted solution]

Don't allow this. There is enough read activity from the internal disks already. You'll get far better read/write performance from an external disk array, as these units carry their own internal caching. Internal disks must rely on the system itself to provide it's caching.

[S.K. Chan]

We have been setting up our servers in such a way that only the root VG resides on the internal disks. Having data or application on vg00 is definately not the way to go. Performance is one thing, crash recovery is another. You should stick with having 2 disks (mirrored vg00) and the other as "alternate boot", that's it. From personl experience, we have had too many cases of non-root stuff sitting on vg00 which eventually have to be moved off to an external devices and all of a sudden the users keep asking .. "did you guys just upgraded the server ? .. how come it's so fast now ."

[Global Server Operation]

Thanks. I just wanted to confirm. I want to make sure I set this system up right the first time. Thanks you.
I will set up the following filesystems. Any suggestions?

/ 304MB
/stand 200MB
/home 20MB
/opt 2GB
/tmp 1GB
/usr 2GB
/var 2GB or 4GB
Swap 16 GB
Oracle requires swap to be at least twice the size of memory.

[Global Server Operation]

Thanks S.K.Chan for confirming what I was thinking. It helps to post it out there to see if I'm on the right track.

[S.K. Chan]

The FS sizing looks good. There isn't any hard rules of what the initial sizes should be. In your case it's sufficient. What is more important is .. down the road if you need to inrease these FS space, can you afford a downtime window from you users ? If the answer is no, you might want to seriously consider purchasing OnlineJFS so that you can increase the vxfs FS on-the-fly (without needing to down the server).

[Michael Tully]

You can be a little conservative with the swap being on the internal disks. Try to spread it out. It is best not to have all of it on the same disk anyway.
In my opinion I would place the majority of the swap on the external disk. You don't need to place all your swap in /dev/vg00

[Global Server Operation]

Thanks Mike. I plan to put half of the swap on the internal and the other half on the external.

[S.K. Chan]

Sorry .. I do want to mention one more point (echoing Michael's suggestion on swap), yes, I totally agree with Michael. You can do something like having 8GB primary swap on vg00 and another 8GB secondary swap on any non-vg00, both should be setup with the same priority for interleaving. If I were you I would break it up into 4GB "chunk".

[Patrick Wallek]

16GB is WAY too much swap. There is no way I'd configure that much swap on a system. I hate to say it, but Oracle about 5-10 years behind with that swap requirement.

Why do they require that much swap? Are they planning on using it? I hope not, especially if you have 8GB of RAM. I'd invest in more RAM before I'd put that much swap space on a system.

By the way I just bought a 2GB RAM kit for an L and it was a little over $500 US. RAM is CHEAP!!!!!

[Global Server Operation]

From what I'm hearing from the Oracle DBA, Oracle will not install unless you have at least swap size at least twice the size of memory.

[S.K. Chan]

I'm not a DBA person but I can tell you it's correct, you need loads of memory+swap for Oracle installation simply because the Oracle installer program needs it. What I've done before is .. before the installation, we create a "temporary" filesystem swap just to fullfil the installation requirement. After the installation, the FS swap is deleted. That way I keep the "correct" device swap size which does not include the swap requirement for Oracle installation.

[Bill Hassell]

I'll second the TEMPORARY need for lots of swap to install (not run) Oracle. SAP is even worse. Installation may need 3xRAM or more to install, yet neither Oracle or SAP need that massive swap space after installing. You can return the extra swap space after installation is complete.

[Global Server Operation]

What is the difference if Oracle is installed under /oracle on the root disk verses oracle being installed under /usr on the root disk? The dba stated that the Oracle application is pretty static.

[Global Server Operation]

As far as Oracle having it's own files system on the root disk, it was suggested by unix admin that I could do the following:

create /oracle on the mirrored disk and then mirror it back to the primary disk?
Any suggestions?

[Patrick Wallek]

I still wouldn't allow it. You are always going to have people executing sqlplus and other stuff from $ORACLE_HOME/bin and you don't want that extra overhead on your root disks.

Make a /oracle or a /usr/oracle on your EMC and install it there.

KEEP VG00 FOR OS STUFF ONLY!

[Patrick Wallek]

Create on the mirror first, then mirror to primary boot? That's supposed to make a difference in performance? I don't think so!

Do NOT allow ORACLE to be installed on your OS disks. No matter what!!!!!!

[John Poff]

Hi,

I agree with Patrick. We run lots of Oracle databases here, and we always put the Oracle home on a filesystem on our EMC array. I've watched the disk I/O by filesystem many times in Glance, and the Oracle home gets lots of disk traffic. Your DBAs will get better performance if their Oracle home is on your EMC array. Besides, if your system crashes or if you decide to completely upgrade to a new system in the future, all you have to do is build the box with the OS installed, hook up to your disk array, vgimport your volume groups and off you go. Having the Oracle home on your vg00 volume group means you have to take all that with you. Plus, if you use Ignite to do your OS backups, you'll have to backup /oracle and keep that with you. You'll have the extra overhead of backing it up in Ignite, and you'll also have the overhead of restoring it when you do a recovery.

Listen to Patrick. Convince your DBAs to put their Oracle home on the EMC array.

JP

[John Payne_2]

Oracle definitely does not need the swap. Consider turning the parameter swap_mem_on to 1. (Turning it on.) This will make a pseudo-swap space. Oracle should install with the 'imaginary' swap space. Our DBA's used to whine about not having enough swap, until I asked them to show me a single instance of using the swap space. They couldn't, oracle installed, it works great.

Hope it helps

John

[Global Server Operation]

Everyone, thanks for all the good responses. I will provide this to the DBA.