August 13, 2007 at 3:34 pm
I have a server running four instances of SQL Server 2000 on top of Win2k3 that has four drives in a RAID-5 config on one SCSI controller, the box has only two slots available for additional drives. It's about to be upgraded to SQL 2000 Enterprise. The server has no other duties beyond SQL Server.
This server is going to be getting four more instances added to it soon (I'm shutting down a shaky 2xP3/500 server), it'll probably have seven or eight instances when all is done. It currently has 4gig of ram in it, I'm hoping to get another 4gig in it before I do the migration.
I'm a little concerned about this configuration, I don't like having everything on one RAID partition (and on only two drive letters at that!), but it was configured that way when I started here and I'm stuck with it for the moment. I'm particularly concerned that I'll have a minimum of seven instances hitting tempdbs. There's plenty of disk space available now, and the transfer will only eat another 10-15 gig, so it won't be a problem afterwards. At least none of the instances are exceptionally high transaction volume, I'd be surprised if any of them are doing more than a dozen transactions a minute (note to self -- set up PerfMon for transaction count and tempdb usage).
Here's my option. I can probably get two more drives installed for a total of six. I am considering three mirrored pairs: C: for OS & SQL, D: for databases & tempdb, E: for transaction logs and backups. I stagger my backups to reduce disk contention, so I'm comfortable with a design like this that puts my initial backups on my log drive since my tran log backups are pretty small.
Another option would be to go RAID 0+1 or 10. Or I could leave it alone and add two more drives to the array so at least I'd have everything spread across more spindles. It looks like the controller card doesn't support hot spares, so unfortunately I cannot add one drive to the array for add'l space and one drive for a hot spare.
Suggestions? Expand my RAID-5 and leave well enough alone or go 0+1 or 10?
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[font="Arial"]Knowledge is of two kinds. We know a subject ourselves or we know where we can find information upon it. --Samuel Johnson[/font]
August 18, 2007 at 6:13 am
you realise sql2k goes out of support next year? 8 instances on 8gb ram means you can only allocate 750mb to each instance unless you want anachy and the chance of any one instance bringing down the others?
Disks? I can't see any reason anyone would want to use raid 5 and I'd probably put all the disks into raid10 and carve. Whichever way you go I think you're between a rock and a hard place!
with 6 disks I might be tempted to go a raid 1 for o/s and binaries and 4 disks in raid 10 for the data files and logs. logic says you should seperate logs but if you haven't got high throughput then it won't be so much an issue.
[font="Comic Sans MS"]The GrumpyOldDBA[/font]
www.grumpyolddba.co.uk
http://sqlblogcasts.com/blogs/grumpyolddba/
August 20, 2007 at 8:32 am
Yeah, I'm aware of 2000 going out of support. The box that I'm migrating from is kinda shaky, so the migration is going to happen. Plus, it'll free up space from my rack cabinet. Probably next June/July we'll be able to start upgrading to 2008, I'm hoping to get 2005 on a test server in a couple of months.
Basically I am already between a rock and a hard place. I don't like having eight instances on a single box, but I don't have any other servers right now. We have a policy of pretty much having to have one instance per database app because they're mostly third-party apps, and if the vendor needs to remote in to work on it, we don't want them seeing anything else. By limiting them to one instance, we have that. (Yes, I'm confident that proper security permissions are more than adequate to the task and would let us have all the databases in one instance, but I'm not the boss.)
The way I see it, I don't think that we can get away from reformatting the server and reinstalling it from scratch. Had I been working here when they installed it, I would have fought tooth and nail against RAID-5, but what's done is done. I'm still undecided between RAID-0/1 and 1/0, I really ought to look at the drive manufacture lots of the current drives before I decide the new mix.
Unfortunately I'm kind of stuck in that the cabinet is only good for six drives, and adding an expansion cabinet might not be viable.
The only good thing is that all eight DBs are pretty low transaction volume. I've spent some time monitoring them and one does very rare bursts where it'll hit over 100 transactions per second, but it only does that every few minutes and it's only for a single monitoring spike.
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[font="Arial"]Knowledge is of two kinds. We know a subject ourselves or we know where we can find information upon it. --Samuel Johnson[/font]
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