June 26, 2007 at 8:00 am
On my SQL 2000 box, I currently have two RAID arrays one is a Mirror which contains the OS and the other is a RAID5 (which I have just learned is bad for SQL) which contains the SQL installation and databses.
Due to my capacity running out on my RAID5 I need to upgrade the hard drvies in this array. There are four drives in this array currently 3 in the RAID and 1 as a hot spare. I plan on changing these four drives to larger capacity and change the array to a 1+0.
My question is this, can I back up all of the data on this array. Blow away the old one and create the new array and then restore the data without having to relaod any software or worry about problems with SQL still functioning properly. Since the OS and registry are on the other array which will not be touched would doing this cause any problems? Is there a better way to do what I am trying to accomplish?
June 26, 2007 at 7:57 pm
Is it just data and logs on the R5 array? If so, you should be fine. You'll need to be sure the drive letters are the same.
BTW, as a thought, I've heard multiple R1 arrays is better than a R10 one. Not sure it matters, especially if you only have 4 drives.
June 27, 2007 at 6:21 am
Yes it is basically just data and log files, the database apps were installed to but being that the OS and registry info which contains the info needed to direct everything to that partition and folder set I did not see it as a problem but was curious to know if others have had to do this and would it work without any issues.
Thanks for the info and reply.
July 24, 2007 at 7:05 am
So being that SQL is installed on this array as well as another application which has a databse attached to SQL should not cause any problems? So long as the drive letter and folder structure at the point of restore remain the same there should not be any problems. To clarify my exisitng set up
Server
RAID 1
OS
Registry
Misc Apps
RAID 5
SQL Installation
SQL Databases
Transaction Log Files
Other Apps
Also I was doing more research and read that before doing any of this I should detach the databases the do my backup then restore data then reattach databses. Is this correct?
July 24, 2007 at 9:02 am
You should be ok backing up the disk then restoring them. Howerver, make sure all services are shut down and disabled before you start doing this.
Wouldn't hurt to make sure you have a good backup of the databases before you start of course!
July 24, 2007 at 10:31 pm
Robert -
Is replacement of your RAID 5 with new drives your only option? How about adding additional drives/channels either internal or external to the server?
Between the cost of "big" drives (e.g. a 300GB drive costs about twice as much as a 146GB these days), time/cost to perform to upgrade (e.g. backup restore, etc.) you may want to see if you can justify adding an external array?
If you have to go forward with the in place upgrade be sure that your backup of the array before you tear it up includes NTFS permissions and that your restore includes same.
Joe
July 25, 2007 at 6:24 am
Hi Robert.
Raid 5 is not bad for SQL. It is a poor choice for SQL if the system requires more disk performance than your Raid 5 array can deliver.
July 25, 2007 at 2:10 pm
ok Jeff - hard question for you. How do you determine the disk performance you require vs what the RAID 5 can deliver?
July 26, 2007 at 6:50 am
Alrighty then, good question.
It depends. Usually, business requirements will dictate the level of performance needed. They also have a say in budgeting, which can sometimes makes the choice easy.
For X, you will get Y. On one of the SANs that I use, I know that a 14 drive array will get me 26MB/s sustained write (with a SQL page-sized IO) if I use Raid 5, and 120 MB/s if I use Raid 1+0. I know this because I tested it using IOMeter. (Check it out)
Now I would almost never design a SQL server with the intention of putting the data and log files on Raid 5, but there are cases where it wouldn't hurt to do so. I support a very small installation of Dynamics GP. The database is tiny, and one admin assistant makes 3 or 4 entries a day, and spits out 4 invoices at the end of the month.
I don't want to put this database on the production cluster, because I want to maximize the performance there, and I don't want any other unknown cross-affection, so it goes on its own box. That happens to be a 1U server with 3 drive bays because that's the choice I was given. It's set up on a Raid 5 and that's the end of that story.
Generally, if I can be certain that a particular application will exhibit no performance benefit from an increase in disk performance, I would consider all of the storage options. However, I'm usually asked to make things as fast as possible. I like it that way.
July 26, 2007 at 1:09 pm
I would also put my plug in for the speed of the disks. Raid 1 with 10K disks might be slower than raid 5 with 15K. (assuming your controller can keep up with the disks!). We have 3 tiers of SAN storage 15K, 10K and 7200 SATA. Stuff on the 15K is substantially faster than the 10K.
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