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RAID 5 configuration for SQL SERVER
Hi all, recently company has decided to upgrade database server hardware. Currently, the way it is designed is that database is configured to be on RAID 5. log file and the data files are on raid 5. RAID 5 has around 3 disks of 750 gb and the spindle speed of 7200 rpm. upgrade is only in the sense of RAM. but not the purchase w.r.t RAID. I need to make best of the situation and come up with best solution. as per the application and database is concerned, it is a more read extensive application, than write as per day to day activity is concerned. my Research says that raid 1 and raid 10 are the best for Logs and the data files respectively and the choice of raid 5 is not optimal for sql server. But the choice had been already made. i spoke to my network admin and he said he could segment the raid drive, so that there could be some separation. all the database,OS(Windows server 2008), database logs all exist on raid 5. i am not sure and aware of the complete concept of raid. what would experts suggest?
I have run systems with the data files on RAID 5 and it has performed acceptably. If you are building new and have 100% control it isnt THE ABSOLUTE FASTEST but it does offer data security if a drive fails. Splitting (partitioning) the RAID5 wont give you any performance advantage, you will still have the same spindles even though the OS will see more than one drive. If you have another array (or single disk) then providing there is space I would suggest putting the log files on that and the data files on the RAID5, just to split log and data access. If the system is that vital then the business will have to decide that the cost and effort of reconfiguring the drives is worth the performance improvement that would be brought about. I think you will have to make the best of what you have and see how it goes
+1 : yup not the best, but if forced to use RAID5 then you can make it work. Good point about partitioning over the same spindles, so many times have I had the argument with people about them having multiple disks, and I've had t say 'no - you've got multiple **drives**, not disks'
The only place I agree with the partitioning is to keep the "C:" drive with its user folders (Documents & Settings, etc.) from being able to grow and consume disk space - yet another reason to preallocate database files :) But yeah, spindles are the key to throughput and with only three the OP is limited. At least in this configuration a single drive failure is recoverable.
If disk does start to become a bottleneck, then you've got the option in the future to rebuild away from RAID5. Better to start now than when you've got a live server, but if the decision is out of your hands, then make sure your concerns are noted.
As you already know, the raid 5 isn't the best solution, and log files, data files and tempdb should be separated from each other. If you can't convince them to invest in more hardware, make sure you measure the performance and pay attention to page_io_latch waits, io stalls etc
