June 20, 2008 at 12:21 am
Hello Guys!
I have database requirements of high reads and joins of different tables. I have only three disks (physical) available. So, would it give better performance by putting it in RAID5 and put all the file groups on one LOGICAL disk
OR
would it be better to get it out of RAID, make three logical drives, put different partitions on different filegroups, residing on different logical drives.
Which one would be better ???
June 20, 2008 at 12:34 am
Depends on how much space you need, I would probably Install everything on one disk and raid the other two keeping your databases on the raid, it is always cheap to by one disk and install the OS that to loose your data.
Regards,
Terry
June 20, 2008 at 1:28 am
Space is no issue.
i have windows on separate physical disk
i have log on RAID1 separate disk ( as far as i know, RAID1 is better for larger reads)
i have data , currently, on RAID5, and space is not that much issue.
but issue is of speed. i have only four disks left for data. will it give better performance to have four disks (no raid) and separate filegroups or just one disk (RAID5) and, one single filegroup.
??????
June 20, 2008 at 8:21 am
Muhammad Furqan (6/20/2008)
Space is no issue.i have windows on separate physical disk
i have log on RAID1 separate disk ( as far as i know, RAID1 is better for larger reads)
i have data , currently, on RAID5, and space is not that much issue.
but issue is of speed. i have only four disks left for data. will it give better performance to have four disks (no raid) and separate filegroups or just one disk (RAID5) and, one single filegroup.
At some point, you need to balance performance with reliability. RAID was designed to provide an environment where you know you will not be losing any data. If a drive fails, you have time to replace it while the system remains running. I would NEVER put a database on a separate drive unless I was mirroring it to another server. If you lose the drive, you have lost your database and you are down until you replace the drive and restore the database. This would be the most expensive option since you'll need additional servers for the mirroring.
As far as the different RAID levels go, I would run RAID 10 for a high transaction database while RAID 5 is good for minimal transactions and mostly reporting. I would suggest reading up a bit on the different RAID levels before making a decision. Always make to use a Hardware RAID rather than Software RAID as the Software RAID is MUCH slower. Also, always make sure you have a dedicated Hot Spare for each array you set up.
In an ideal world (money not being an issue), setup a RAID 1 for your OS. This is basic mirroring and will keep you up and running should one of the drives fail. Use the entire drive since sharing drives across arrays will hurt performance. Then setup two RAID 10 arrays each with different drives (so you are not sharing), one for the data and the other for your log files. If you have separate databases used purely for reporting purposes, setup a separate RAID 5 array (again on different drives) for those databases.
June 20, 2008 at 8:30 am
Well Guys read this to know more about your RAID requirements:
http://sqlblog.com/blogs/linchi_shea/archive/2007/02/07/is-raid-5-really-that-bad.aspx
Maninder
www.dbanation.com
June 20, 2008 at 8:43 am
Mani Singh (6/20/2008)
Well Guys read this to know more about your RAID requirements:http://sqlblog.com/blogs/linchi_shea/archive/2007/02/07/is-raid-5-really-that-bad.aspx
Interesting read. Essentially, the responses to the blog indicate that testing in YOUR environment is the ONLY way to accurately find the best solution. There is a link provided in one of the responses that does provide the evidence that RAID 5 is bad in a high write environment. When you are penalized with more writes in a RAID 5 vs the alternatives, RAID 5 does accurately get a black mark.
http://www.miracleas.com/BAARF/1.Millsap2000.01.03-RAID5.pdf
This doesn't mean RAID 5 is bad for all environments as I stated above. It works great for report intensive environments where you are not heavy on the write side of the equation.
June 20, 2008 at 10:05 pm
that was very helpful 🙂
Thanks all
June 21, 2008 at 10:14 am
Read baarf and think about your environment. If you have lots of reads, I'd go with R1 or R10 for data, get the speed up there. You definitely want separate R1 for logs with lots of changes, since you have to log things and you want those disk heads always near the log writes.
Tempdb could be an issue in your environment and maybe you'd want an R1 volume for that.
Think about your environment, take some metrics and then make the best decision or come back here and give us your login and we'll debate it.
And keep a spare. The more disks, the more likely one will fail.
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