July 23, 2013 at 3:55 pm
I'm guessing this could lead to a lot of theory and complex answers, however, I'm curious on your thoughts between RAID 5 and RAID 10. Yes, I realize that RAID 10 is faster than RAID 5, but is it fast enough to justify the potential cost hit (i.e. from what I've researched, 4k vs $10k). We are currently running a large set of databases with about equal distribution between reads and writes, leaning slightly towards writes. Figure into this about 1 million+ rows written per day. I am currently experiencing IO issues and have had some success by cleaning up indexes and performing other maintenance tasks. If I can prove that there will be a significant performance gain, it's possible we would consider switching to Raid 10. Any thoughts, experience, good article references?
Thanks.
July 23, 2013 at 4:59 pm
Hi,
What RAID type are your log files on ?
Are your db files on dedicated LUNs ?
Cheers
Vultar
July 24, 2013 at 11:21 am
1. Raid 5 Also (which I know is an issue)
2. Yes
July 24, 2013 at 12:38 pm
How are you coming up with $4k vs $10k?
Does not sound right.
July 25, 2013 at 2:07 am
Hi,
Getting the log files onto RAID 1, preferably 10 is a must to improve write performance, ideally, 1 file per LUN.
Have you considered trying RAID 1 for the data files instead of going straight to 10 ?
Have you tried a free MS tool called SQLIO ? This can help you determine the IO capacity of your current configuration.
You mentioned performing some general maintenance around indexes, etc.. also worth looking for queries with big scans / high reads, no SARGs, SELECT *, etc. What are your top IO waits in dm_os_wait_stats (server needs to of been running for a reasonable amount of time) ?
If you're really struggling to prove you need to move to RAID 10, you could be consider splitting the dbs into more files, spreading these over more LUNS and moving high read / write tables and indexes into these. It's a long winded solution and a bit of a pain because it would be better to just get a RAID 10 disk, but, if you're dbs are growing fast then it could prevent a future headache and give you more options at the same time.. particularly around partial restores.
Cheers
Vultar
July 26, 2013 at 2:31 pm
vultar (7/25/2013)
Hi,Getting the log files onto RAID 1, preferably 10 is a must to improve write performance, ideally, 1 file per LUN.
Have you considered trying RAID 1 for the data files instead of going straight to 10 ?
Have you tried a free MS tool called SQLIO ? This can help you determine the IO capacity of your current configuration.
You mentioned performing some general maintenance around indexes, etc.. also worth looking for queries with big scans / high reads, no SARGs, SELECT *, etc. What are your top IO waits in dm_os_wait_stats (server needs to of been running for a reasonable amount of time) ?
If you're really struggling to prove you need to move to RAID 10, you could be consider splitting the dbs into more files, spreading these over more LUNS and moving high read / write tables and indexes into these. It's a long winded solution and a bit of a pain because it would be better to just get a RAID 10 disk, but, if you're dbs are growing fast then it could prevent a future headache and give you more options at the same time.. particularly around partial restores.
Cheers
Vultar
Wouldn't a Raid 1 offer minimal performance benefits over a Raid 5?
I'll take a look into SQLIO, looks like it's a great tool.
I've been working with developers to clean up their code as well which has definitely helped. IO and os waits seem pretty good. I've found relatively few queries that run for extended periods of time and when I have, I recommend some query changes to the development team.
Thanks
July 26, 2013 at 4:03 pm
I have found without using SQLIO to really drill down into writes vs reads that generally RAID 10 will help with transactions log, but if there are equal or significant reads against the Database RAID 10 might hamper READ performance as compared to RAID 5.
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