SQL Clone
SQLServerCentral is supported by Redgate
 
Log in  ::  Register  ::  Not logged in
 
 
 


RAID 1 vs. RAID 10


RAID 1 vs. RAID 10

Author
Message
Kendal Van Dyke
Kendal Van Dyke
SSCommitted
SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)

Group: General Forum Members
Points: 1644 Visits: 983
Lots of great articles on the intertubez about disk alignment and RAID configurations but I haven't found an answer (or a good way to test, and yes I know about SQLIO) for a simple scenario:

Suppose I have 4 local physical disks available to me and I'm going to create an OLTP DB (for the sake of arguing let's say we're 50\50 on reads and writes, or otherwise average usage). Here are two scenarios that I would consider:

1) Two RAID 1 drives. Create the DB with two data files, i.e. one data file on each drive
2) One RAID 10 drive. Create the DB with one single data file

In the RAID 1 scenario (as I understand it) SQL will round robin writes between the two data files, thus creating a software equivalent of striping. RAID 10, on the other hand, handles the striping at a hardware level. Those differences aside, I haven't found a good technical explanation - or numbers to back it - for what's happening under the covers that would make me believe one option is better than the other.

So which of these two scenarios is more ideal and why?

Kendal Van Dyke
http://kendalvandyke.blogspot.com/
Steve Jones
Steve Jones
SSC Guru
SSC Guru (147K reputation)SSC Guru (147K reputation)SSC Guru (147K reputation)SSC Guru (147K reputation)SSC Guru (147K reputation)SSC Guru (147K reputation)SSC Guru (147K reputation)SSC Guru (147K reputation)

Group: Administrators
Points: 147938 Visits: 19443
I would argue Raid 10 for one reason. You're not 100% sure of the usage and balance among the drives and with 2 R1s, you can run out of space on one, have space on the other. With one large R10, it gets handled and you get to use all the space.

Other than that, I'm not sure there's a great technical argument for R1 v R10.

Follow me on Twitter: @way0utwest
Forum Etiquette: How to post data/code on a forum to get the best help
My Blog: www.voiceofthedba.com
RBarryYoung
RBarryYoung
SSC-Dedicated
SSC-Dedicated (35K reputation)SSC-Dedicated (35K reputation)SSC-Dedicated (35K reputation)SSC-Dedicated (35K reputation)SSC-Dedicated (35K reputation)SSC-Dedicated (35K reputation)SSC-Dedicated (35K reputation)SSC-Dedicated (35K reputation)

Group: General Forum Members
Points: 35450 Visits: 9518
You should worry about your Log file before you add a second data file.

-- RBarryYoung, (302)375-0451 blog: MovingSQL.com, Twitter: @RBarryYoung
Proactive Performance Solutions, Inc.
"Performance is our middle name."
Kendal Van Dyke
Kendal Van Dyke
SSCommitted
SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)

Group: General Forum Members
Points: 1644 Visits: 983
RBarryYoung (12/23/2008)
You should worry about your Log file before you add a second data file.


Ummm....thanks....but kinda not the point of the post. I'm looking for technical reasons why a single data file on RAID 10 is better than two data files on two RAID 1's.

But FWIW I'll stick my log files on a different drive than my data files altogether. Hehe

Kendal Van Dyke
http://kendalvandyke.blogspot.com/
matt stockham
matt stockham
SSCrazy
SSCrazy (2.7K reputation)SSCrazy (2.7K reputation)SSCrazy (2.7K reputation)SSCrazy (2.7K reputation)SSCrazy (2.7K reputation)SSCrazy (2.7K reputation)SSCrazy (2.7K reputation)SSCrazy (2.7K reputation)

Group: General Forum Members
Points: 2652 Visits: 3178
I doubt that there is much difference from a performance standpoint ... the raid 1 scenario would presumably require a tiny increase in system resources. Raid 10 would appear to be a little easier to manage in as much as you would be dealing with one file rather than two. If I remember correctly, fragmentation statistics aren't accurate for multiple files either.

The above all assumes that the 2 files are across one filegroup (as that would use the proportional fill algorithm) - if one were to split the database into two filegroups (one file per filegroup) then there are other potential advantages from the raid 1 scenario .... filegroup backups, partitioning etc etc.
Mike John
Mike John
Hall of Fame
Hall of Fame (3.4K reputation)Hall of Fame (3.4K reputation)Hall of Fame (3.4K reputation)Hall of Fame (3.4K reputation)Hall of Fame (3.4K reputation)Hall of Fame (3.4K reputation)Hall of Fame (3.4K reputation)Hall of Fame (3.4K reputation)

Group: General Forum Members
Points: 3378 Visits: 5983
Another possible implication of two raid 1s would be if they were the same filegroup, with a massive table that was frequently being scanned. If I remember rightly in that situation (table scan, table on more than 1 file group) SQL Server will initiate multiple threads (one per file) and run the scans in parallel.

Mike



RBarryYoung
RBarryYoung
SSC-Dedicated
SSC-Dedicated (35K reputation)SSC-Dedicated (35K reputation)SSC-Dedicated (35K reputation)SSC-Dedicated (35K reputation)SSC-Dedicated (35K reputation)SSC-Dedicated (35K reputation)SSC-Dedicated (35K reputation)SSC-Dedicated (35K reputation)

Group: General Forum Members
Points: 35450 Visits: 9518
kendal.vandyke (12/23/2008)
I'm looking for technical reasons why a single data file on RAID 10 is better than two data files on two RAID 1's.

Ah, I see, I misunderstood the intent of your question. Sorry...

-- RBarryYoung, (302)375-0451 blog: MovingSQL.com, Twitter: @RBarryYoung
Proactive Performance Solutions, Inc.
"Performance is our middle name."
Kendal Van Dyke
Kendal Van Dyke
SSCommitted
SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)

Group: General Forum Members
Points: 1644 Visits: 983
Ah, I see, I misunderstood the intent of your question. Sorry...


No apologies necessary! Smile

Kendal Van Dyke
http://kendalvandyke.blogspot.com/
Perry Whittle
Perry Whittle
SSC Guru
SSC Guru (54K reputation)SSC Guru (54K reputation)SSC Guru (54K reputation)SSC Guru (54K reputation)SSC Guru (54K reputation)SSC Guru (54K reputation)SSC Guru (54K reputation)SSC Guru (54K reputation)

Group: General Forum Members
Points: 54801 Visits: 17694
i would say the RAID 10 array is best as it offers the best performance and fault tolerance combined into one package. The downside of RAID 10 is the disk cost (no of disks required)

-----------------------------------------------------------------------------------------------------------

"Ya can't make an omelette without breaking just a few eggs" ;-)
Kendal Van Dyke
Kendal Van Dyke
SSCommitted
SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)SSCommitted (1.6K reputation)

Group: General Forum Members
Points: 1644 Visits: 983
i would say the RAID 10 array is best as it offers the best performance and fault tolerance combined into one package. The downside of RAID 10 is the disk cost (no of disks required)


Maybe the question was misunderstood. I proposed two scenarios for how to configure 4 disks to hold data. A single RAID 10 with 4 disks is just as fault tolerant as two RAID 1 drives - each can lose 1 disk per pair. Likewise the disk cost is the same in the question I asked.

As for performance, I'm looking for something solid to show that RAID 10 would be better than RAID 1 or vice versa. I was really hoping someone knew enough about what's going on under the covers (e.g. IO paths, threads, etc.) to make it clear.

Kendal Van Dyke
http://kendalvandyke.blogspot.com/
Go


Permissions

You can't post new topics.
You can't post topic replies.
You can't post new polls.
You can't post replies to polls.
You can't edit your own topics.
You can't delete your own topics.
You can't edit other topics.
You can't delete other topics.
You can't edit your own posts.
You can't edit other posts.
You can't delete your own posts.
You can't delete other posts.
You can't post events.
You can't edit your own events.
You can't edit other events.
You can't delete your own events.
You can't delete other events.
You can't send private messages.
You can't send emails.
You can read topics.
You can't vote in polls.
You can't upload attachments.
You can download attachments.
You can't post HTML code.
You can't edit HTML code.
You can't post IFCode.
You can't post JavaScript.
You can post emoticons.
You can't post or upload images.

Select a forum

































































































































































SQLServerCentral


Search