<a href="http://g.adspeed.net/ad.php?do=clk&zid=15220&wd=468&ht=60&pair=as" target="_blank"><img style="border:0px;" src="http://g.adspeed.net/ad.php?do=img&zid=15220&wd=468&ht=60&pair=as" alt="i" width="468" height="60"/></a>
Log in
::
Register
::
Not logged in
Home
Tags
Articles
Editorials
Stairways
Forums
Scripts
Videos
Blogs
QotD
Books
Ask SSC
SQL Jobs
Training
Authors
About us
Contact us
Newsletters
Write for us
<a href="http://g.adspeed.net/ad.php?do=clk&zid=15491&wd=120&ht=300&pair=as" target="_top"><img style="border:0px;" src="http://g.adspeed.net/ad.php?do=img&zid=15491&wd=120&ht=300&pair=as" alt="i" width="120" height="300"/></a>
Recent Posts
Recent Posts
Popular Topics
Popular Topics
Home
Search
Members
Calendar
Who's On
Home
»
SQL Server 2008
»
SQL Server 2008 Administration
»
RAID recomendations
17 posts, Page 1 of 2
1
2
»»
RAID recomendations
Rate Topic
Display Mode
Topic Options
Author
Message
Kenneth.Fisher
Kenneth.Fisher
Posted Wednesday, January 11, 2012 9:04 AM
Hall of Fame
Group: General Forum Members
Last Login: Thursday, May 09, 2013 8:31 AM
Points: 3,367,
Visits: 1,563
I'm starting to study for my Admin MCITP for 2008 and the first thing I have been hitting is the recommendations about what RAID to use for different parts of the server.
My understanding so far is that MS recommends a RAID 1 for Log files, and a RAID 5 for database files.
I have 2 questions.
What do the wise minds of SSC think of the above recommendations? For example wouldn't RAID 5 be better for the log since (from what I read) it provides better performance while still providing redundancy?
And would a RAID 0 be good for TEMPDB where you want fast performance but don't really need recoverability?
Kenneth Fisher
I strive to live in a world where a chicken can cross the road without being questioned about its motives.
--------------------------------------------------------------------------------
For better, quicker answers on T-SQL questions, click on the following...
http://www.sqlservercentral.com/articles/Best+Practices/61537/
For better answers on performance questions, click on the following...
http://www.sqlservercentral.com/articles/SQLServerCentral/66909/
Link to my Blog Post -->
www.SQLStudies.com
Post #1234076
GilaMonster
GilaMonster
Posted Wednesday, January 11, 2012 9:13 AM
SSC-Dedicated
Group: General Forum Members
Last Login: Today @ 12:59 PM
Points: 37,640,
Visits: 29,895
Best is 10 everywhere. If that's too expensive, then 1 or 10 for log and 5 for data (and 10 for TempDB)
RAID 5 is terrible for logs because it has a high write overhead. Tran logs are write-heavy, not read-heavy.
RAID 0 for TempDB is a risk, if any drive fails then TempDB fails and SQL shuts down. Now sure, there's no important data in there, but TempDB is essential for SQL operation and if it's on RAID 0 and a drive fails, SQL can't be started until either that failed drive is replaced (which could be anything from minutes to weeks) or until someone figures out how to start SQL without TempDB and relocates TempDB to some other drive.
Gail Shaw
Microsoft Certified Master: SQL Server 2008, MVP
SQL In The Wild
: Discussions on DB performance with occasional diversions into recoverability
We walk in the dark places no others will enter
We stand on the bridge and no one may pass
Post #1234092
azdzn
azdzn
Posted Wednesday, January 11, 2012 9:16 AM
UDP Broadcaster
Group: General Forum Members
Last Login: Tuesday, April 30, 2013 12:46 PM
Points: 1,493,
Visits: 239
Storage Top 10 Best Practices :
http://technet.microsoft.com/en-us/library/cc966534.aspx
Maybe there are no sensitive data in tempdb but you don't want your instance to shut down !
Post #1234098
Kenneth.Fisher
Kenneth.Fisher
Posted Wednesday, January 11, 2012 9:22 AM
Hall of Fame
Group: General Forum Members
Last Login: Thursday, May 09, 2013 8:31 AM
Points: 3,367,
Visits: 1,563
GilaMonster (1/11/2012)
Best is 10 everywhere. If that's too expensive, then 1 or 10 for log and 5 for data (and 10 for TempDB)
RAID 5 is terrible for logs because it has a high write overhead. Tran logs are write-heavy, not read-heavy.
I had thought that RAID 5 had better write performance than RAID 0? Although I have been reading comments in both directions.
RAID 0 for TempDB is a risk, if any drive fails then TempDB fails and SQL shuts down. Now sure, there's no important data in there, but TempDB is essential for SQL operation and if it's on RAID 0 and a drive fails, SQL can't be started until either that failed drive is replaced (which could be anything from minutes to weeks) or until someone figures out how to start SQL without TempDB and relocates TempDB to some other drive.
Excellent point. I hadn't thought of that.
Kenneth Fisher
I strive to live in a world where a chicken can cross the road without being questioned about its motives.
--------------------------------------------------------------------------------
For better, quicker answers on T-SQL questions, click on the following...
http://www.sqlservercentral.com/articles/Best+Practices/61537/
For better answers on performance questions, click on the following...
http://www.sqlservercentral.com/articles/SQLServerCentral/66909/
Link to my Blog Post -->
www.SQLStudies.com
Post #1234107
GilaMonster
GilaMonster
Posted Wednesday, January 11, 2012 9:28 AM
SSC-Dedicated
Group: General Forum Members
Last Login: Today @ 12:59 PM
Points: 37,640,
Visits: 29,895
Kenneth.Fisher (1/11/2012)
GilaMonster (1/11/2012)
Best is 10 everywhere. If that's too expensive, then 1 or 10 for log and 5 for data (and 10 for TempDB)
RAID 5 is terrible for logs because it has a high write overhead. Tran logs are write-heavy, not read-heavy.
I had thought that RAID 5 had better write performance than RAID 0? Although I have been reading comments in both directions.
No. RAID 5 has about the worst write performance of the common RAID levels because of the need to compute and then write parity. (though no one would ever consider RAID 0 for a database)
RAID 0, a write operation is a single operation. RAID 5 (let's say 4 stripes), a write operation is a write, potentially 1 or 2 reads and then a second write for the parity stripe)
There's a good overview of the RAID levels and more in chapter 2 of this:
http://www.simple-talk.com/books/sql-books/troubleshooting-sql-server-a-guide-for-the-accidental-dba/
Gail Shaw
Microsoft Certified Master: SQL Server 2008, MVP
SQL In The Wild
: Discussions on DB performance with occasional diversions into recoverability
We walk in the dark places no others will enter
We stand on the bridge and no one may pass
Post #1234117
Steve Jones - SSC Editor
Steve Jones - SSC Editor
Posted Wednesday, January 11, 2012 9:44 AM
SSC-Dedicated
Group: Administrators
Last Login: Yesterday @ 1:47 PM
Points: 31,406,
Visits: 13,722
I'd second Gail's advice. R10 if you can, R1 for logs if you can't. R5 for data if you must, but keep a spare drive around, which in most cases means you should just get 2 spares and go R10 anyway.
Follow me on Twitter:
@way0utwest
Forum Etiquette: How to post data/code on a forum to get the best help
Post #1234139
Kenneth.Fisher
Kenneth.Fisher
Posted Wednesday, January 11, 2012 10:48 AM
Hall of Fame
Group: General Forum Members
Last Login: Thursday, May 09, 2013 8:31 AM
Points: 3,367,
Visits: 1,563
Now I did see one comment that said if you can get a big enough RAID 10 (large number of disks) just stick it all in the same place and let the RAID controllers sort it out. I would guess that would in part depend on not just the # of disks but the # of controllers also correct?
Kenneth Fisher
I strive to live in a world where a chicken can cross the road without being questioned about its motives.
--------------------------------------------------------------------------------
For better, quicker answers on T-SQL questions, click on the following...
http://www.sqlservercentral.com/articles/Best+Practices/61537/
For better answers on performance questions, click on the following...
http://www.sqlservercentral.com/articles/SQLServerCentral/66909/
Link to my Blog Post -->
www.SQLStudies.com
Post #1234202
Steve Jones - SSC Editor
Steve Jones - SSC Editor
Posted Wednesday, January 11, 2012 10:51 AM
SSC-Dedicated
Group: Administrators
Last Login: Yesterday @ 1:47 PM
Points: 31,406,
Visits: 13,722
I think there's a limit whereby you are saturating channels, and it would depend on your workload. I think you want to minimize head movement if you have a busy log since these are sequential writes, and there is some benefit from having those separate.
For tempdb and data files, it's more workload dependent, but ultimately I would dislike having things together for risk purposes. I don't want to lose my log and my data (and my backups) if there is a problem with the array.
Follow me on Twitter:
@way0utwest
Forum Etiquette: How to post data/code on a forum to get the best help
Post #1234208
Kenneth.Fisher
Kenneth.Fisher
Posted Wednesday, January 11, 2012 12:43 PM
Hall of Fame
Group: General Forum Members
Last Login: Thursday, May 09, 2013 8:31 AM
Points: 3,367,
Visits: 1,563
I appreciate ya'lls help with this. RAID has always been a difficult subject for me but I think I'm finally getting it down.
Just as an aside, we have the interesting problem of not always knowing where are drives are comming from. In other words, the D drive and the E drive may actually both be on the same RAID array, but no one told us, its just the way it was allocated out.
Kenneth Fisher
I strive to live in a world where a chicken can cross the road without being questioned about its motives.
--------------------------------------------------------------------------------
For better, quicker answers on T-SQL questions, click on the following...
http://www.sqlservercentral.com/articles/Best+Practices/61537/
For better answers on performance questions, click on the following...
http://www.sqlservercentral.com/articles/SQLServerCentral/66909/
Link to my Blog Post -->
www.SQLStudies.com
Post #1234302
Evil Kraig F
Evil Kraig F
Posted Wednesday, January 11, 2012 12:53 PM
SSCertifiable
Group: General Forum Members
Last Login: Today @ 10:09 PM
Points: 5,658,
Visits: 6,100
Kenneth.Fisher (1/11/2012)
I appreciate ya'lls help with this. RAID has always been a difficult subject for me but I think I'm finally getting it down.
Just as an aside, we have the interesting problem of not always knowing where are drives are comming from. In other words, the D drive and the E drive may actually both be on the same RAID array, but no one told us, its just the way it was allocated out.
Very common in a SAN scenario. You usually have to work closely with the SAN team to get things setup physically the way you need them, but you'll almost always get pushback on this because it's 'wasteful' from their perspective unless you have a definate need and can prove I/O is your stall. It's up to you if it's worth the small war it can turn into, depending on your team. It might even be a friendly war, but you usually end up in one either way. SAN space is expensive a lot of places and it's their job to make sure it's used optimally from their side, too.
- Craig Farrell
Never stop learning, even if it hurts. Ego bruises are practically mandatory as you learn unless you've never risked enough to make a mistake.
For better assistance in answering your questions
|
Forum Netiquette
For index/tuning help, follow these directions.
|
Tally Tables
Twitter: @AnyWayDBA
Post #1234311
« Prev Topic
|
Next Topic »
17 posts, Page 1 of 2
1
2
»»
Permissions
You
cannot
post new topics.
You
cannot
post topic replies.
You
cannot
post new polls.
You
cannot
post replies to polls.
You
cannot
edit your own topics.
You
cannot
delete your own topics.
You
cannot
edit other topics.
You
cannot
delete other topics.
You
cannot
edit your own posts.
You
cannot
edit other posts.
You
cannot
delete your own posts.
You
cannot
delete other posts.
You
cannot
post events.
You
cannot
edit your own events.
You
cannot
edit other events.
You
cannot
delete your own events.
You
cannot
delete other events.
You
cannot
send private messages.
You
cannot
send emails.
You
may
read topics.
You
cannot
rate topics.
You
cannot
vote within polls.
You
cannot
upload attachments.
You
may
download attachments.
You
cannot
post HTML code.
You
cannot
edit HTML code.
You
cannot
post IFCode.
You
cannot
post JavaScript.
You
cannot
post EmotIcons.
You
cannot
post or upload images.
Copyright © 2002-2013 Simple Talk Publishing. All Rights Reserved.
Privacy Policy.
Terms of Use.
Report Abuse.
