raid 5 v raid 10

We are looking to run a web based CRM package that runs on SQL 2005.
It has been recommend that we set the it up with RAID 5 however on
reading up on this it looks like RAID 10 could be better option.
The hard ware spec so far is for RAID 5
2 * 72.6 GB Hard Drives for the operating system
3 * 146.8 GB Hard Drives the database.
If were to go for RAID 10, as to requires equal number of drives I
presume that we would need to up it from 3 to 4.
What are other peoples experiences/views
If you have over 20% of your IO activity is write based IO you will get
better performance with RAID 10. While RAID 5 is more expensive than RAID
10 typically the performance gains offset this added cost.
Hilary Cotter
Looking for a SQL Server replication book?
http://www.nwsu.com/0974973602.html
Looking for a FAQ on Indexing Services/SQL FTS
http://www.indexserverfaq.com
"jp" <jeremypw@.googlemail.com> wrote in message
news:1168248735.954175.305990@.s34g2000cwa.googlegr oups.com...
> We are looking to run a web based CRM package that runs on SQL 2005.
> It has been recommend that we set the it up with RAID 5 however on
> reading up on this it looks like RAID 10 could be better option.
> The hard ware spec so far is for RAID 5
> 2 * 72.6 GB Hard Drives for the operating system
> 3 * 146.8 GB Hard Drives the database.
> If were to go for RAID 10, as to requires equal number of drives I
> presume that we would need to up it from 3 to 4.
> What are other peoples experiences/views
>
|||"Hilary Cotter" <hilary.cotter@.gmail.com> wrote in message
news:%23Uzk0HxMHHA.5012@.TK2MSFTNGP02.phx.gbl...
> If you have over 20% of your IO activity is write based IO you will get
> better performance with RAID 10. While RAID 5 is more expensive than RAID
> 10 typically the performance gains offset this added cost.
Uh, I think you mean while RAID 5 is LESS expensive than RAID 10?

> --
> Hilary Cotter
> Looking for a SQL Server replication book?
> http://www.nwsu.com/0974973602.html
> Looking for a FAQ on Indexing Services/SQL FTS
> http://www.indexserverfaq.com
>
> "jp" <jeremypw@.googlemail.com> wrote in message
> news:1168248735.954175.305990@.s34g2000cwa.googlegr oups.com...
>
|||Hi,
Well, actually, RAID 10 could outperform RAID 5, especially because of
that CRM uses a lot of random writes which is the black point of RAID 5
level.
The theory is the following, assuming you have n similar disks :
RAID 5 Write time : 1/(n-1)
RAID 10 Write time : 1/(n/[number of disks per RAID 1 set])
RAID 5 Read time : 1/(n-1)
RAID 10 Read time : 1/n
RAID 5 fault tolerance : 1 disk
RAID 10 fault tolerance : [number of RAID 0 sets] * ([number of disks
per RAID 1 set] - 1)
Nevertheless, this is only theory... And here are some of the problems
in the real life :
- While updating small sets of data (just as you might do in a CRM
application), you make a random write... Thus, in RAID 5, the
controller has to re-read the entire stripe to write the parity blocks.
Which dramatically brings down the RAID 5 performances... As you double
the theorical write time...
- While inserting large amounts of data, you make a sequential write...
Thus RAID 5 would be much more efficient than any other RAID level,
assuming you need fault tolerance.
- While reading either small sets of data or large amounts of data,
RAID 5 is a little bit slower than RAID 10...
- RAID 5 loses much less disk capacity than RAID 10, and as so is much
cheaper.
In conclusion you might use RAID 10 if your application needs a lot of
random writes... However, as a matter of cost, I would recommand you to
keep RAID 5 and to add a third set of drives to store transaction logs.
In many cases I've came accross, the I/O bottleneck raises because of
the usage of the same set of disks for data and transaction log... As
RAID 5 wouldn't have been a real problem...
Cdric Del Nibbio
MCSD .NET
MCTS SQL Server 2005
http://cedric-delnibbio-sql.blogspot.com
jp a crit :

> We are looking to run a web based CRM package that runs on SQL 2005.
> It has been recommend that we set the it up with RAID 5 however on
> reading up on this it looks like RAID 10 could be better option.
> The hard ware spec so far is for RAID 5
> 2 * 72.6 GB Hard Drives for the operating system
> 3 * 146.8 GB Hard Drives the database.
> If were to go for RAID 10, as to requires equal number of drives I
> presume that we would need to up it from 3 to 4.
> What are other peoples experiences/views
|||Thanks Strider - you're right - RAID 10 has a minimum of 4 drives and 50%
utilization. RAID 5 needs a minimum of 3 drives with n-1 utilization.
So RAID 5 is cheaper.
Hilary Cotter
Looking for a SQL Server replication book?
http://www.nwsu.com/0974973602.html
Looking for a FAQ on Indexing Services/SQL FTS
http://www.indexserverfaq.com
"Greg D. Moore (Strider)" <mooregr_deleteth1s@.greenms.com> wrote in message
news:u1D1dLyMHHA.2456@.TK2MSFTNGP06.phx.gbl...
> "Hilary Cotter" <hilary.cotter@.gmail.com> wrote in message
> news:%23Uzk0HxMHHA.5012@.TK2MSFTNGP02.phx.gbl...
>
> Uh, I think you mean while RAID 5 is LESS expensive than RAID 10?
>
>
>
|||Theoretical pros and cons aside, whether or not you need a three-plus-drive
RAID5 or a four-plus-drive RAID10 should be determined by the I/O
requirements of your app(s), and that only you or your app folks can answer.
You can look at some of your previous perfmon counters for clue.
Alternatively, you can run some tests to get an even more accurate estimate.
It's possisle that RAID5 can provide sufficient I/O throughput to meet your
requirements.
Linchi
"jp" wrote:

> We are looking to run a web based CRM package that runs on SQL 2005.
> It has been recommend that we set the it up with RAID 5 however on
> reading up on this it looks like RAID 10 could be better option.
> The hard ware spec so far is for RAID 5
> 2 * 72.6 GB Hard Drives for the operating system
> 3 * 146.8 GB Hard Drives the database.
> If were to go for RAID 10, as to requires equal number of drives I
> presume that we would need to up it from 3 to 4.
> What are other peoples experiences/views
>
|||for writing process Raid 5 is MORE expensive from performance point of view
;-)
not from a money point of view where Raid 5 is cheaper then raid 10 for the
same usable disk space. (3 disks in raid 5 = 4 disks in Raid 10, so cheaper
for the same space but less performance)
"Greg D. Moore (Strider)" <mooregr_deleteth1s@.greenms.com> wrote in message
news:u1D1dLyMHHA.2456@.TK2MSFTNGP06.phx.gbl...
> "Hilary Cotter" <hilary.cotter@.gmail.com> wrote in message
> news:%23Uzk0HxMHHA.5012@.TK2MSFTNGP02.phx.gbl...
>
> Uh, I think you mean while RAID 5 is LESS expensive than RAID 10?
>
>
>
|||Thanks for the info
Linchi Shea wrote:[vbcol=seagreen]
> Theoretical pros and cons aside, whether or not you need a three-plus-drive
> RAID5 or a four-plus-drive RAID10 should be determined by the I/O
> requirements of your app(s), and that only you or your app folks can answer.
> You can look at some of your previous perfmon counters for clue.
> Alternatively, you can run some tests to get an even more accurate estimate.
> It's possisle that RAID5 can provide sufficient I/O throughput to meet your
> requirements.
> Linchi
> "jp" wrote:
|||Thanks for the info
Linchi Shea wrote:[vbcol=seagreen]
> Theoretical pros and cons aside, whether or not you need a three-plus-drive
> RAID5 or a four-plus-drive RAID10 should be determined by the I/O
> requirements of your app(s), and that only you or your app folks can answer.
> You can look at some of your previous perfmon counters for clue.
> Alternatively, you can run some tests to get an even more accurate estimate.
> It's possisle that RAID5 can provide sufficient I/O throughput to meet your
> requirements.
> Linchi
> "jp" wrote: