Raid 1 vs Raid 10

Raid 1 is faster than Raid 10. The official stats are
operations per disk = (reads + writes) / number of disks
where as Raid 10 is...
operations per disk = (reads + (2 * writes )) / 2
However on my system I have Raid 10 for my log files. The
reason is that it offers the best combination of speed and
fault talerance, however it is not cheap, which is the
reason why we have raid 5 for our data files.
Get the book SQL Server 2000 Administrator Companion, ir
covers it in more detail.
Peter
"Action speaks louder than words but not nearly as often"
Mark Twain

>--Original Message--
>Hi,
>does anyone know where I can get soma stats on RAID
>efficiencies for SQL Server. Basically, I am interested
>in the difference between RAID 1 and RAID 10 for the
>transaction log. I realise that RAID 1 id the
>recommendation, but I need some data to convince the
>client that it is more appropriate.
>TIA,
>Jim
>.
>
I don't agree with Peter at all on the fact that Raid 10 is slower than Raid
1. The fact that a Raid 10 has twice the number of disks and can be smart
about how and when it reads and writes to each are a big advantage and can
make a difference in a very high volume system. The Raid 10 also gives much
better fault tolerance which can often be more of an advantage than sheer
speed anyway. Unless you are talking about many thousands of transactions
per second you probably won't notice a difference in speed between the two
any way. If you have the luxury of choosing between Raid 1 and 10 and it
doesn't take always disks / space etc. from any other array I would always
go for the 10. The reason why your hosting provider wants to go with Raid 1
over 10 is simply cost. I doubt that your doing enough trans per second to
warrant the extra cost of 10 and Raid 1 will suite most apps just fine.
Andrew J. Kelly SQL MVP
"Peter The Spate" <anonymous@.discussions.microsoft.com> wrote in message
news:7f9601c495a1$f8550050$a601280a@.phx.gbl...[vbcol=seagreen]
> Raid 1 is faster than Raid 10. The official stats are
> operations per disk = (reads + writes) / number of disks
> where as Raid 10 is...
> operations per disk = (reads + (2 * writes )) / 2
> However on my system I have Raid 10 for my log files. The
> reason is that it offers the best combination of speed and
> fault talerance, however it is not cheap, which is the
> reason why we have raid 5 for our data files.
> Get the book SQL Server 2000 Administrator Companion, ir
> covers it in more detail.
> Peter
> "Action speaks louder than words but not nearly as often"
> Mark Twain
>
|||RAID 10 should be faster than RAID1. See
RAID1
http://www.acnc.com/04_01_01.html
RAID10
http://www.acnc.com/04_01_10.html
I have done extensive testing on my hardware and also found that RAID5
was better than RAID1 for transaction logs. Bizarre, I know, but the
truth came out in the testing. So *on our hardware* we went with RAID5
for the transaction logs.
The moral of the story is, you need to benchmark different RAID levels
to get an accurate picture. Things don't always turn out as you expect.
If there's no way you can test your hardware before deciding, then RAID1
should be fine for you, but you *may* get a performance boost by using
RAID10 at considerable extra expense.
Mark Allison, SQL Server MVP
http://www.markallison.co.uk
Looking for a SQL Server replication book?
http://www.nwsu.com/0974973602m.html
Peter The Spate wrote:[vbcol=seagreen]
> Raid 1 is faster than Raid 10. The official stats are
> operations per disk = (reads + writes) / number of disks
> where as Raid 10 is...
> operations per disk = (reads + (2 * writes )) / 2
> However on my system I have Raid 10 for my log files. The
> reason is that it offers the best combination of speed and
> fault talerance, however it is not cheap, which is the
> reason why we have raid 5 for our data files.
> Get the book SQL Server 2000 Administrator Companion, ir
> covers it in more detail.
> Peter
> "Action speaks louder than words but not nearly as often"
> Mark Twain
>
>
|||Andrew is completely correct and I am completely wrong.
I even got the formulas mixed up.
Should of been
Raid 1
operations per disk = (reads + (2 * Writes)) / 2
Raid 10
operations per disk = (reads + (2 * writes)) / number of
disks.
I'm off to hide for a couple of days to get over the
shame, in thw meanwhile I will invent another person.
Peter
"The best argument against democracy is a five-minute
conversation with the average voter."
Winston Churchill

>--Original Message--
>I don't agree with Peter at all on the fact that Raid 10
is slower than Raid
>1. The fact that a Raid 10 has twice the number of disks
and can be smart
>about how and when it reads and writes to each are a big
advantage and can
>make a difference in a very high volume system. The Raid
10 also gives much
>better fault tolerance which can often be more of an
advantage than sheer
>speed anyway. Unless you are talking about many
thousands of transactions
>per second you probably won't notice a difference in
speed between the two
>any way. If you have the luxury of choosing between Raid
1 and 10 and it
>doesn't take always disks / space etc. from any other
array I would always
>go for the 10. The reason why your hosting provider
wants to go with Raid 1
>over 10 is simply cost. I doubt that your doing enough
trans per second to
>warrant the extra cost of 10 and Raid 1 will suite most
apps just fine.
>--
>Andrew J. Kelly SQL MVP
>
>"Peter The Spate" <anonymous@.discussions.microsoft.com>
wrote in message[vbcol=seagreen]
>news:7f9601c495a1$f8550050$a601280a@.phx.gbl...
The[vbcol=seagreen]
and[vbcol=seagreen]
often"
>
>.
>
|||Hey, we all make mistakes! :-) Except Andrew, he's a star.
Mark Allison, SQL Server MVP
http://www.markallison.co.uk
Looking for a SQL Server replication book?
http://www.nwsu.com/0974973602m.html
Peter The Spate wrote:
> Andrew is completely correct and I am completely wrong.
> I even got the formulas mixed up.
> Should of been
> Raid 1
> operations per disk = (reads + (2 * Writes)) / 2
> Raid 10
> operations per disk = (reads + (2 * writes)) / number of
> disks.
> I'm off to hide for a couple of days to get over the
> shame, in thw meanwhile I will invent another person.
> Peter
> "The best argument against democracy is a five-minute
> conversation with the average voter."
> Winston Churchill
>
|||be sure to get a Good RAID Controller with Cache and battery backup as well.
Also, the more disks, the better the performance so try to get as many disks
as possible.
example:
8 36GB Disks will perform better than 4 72GB Disks (Generally Speaking).
Greg Jackson
PDX, Oregon
|||Now we all know I have made a few mistakes here before as well. I think
Allan is the real star<g>...
Andrew J. Kelly SQL MVP
"Mark Allison" <marka@.no.tinned.meat.mvps.org> wrote in message
news:eOOvS6alEHA.2764@.TK2MSFTNGP11.phx.gbl...[vbcol=seagreen]
> Hey, we all make mistakes! :-) Except Andrew, he's a star.
> --
> Mark Allison, SQL Server MVP
> http://www.markallison.co.uk
> Looking for a SQL Server replication book?
> http://www.nwsu.com/0974973602m.html
>
> Peter The Spate wrote: