Data and log files on separate disks

The production database of one of our clients is set up with both the data
and log files on the same disk. We suggested that they should separate them
out to eliminate disk contention and to eliminate I/O problems. The DBA at
the client site came back saying that he does not believe this is necessary.
Are we wrong in suggesting that the data and log files should be on separate
disks?
The client database is about 20 GB.
Thanks in advance."Frank1213" <Frank1213@.discussions.microsoft.com> wrote in message
news:80F4426D-0326-40D5-9EF4-B42853066EE6@.microsoft.com...
> The production database of one of our clients is set up with both the data
> and log files on the same disk. We suggested that they should separate
> them
> out to eliminate disk contention and to eliminate I/O problems. The DBA at
> the client site came back saying that he does not believe this is
> necessary.
> Are we wrong in suggesting that the data and log files should be on
> separate
> disks?
No, you're not.
However, whether it actually helps their performance is a good question.
If it's small enough and low volume enough, it won't help there.
If say the machine can only support 2 disks in a RAID 1 config, this
solution is "ok" given the machine.
If the machine can support more RAIDs (say 4 disks) then they're probably
better off separating them just because then if two disks fail, they're less
likely to actually suffer data loss.

> The client database is about 20 GB.
> Thanks in advance.
Greg Moore
SQL Server DBA Consulting Remote and Onsite available!
Email: sql (at) greenms.com http://www.greenms.com/sqlserver.html|||Thanks for the reply. As I mentioned the database is about 20GB and there is
plenty of activity during office hours and during other scheduled task runs.
Do you still believe separating the data and log files will improve some of
the bottlenecks.
Thanks
"Greg D. Moore (Strider)" wrote:

> "Frank1213" <Frank1213@.discussions.microsoft.com> wrote in message
> news:80F4426D-0326-40D5-9EF4-B42853066EE6@.microsoft.com...
> No, you're not.
> However, whether it actually helps their performance is a good question.
> If it's small enough and low volume enough, it won't help there.
> If say the machine can only support 2 disks in a RAID 1 config, this
> solution is "ok" given the machine.
> If the machine can support more RAIDs (say 4 disks) then they're probably
> better off separating them just because then if two disks fail, they're le
ss
> likely to actually suffer data loss.
>
>
> --
> Greg Moore
> SQL Server DBA Consulting Remote and Onsite available!
> Email: sql (at) greenms.com [url]http://www.greenms.com/sqlserver.html[/ur
l]
>
>|||"Frank1213" <Frank1213@.discussions.microsoft.com> wrote in message
news:9ABCC48E-C789-482F-8F42-D02AB663E307@.microsoft.com...
> Thanks for the reply. As I mentioned the database is about 20GB and there
> is
> plenty of activity during office hours and during other scheduled task
> runs.
> Do you still believe separating the data and log files will improve some
> of
> the bottlenecks.
Is it experiencing disk I/O bottlenecks?
If so, it would probably help. But again. 20GB and 'plenty of activity'
doesn't really tell enough to say for sure.
[vbcol=seagreen]
> Thanks
>
> "Greg D. Moore (Strider)" wrote:
>
Greg Moore
SQL Server DBA Consulting Remote and Onsite available!
Email: sql (at) greenms.com http://www.greenms.com/sqlserver.html|||Frank1213 wrote:
> Thanks for the reply. As I mentioned the database is about 20GB and there
is
> plenty of activity during office hours and during other scheduled task run
s.
> Do you still believe separating the data and log files will improve some o
f
> the bottlenecks.
> Thanks
>
Hi,
Maybe you should ask is the disk is in their SAN. It's true that in most
cases it's good practice to have your database and logfiles on seperate
disk - both for performance reasons but also for disaster recovery
reasons. There are a few cases where this doesn't really make any
difference though. If they e.g. are using a HP EVA SAN there isn't any
performance reason to have the files on different disks because in the
end these disk will share the same physical spindles. The EVA SAN simply
puts all the disks in one big diskgroup and then on top of that you can
create your virtual disks. This means that if you create 2 virtual disks
and present to a server, the server will see it as 2 disks. In the end
it's not any different than just creating 1 virtual disk and put
everything on that single virtual disk - it's still the same physical
spindles it puts the data on.
If this is the case with your customer that could be the reason for why
the DBA answers like he do.
Regards
Steen Schlter Persson
Database Administrator / System Administrator|||Thanks to both of you for your answers.
""Steen Schlüter Persson (DK)"" wrote:

> Frank1213 wrote:
> Hi,
> Maybe you should ask is the disk is in their SAN. It's true that in most
> cases it's good practice to have your database and logfiles on seperate
> disk - both for performance reasons but also for disaster recovery
> reasons. There are a few cases where this doesn't really make any
> difference though. If they e.g. are using a HP EVA SAN there isn't any
> performance reason to have the files on different disks because in the
> end these disk will share the same physical spindles. The EVA SAN simply
> puts all the disks in one big diskgroup and then on top of that you can
> create your virtual disks. This means that if you create 2 virtual disks
> and present to a server, the server will see it as 2 disks. In the end
> it's not any different than just creating 1 virtual disk and put
> everything on that single virtual disk - it's still the same physical
> spindles it puts the data on.
> If this is the case with your customer that could be the reason for why
> the DBA answers like he do.
> --
> Regards
> Steen Schlüter Persson
> Database Administrator / System Administrator
>