SAN Storage setup - 44 Luns all shared by ECC, BW and PI

[Former Member]

The storage team setup our EMC SAN for production ECC, BW, and PI to share 44 Lun's. I discovered this once I got onto this project....we have not gone live yet.....that is 3 months away.

So, my obvious question is - will this configuration not cause an I/O Bottleneck ?

A second 'problem' I discovered is that 12 Luns have a starting offset of 65536 (64k) while the others are properly starting at 1048576 (1024k) for Windows 2008. Do you see a problem here with different LUN's using 2 different startingOffsets??

Thanks for any feedback....

I should also mention we are using Mount Points with SQL Server 2008 Clustered.

Linwood

Edited by: Linwood Doty on Dec 19, 2011 6:18 PM

[markus_doehr2]

> The storage team setup our EMC SAN for production ECC, BW, and PI to share 44 Lun's. I discovered this once I got onto this project....we have not gone live yet.....that is 3 months away.

>

> So, my obvious question is - will this configuration not cause an I/O Bottleneck ?

A LUN is just a logical assignment, the question is, how are the harddisks distributed behind it.

> A second 'problem' I discovered is that 12 Luns have a starting offset of 65536 (64k) while the others are properly starting at 1048576 (1024k) for Windows 2008. Do you see a problem here with different LUN's using 2 different startingOffsets??

check the following blog:

http://blogs.msdn.com/b/jimmymay/archive/2009/05/08/disk-partition-alignment-sector-alignment-make-t...

> I should also mention we are using Mount Points with SQL Server 2008 Clustered.

mount points?

Markus

[Former Member]

Hi There,

Each LUN = 1 disk ( so we have 44 Disks that are all shared together with all three systems). Also the transaction logs are located on these same set of 44 disk !

Thanks for the link to the info on disk alignment.....and I do understand the importance. I quess my question was how having some of these 44 disk aligned differently than the others (like 12 or so are aligned "startingOffset" 64k....while the rest are aligned "startingOffset" 1024k....which is correct. (the block/cluster size is 4096 which I know is wrong also but that's another issue).

Mount Points....here's a brief on them....

http://www.windowsitpro.com/article/file-systems/the-magic-of-mount-points

and an issue with sapinst using them...

http://blogs.msdn.com/b/saponsqlserver/archive/2011/06/10/sap-on-sql-installation-on-mount-points.as...

Thanks!

Linwood

[markus_doehr2]

> Each LUN = 1 disk ( so we have 44 Disks that are all shared together with all three systems). Also the transaction logs are located on these same set of 44 disk !

So you could have the choice of using 10 for each system plus 1 for the log area? despite of "seeing" them all?

> Thanks for the link to the info on disk alignment.....and I do understand the importance. I quess my question was how having some of these 44 disk aligned differently than the others (like 12 or so are aligned "startingOffset" 64k....while the rest are aligned "startingOffset" 1024k....which is correct. (the block/cluster size is 4096 which I know is wrong also but that's another issue).

This may be caused by the way the SAN presents them to the server, it may be a limitation of the SAN-drivers used on Windows (mapping to old SCSI interfaces) or any other software mapping in between. Difficult to say from here. It can also be that, depending on which SAN you use, that just the wrong operating system for the presentation of the disk was chosen.

> Mount Points....here's a brief on them....

Got it, I knew that was existing on Windows, but never used it though and wasn't aware, that it's really called "mount point", I'm mainly workign on *NIX systems.

Can't say about anything SAP related to that point.

Markus

[Former Member]

> Each LUN = 1 disk ( so we have 44 Disks that are all shared together with all three systems). Also the transaction logs are located on these same set of 44 disk !

So you could have the choice of using 10 for each system plus 1 for the log area? despite of "seeing" them all?

I don't have a choice ....I just select my mount point (drive letter and subdirectory) where I want to install the sapdata's and Log. I quess I need to find out how they have carved out space on these drives and then come back here....I wanted to get some feedback though before I get with them.....

If all three systems are all stripped across all 44 disks then that has got to be "not good".....I will find out.

Thanks for your time...

Linwood

[Former Member]

Update:

I did confirm each instance has dedicated LUNs....so that's a non-issue.

I'm still faced with the fact that the NTFS file allocation is at 4k as opposed to 64k.

So now I am left with a NTFS file allocation of 4k which I will have to live with unless stress testing is a disaster...then I will have a good argument to reformat the drives to 64k..

thanks...

Ld

[markus_doehr2]

> I'm still faced with the fact that the NTFS file allocation is at 4k as opposed to 64k.

Reformat the device if you haven't started an installation yet, it's a matter of minutes

Markus