[Okta Webinar] Learn how to a build a cloud-first strategyRegister Now

x
  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 3513
  • Last Modified:

Windows Server 2008 R2 Maximum number of SCSI ID's

Hi,

What is the maximum number of SCSI ID's Windows Server 2008 R2 can handle? Our SAN team have allocated 306 SCSI ID's for LUNS but when they try and allocate LUNS with SCSI ID's over this number the Windows Server cannot see them.

Our SAN team seem to think there must be a SCSI limit of 306 on Windows Server 2008 R2, although this number does seem a bit random.

Could anyone confirm what the maximum number of SCSI ID's Windows Server 2008 R2 can handle please?

Many thanks in advance!
0
sjbarnes
Asked:
sjbarnes
  • 4
  • 3
  • 3
  • +2
1 Solution
 
Felix LevenCommented:
Hi,

i am pretty sure there is a limit but as you already stated "a bit random". I looked through all the "Windows Server 200X Storage limit" guides and searched the Hyper-V, MS Storage Server Guides/Limits Whitepapers and the limits are 255.

HP states above 255 will not work:
http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=c02730973&lang=en&cc=us&taskId=101&prodSeriesId=4132949&prodTypeId=3709945

And  i can't assign higher ID's in IBM Storage Manager for example, so i would think this is a limit to SCSI. Vmware also has a problem with ID's 254+

0
 
remixedcatCommented:
There are also per LUN limits as well.
0
 
remixedcatCommented:
You can have up to 256 LUNs per host, and up to 8 paths to each of those LUNs.
0
What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

 
remixedcatCommented:
256 luns * 4 paths each, or 128 luns with 8 paths each
0
 
Gerald ConnollyCommented:
Doesnt your RAID array/SAN present server based LUN numbers to each server?
0
 
kevinhsiehCommented:
Why would you ever want anything close to 255 LUNs on a server? Back before Hyper-V 2008 R2 when I had 1 LUN per VM I would get up to 20 LUNs or so but hundreds of LUNs on a server doesn't seem like a good idea.
0
 
Gerald ConnollyCommented:
Kevin, i think he means that the LUN numbers are up in the 300's not that he has 300 LUNs or i hope thats what he means!

All the storage systems i have worked with have always had a mechanism to present the server with the LUN number of your choice.
0
 
sjbarnesAuthor Commented:
Hi,

Thanks for the info. It does now look like the SAN has a limit to provide 255 SCSI ID's, not really my area of expertise.

We require this numer of LUNS due to implimenting Exchange 2007 in a 3 Active server/1 Passive server config with a total 50 SG to per server. Microsoft recommend 1 x LUN for DB and 1 x LUN for LOGS this totals 100 LUNS per server, and as this is a cluster each server needs to see each others LUNS for failover etc so thats where the 300 LUNS comes from..........
0
 
Gerald ConnollyCommented:
So you have 100 tiny LUNs per server? Seems like overkill?

How are these LUNs implemented in the SAN as it sounds like this scheme could be very wasteful in terms of the number of disks.
0
 
sjbarnesAuthor Commented:
Hi,

Yeah we have 100 LUNS per server. May seem like overkill but it is needed as we are talking about potentialy hosting 23,000 mailboxes!
0
 
Gerald ConnollyCommented:
@sjbarnes re SCSI ID's i think you are confusing two issues here.

1) There is probably a limit to the total number of LUNs your SAN can provide, but i suspect its much higher than 255 (What is your SAN by the way?)

2) There is a limit on the SCSI ID's that Windows can cope with as already defined previously.

Your SAN can probably present any of its LUNs as a local SCSI ID to each server, so that SAN LUNs 10-19 that are presented as SCSI ID 10-19 to Server-1, and SAN LUNs 20-29 that are presented as SCSI ID to 10-19 to Server-2 (and i really mean presented as the same SCSI ID's). This will get round the issue of SCSI ID's at the server level, but if you really want to have all the Exchange Databases etc potentially presented to every server you need to consolidate the number of SG's per server and also take into account that you also need to take into account multiple paths to the storage as well.

You only need to double up the mailboxes per SG, or run multiple SG's per LUN to achieve what you want to do.
0
 
sjbarnesAuthor Commented:
Hi Connollyg,

Sorry for any confusion but I don't deal with the SAN myself.

The SAN team have now set the SCSI ID's as you have recommended and all appears to be fine now.

Thanks!
0

Featured Post

Simplify Active Directory Administration

Administration of Active Directory does not have to be hard.  Too often what should be a simple task is made more difficult than it needs to be.The solution?  Hyena from SystemTools Software.  With ease-of-use as well as powerful importing and bulk updating capabilities.

  • 4
  • 3
  • 3
  • +2
Tackle projects and never again get stuck behind a technical roadblock.
Join Now