Rescan takes 10 minutes

[eu22106]

Hi all,

I was wondering what the experience is about the duration of a rescan. In my environment (W2K3 SFWHA5.1 SP2 80 lun's) a rescan takes up to 10 minutes which I think is a very long time. Or am I too impatient?

Ivo

[Wally_Heim]

Hi eu22106,

Rescanning goes out and reads all disks that are on server.  You mention that you have 80 luns but do you have any DMP/multipathing going on.  Multiple paths per lun can cause a lot of delay because SFW has to scan the disk down all paths. 

So here is an example of what happens with multiple paths, lets say that you have 4 paths per lun for 80 luns.  This give SFW 320 luns that it has to read to know how to put them all together the 80 luns that you actually see.  When SFW reads the 320 devices that it physically sees it must determine if the device is new or if the device is already know.  If the device is new it has to create a MPIO lun for the device and addes a path to it.  In the end SFW has to handle 320 physical luns and it has to create/manage 80 virtual luns for this example for a total of 400 devices it has to manage.  Of course if you increase the paths you increase the number of devices that SFW has to handle.

With that said, you also mentioned that you are running 5.1 SP2 but you did not mention if any post SP2 CPs are installed.  Several of the initial CPs addressed issues with performance in the area of rescans.  If you are not running any CPs then you should think about installing one of the latest CPs available at:  https://sort.symantec.com/land.  CP14 is the latest that was just released last month.  I would recommend at least CP12 which was released a few months back.  You can search the sort site for "CP14" or "CP12" to find either of them.

FYI - CPs for the 5.1 SP2 product used to be released once a month.  However, now that we are releasing CPs for the 6.0 product monthly, the release schedule for CPs for the 5.1 SP2 product has been changes to quarterly.

Thank you,

Wally

[eu22106]

Wally, Thanks, for the quick repley.

Yes we have Multipathing in place with 8 paths.

I have installed CP10 (CP14 is in the planning). Nevertheless, do you feel that 10 miniutes is long for a environment that in effect had 8*80 Luns? Would you consider this a large site?
Ivo

[Wally_Heim · Accepted solution]

Hi eu22106,

10 minutes can be a long time.  I've seem some customers in the 45 minute timeframe.  It is all relative to what you as the customer see as a problem.  If you are already running CP10 then you have the performance improvements to the rescan that I was mentioning.

The rescan time also extends the time needed for boot.  A few things that I can recommend since you are running windows 2003, is to make sure that you check or update the following:

1. HBA firmware and drivers (hardware specific)

2. Storport.sys (Microsoft)

3. Mount manager drivers (Mircrosoft.)

4. The latest DDI package for 5.1 SP2.  This is a DMP/DSM update. (Symantec)

From there, if things are not improved, it might take more drastic configuration changes.  These are a few more drastic items to check.

1. As a simple configuration test, you could drop down to 4 paths per lun (or fewer) to see if the rescan times increase. 

2. Decrease the number of luns presented by presenting larger luns.  This will take some  planning as your existing volumes will need to be mirrored to the new larger luns.  The downfall here is depending on how you are using the existing luns, it might be hard or impossible to change to larger lun sizes.

Thank you,

Wally