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Pre-Positioning Issues/Questions

jsrod
Level 1
Level 1

Hi all,

We are looking to do PC builds over the WAN, so in preparation we have pre-positioned the relevant 'build' files from the remote servers. However when we kick off a PC build, the PC is still downloading/running the files from the central server and as a result the WAN is running at 100% utilisation (not good!).

We have discovered that the PC is trying to pull down files from multiple core servers. The files are all the same on each core server, so it looks like we have to pre-position the files from each of the core servers. This means that we will potentially have to pre-position the same files (over 20GB worth) six times. Is there a way round this? I don't really want to pre-position 120GB worth of files unless I absolutely have to. The files on all the core servers are the same, so can we get the WAE’s to recognise that they already have the files - even though they have been pre-positioned from a  different server?

We have also discovered that the PC is looking for files within different folders on the same server. i.e. we have already pre-positioned 5GB worth of files from Folder A, but the PC is looking for the files in Folder B, which has not been pre-positioned. In summary, the files the PC needs exist in multiple folders on the same core servers, so do we have to pre-position the SAME files from the SAME server if they exist in different folders? I would of thought that the optimisers would be aware of the fact that they already had the files despite what remote server/folder the files were being requested from?

This testing tells me that the WAE's must ‘store’ files on their local disks based on the remote servers/folders, and that there must be some sort of correlation between the files/folders on the remote server and the files/folders stored on the optimsiers disks. Does the optimizer create a directory/folder structure that correlates to the remote servers/folders? If so is there a way to copy files between folders on the optimizers disks?

All the files we need exist on different core servers and also within different folders on each server. The files all have the same properties - and we have already pre-positioned the files from one server/folder. So why aren't the WAE’s not recognising that they already have the files pre-positioned - albeit from a different server/folder?

I have searched on-line and gone through all the documentation but I cannot find any answers to my questions.

Hope someone can help - we are really struggling with this and need to get some answers in order to proceed with the roll-out.

Many Thanks,

Jamie.

1 Reply 1

Hi Jamie,

You are correct, your PC build files that were part of the preposition job are stored in the CIFS cache within a directory structure which correlates to the specific server (the same goes for on demand CIFS caching as well).  So, as you have found if you preposition file A from server X, but then when your client accesses file A from server Y, this will be a CIFS cache MISS (assuming file A wasn't accessed via server A by another client or preposition job).  However, you will receive a DRE cache hit, assuming the relevant DRE signatures that represent the bytes for file A have not been aged out.

So, however your files are prepositioned (//serverX/fileA), that is how your clients must access them in order to receive a CIFS object cache hit (e.g. pull the whole file from local WAE CIFS cache). 

There is no way to "move" files within the directory structure on the CIFS cache as this is not exposed via the CLI, nor would we want to be able to do that since it would break coherency models.

Thus, I'd suggest you point your clients to the same server or subset of servers for all of their files and preposition those specific server shares to the client side WAEs.

Example:

Site 1, accesses servers A & B during the build process; setup a preposition job for servers A & B and assign the site 1 WAE to that job.

Site 2, accesses server C  & D during their build process; setup a preposition job for servers C & D only and assign the site 2 WAE to that job.

Etc...

As for the multiple folders question, you can select more than 1 folder to be prepositioned when you create the job on the CM (use the browse feature when creating the job to select individual folders).  If these folders are sub-directories of the folder you specified, make sure the check box for "Incude Sub Directories" is selected.

I hope this helps clarify how WAAS CIFS caching operates.

Regards,

Mike Korenbaum

Cisco WAAS PDI Help Desk -

http://www.cisco.com/go/pdihelpdesk

P.S.  If this answers your question please mark it as such; Thanks!

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