Vmware Using RDM's for shared Data Storage

We are trying to take this same approach. Multiple ESX servers, with mulitple hosts accessing a common "data" drive (on an EMC SAN w/ Navisphere and Access Logix) from IIS6. There is much benefit to this - a single location for deployment, easy backup, saved storage space (no need for data redundancy on a SAN) and various other items. Has anyone done this? If so, what was your approach?

We have tried to set up a file server in the middle, but are hitting a "BIOS connection limit" in Windows due to the large number of sites (and associated files) hosted on our virtual cluster.

We have tried presenting a Raw LUN to Vmware, mapping the drive in Windows as read-only, however, the obvious problem is that we don't see modifications to the file system on the windows machines unless the drive is unmounted and remounted (re-scanned).


We would like to stay away from having to push files to each esx server.


Any help would be greatly appreciated
viperhostAsked:
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Duncan MeyersCommented:
Unfortunately, what you want to do won't work in Windows (or VMware) as it results in irretrievable corruption.

A couple of solutions are: use a CIFS share for the shared data or a true shared file system such as Quantum's StorNext http://www.quantum.com/Products/Software/StorNext/Index.aspx
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viperhostAuthor Commented:
This is what I was affraid of, just after posting I found an article about Windows Unified Data storage server, I have not read too much about it but I am guessing from the overview this could do the trick?


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Duncan MeyersCommented:
'Fraid not. Windows Unified Data Storage Server does not change the essential nature of NTFS - you simply cannot have multiple servers trying to share the same NTFS file system.
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viperhostAuthor Commented:
Doesnt UDS server treat the volume as a share, then shared out via iSCSI? If not how does one create a webfarm with a single datastore?
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Duncan MeyersCommented:
It works in the same way as a NetApp filer or other NAS that offers file and block leel access. The block level LUN is stored as a file on he file system. You cannot have multiple access to a single NTFS disk from multiple servers at the same time
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viperhostAuthor Commented:
Is there anyway possible to do this? I am trying to create a web farm and really dont want to have thge same data in two seperate locations.
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Duncan MeyersCommented:
Yes. Use Quantum's StorNext file system as it allows multiple server access to one file system (a bit like VMware's VMFS but more sophisticated).
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Duncan MeyersCommented:
Alternatively, put the data on a Windows share.
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viperhostAuthor Commented:
I just tested a file share it works great except for the speed. The test page took about 25+ seconds to load opposed to testing it on a local drive where the page took less than 3 seconds to load all the content. I could not find any pricing on the StorNext application, but I am guessing it quit costly. There has to be a better solution for sharing data from two VM's.

I configured a RDM on the Storage server as a local disk and then shared it out, did I do something wrong that could effect the speed so greatly or is just just a caviot of sharing? Im on Gb switch with GB nics.
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Duncan MeyersCommented:
Windows Storage Server is not actually supported under VMware - which probably explains the poor performance. Try building a normal Windows server, put a file share on that, create an internal network that uses a NIC so that different ESX Servers can see it. Data transfers between the file share and a web server on the same ESX Server will run at memory speed, so you should see good performance.
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viperhostAuthor Commented:
Thnaks meyersd, Ill set it up and post back the results.
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viperhostAuthor Commented:
still no luck with speed, static content pulls ok, by dynamic content is very slow. I pose a new questions, If each server accesses the same LUN using iSCSI, can I use robocopy to populate the data on the second server our would this cause corruption to the data because ultimitly the data is on the same physical lun?
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viperhostAuthor Commented:
Ok, that was a dumb question, I am new to MSCS but from the way it sounds it would allow me to share a single volume accross multiple servers, I dont want to use MSCS for anything other than accessing the RDM from 4 servers, NLB will do the load balancing. Is this even possible, sorry to be so ignorant, but I am touching on new areas I have never worked with before and just trying to get it right.
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