Explanation / use of read-only zoning feaure on MDS products

JUSTIN LOUCKS · ‎07-14-2006

Does anyone know if the MDS product line will work in this way when licensed with the Enterprise option for the read-only zoning?

I am trying to come up with a solution to provide real-time access to database files for a 2nd server that facilitates reporting applications. If I have LUNs that contain my primary database data and log volumes mapped to one server and create a 2nd read-only zone containing those LUNs, can I map those LUNs to a 2nd server as a kind of virtual/snapshot type instance?

I know that this will throw some odd things at the application side as it may or may not recognize the LUNs at read-only and could store things in temp tables or memory that would be cached and not actual current data but we've dealt with that in our reporting applications in the past utilizing snapshot technology on our storage platform. The downside to using that is in updating the snapshot to more recent copies, you have to at least offline the database to create a new snapshot with the same name/location which introduces interruptions, timeouts, etc.

Any feedback on how the read-only zoning feature is supposed to perform this type of functionality and/or real-world examples of how you are using it would be appreciated.

Thank you,

Justin Loucks

tblancha · ‎07-14-2006

Yes, the intent is to lock secondary devices to read the data but not able to write to it. So, the only caveat is that only certain filesystems are capable of mounting a partition RO. These include FAT16 and the Unix flavors and not NTFS. For a backup scenerio, you might also want to consider an offer we have called NASB. This is where the SSM handles the backup at the scsi level. It is new and you would have to check the OS and sw capatibility for your situation.

JUSTIN LOUCKS · ‎07-14-2006

Thanks for the feedback here. This is very helpful. It is a Windows/SQL server that the databases are sitting on so it will be a problem I guess.

Do you know if or think that it would work if the port Spanning type feature allow it to write all contents to a 2nd set of LUNs (kind of like syncronous mirroring in hardware) assuming you start with identical copies of the data on those LUNs. Could I potentially mount the 2nd set of LUNs to a server then or would the spanning session hold primary control to those and force me to do read-only zoning to see them again?

I know it isn't an optimal solution but I'm just trying to find some way to accomplish this...

JUSTIN LOUCKS · ‎07-14-2006

I guess I'm not sure how to read some of this when it references different versions of SAN-OS code and Operating system levels. For instance, in the documenation for SAN-OS 3.0, I found the following:

Read-only volumes are not supported by some operating system and file system combinations (for example, Windows NT or Windows 2000 and NTFS file system). Volumes within read-only zones are not available to such hosts. However, if these hosts are already booted when the read-only zones are activated, then read-only volumes are available to those hosts.

From -- http://www.cisco.com/en/US/products/ps5989/products_configuration_guide_chapter09186a0080662d35.html#wp1136509

Does this mean that as long as it is not my OS boot volume it may work? Also, it references NT and 2000 but not Windows 2003. Perhaps that is something that works differently now. I guess I'll open a case with MS on that to see what they say.

If anyone has already tried this or knows differently, please let me know. I just want to make sure I've exhausted all options here before I resort to Log shipping or some other software based solution.

dmcloon · ‎07-14-2006

On Windows 2003, after storing the files on the disk, set each file to read-only by right clicking the file name and ticking the read only file attribute. There is no way in Windows 2003 to set the whole disk as RO, and the read only attribute on a folder is ignored, it's used for other purposes. After making this change in Windows 2003, you can turn on the MDS read only zoning attribute. It does seem rather laborious if you have many files to mark as RO. That is how it was about 2 years ago. I am not sure if Windows 2003 behavior has since changed. This is something you would want to test in a lab.

cheers

Dallas