> Some of the downsides of using disk as disk are > > 1) Concurrency to disk: if you have multiple media servers, how to ensure > they're cooperating peacefully when reading/writing to the same disk area. > You can do that in several ways: > > * Divide up in separate LUNs. Each media server owns it and creates > a file system on it. Very difficult to change the amount allocated to each. > Maybe a volume manager and advanced file system can address some of that. > > * Cluster file system. Good solution. Introduces complexity and > potentially cost. > > * "Gentleman's agreement" sharing of LUN. Access to files are > centrally brokered by the master server. I believe this is how CommVault > Galaxy/GridStor operates. The servers asks broker politely before writing to > a certain disk area. Not a true cluster file system. > > *
The way that CommVault does it with Gridstor is that each media server shares an index cache (the equivalent of NBU's catalog/databases) via NFS or CIFS. I call it a "poor man's clustered filesystem". It affords one the luxury of pooling media servers, such that if one goes down, any other can take over in it's place. Since the index cache is shared, the job just picks up where it left off. It also allow one to load balance among media servers. The same goes for disk storage targets. If disk storage unit "A" becomes unavailable for any reason, disk STU "B" can be configured to take over in it's place. Massive job and component resiliency! -- =================================== Steven L. Sesar Lead Operating Systems Programmer/Analyst UNIX Application Services R101 The MITRE Corporation 202 Burlington Road - MS K101 Bedford, MA 01730 tel: (781) 271-7702 fax: (781) 271-2600 mobile: (617) 519-8933 email: [EMAIL PROTECTED] =================================== _______________________________________________ Veritas-bu maillist - Veritas-bu@mailman.eng.auburn.edu http://mailman.eng.auburn.edu/mailman/listinfo/veritas-bu