Tuesday June 14, 2005

A new entry Soo apparently...a blog is suppose to contain multiple entries! Well, at least now, my blog has two entries--even if they are separated by about a year;-)
Since, I neglected to mention it in my first post, I will start with a bit of background on myself. I have been working as a developer with the Solaris Volume Manager(SVM) team for the last 1.5 years. My first assignment involved assisting with testing for the metaimport project. After the project was completed and backported to Solaris 9, I helped the other SVM engineers stabilize the SVM codebase for the Solaris 10 launch--i.e. fixed bugs. I am currently working on a project to extend some of the current functionality in SVM.

For those of you who are interested in learning more about SVM, I recommend that you at least scan the SVM documentation for system administrators. Since, I will be mentioning terms from the Solaris Volume Manager in my blog, I thought it might be helpful to briefly cover some of the concepts and the terms that we use internally to describe them.

• Logical Volumes
  • Logical volumes are used to manage physical devices and the associated data. These are also referred to as virtual disks or metadevices. SVM supports the following types of logical volumes(metadevices): stripes/concats, mirrors, soft partitions, hotspares, and raid5.
• Disksets
  • Disksets are used to group metadevices. Sets have their own state database replicas that contain information about all of the metadevices within the set. By default metadevices are placed in the local diskset, unless a specific set is specified. Specific sets are also called traditional disksets or shared disksets. There are also multi-owner(or multi-node) disksets, which are the only type of diskset that can be accessed by multiple hosts at the same time and are typically used with the Sun Cluster product.
• State database replicas
  • Information about all SVM metadevices is stored in state database replicas. These are also referred to as metadatabases or mddbs. These state database replicas(mddbs) typically exist in two places: on disk and in the kernel. In order to use SVM you must have created at least one mddb for the local set. The kernel keeps a copy of all active mddbs. These are referred to as the incore mddbs. The maximum size, which also happens to be the default size for a mddb(traditional or local set) is 4MB. The namespace for a diskset supports metadevice entries from d0 through d8191(not including hotspare pools).

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