Coda File System

(Illustration by Gaich Muramatsu)

• News
• About
• Downloads
• Mailing lists
• Bugs
• FAQ
• Documentation
• Development
• Research
• Wiki

4. Volumes

Volumes are recorded using an umbrella data structure called the volume database (VDB), defined in venusvol.h.

• volume database. (persistent)
• contains volents (linked),
• contains mle
• resource limits on MLEs

Contained in the volume database are above all entries for individual volumes: volents. Volents are stored in persistent storage. Volents are described in venusvol.h as well and contain the following important fields:

• volume ID (of course)
• state (hoarding, emulating, logging (write disconnected),etc.)
• flags (state transition pending, reintegrating, repairing, weakly connected, etc.) counts (readers, writers, etc. for synchronization)
• range pre-allocated fids
• version vector, callback status
• list of read/write volume ids (if replicated)
• replicated volume id (if read-write)
• CML
• link to VSG entry (vsgent)
• list of FSOs
• list of COP2 pending (cop2ent)
• list of entries requiring resolution (resent)
• statistics (vmon, etc.)

A volume carries a client modification log. The umbrella data structure is the ClientModifyLog, which contains entries of type cmlent. These are all persistent. A structure of type ClientModifyLog has an owner, who is responsible for writing all the entries of the log. XXX What is an mle versus a cmle

• list of cmlents
• ownership (only one user may own)
• statistics

An entry in the CML is a higly technical structure reflecting the filesystem updates. It contains opcodes and a union (u) of data containing the fid and update details. All cmlents are held in RVM.

• opcode, operands
• flags (frozen, local repair, etc.)
• links to
  • CML
  • fsobjs
  • predecessor, successor

A very small structure holds the data associated to a cop2 event. This data is transient. cop2ent -- entry for pending COP2 events (transient)

• link to volume
• store ID
• update set

Another small structure holds data associated with fids needing resolution.

• resent -- entry for fids needing resolution (transient)
• fid, result