Take Off That Umask So We Can See You

Background

When a user creates a file in OS X, that file receives an initial set of permissions determined by the system's umask, or user file mode creation mask. The default umask in OS X dictates that the creator of a file has full read and write access, while everyone else has read-only access. This pesky default umask has bothered OS X users for quite some time. Users create files and drag them to server volumes shared by groups, only to realize that other group members can read the files, but not modify them. Collaboration is effectively broken, but not beyond repair ...

The private Ethernet network for metadata is one of the more obscure parts of an Xsan. The goal is to create a very low-latency communications channel for SAN metadata. In other words, when a client clicks "Capture Now," it needs to ask the metadata controller for the location of free space on the SAN. You want the metadata controller to return its response with no delay.

See below for some tips about this network.

Courtesy of Tekserve, here are two charts to illustrate how disks, RAIDs, and SANs are built up. Update 9 June 05: whack found a few errors in the original posted diagram. We've revised based on those comments. This is now the updated diagram.

Disks & RAID covers physical disks, arrays, partitions, slices, RAID sets, and volumes.

Xsan covers disks, LUNs, storage pools, affiinities, and volumes.

Over at AFP548.com, maccanada has posted a well-written article for how to spec out a small Xsan, with three SD and one HD edit stations.

Thomas Wolf describes why Avid and Xsan can't work together, and then explains how his company came up with a solution.