TITLE
    Mac OS X Server: About Mac OS Format Volumes
Article ID:
Created:
Modified: 		60117
3/11/99
10/31/00
TOPIC

    Release notes about Mac OS Format volumes for Mac OS X Server.

    Note: This document was installed by Mac OS X Server in /System/Documentation/ReadMe. For a list of other release notes see:
    Article 30925: " Mac OS X Server: Release Notes "

DISCUSSION

    Filesystem performance

    Filesystem performance on any Mac OS format disks (Standard or Extended) using Mac OS X Server will be dramatically affected by the allocation block size on a given disk or partition. The system is designed to accelerate input and output (I/O) only to files on volumes whose allocation block sizes are an even multiple of 4K; I/O to files on volumes with smaller or larger allocation blocks will be slower.

    Optimal Mac OS Standard format volume size ranges are 32 MB in size ending at multiples of 256 MB:
    • 224 - 256 MB
    • 480 - 512 MB
    • 736 - 768 MB
    • 992 - 1,024 MB
    • 1,248 - 1,280 MB
    • 1,504 - 1,536 MB
    • 1,760 - 1,792 MB
    • 2,016 - 2,048 MB

    For the best performance on a Mac OS Standard format disk, you should partition the disk using these size ranges.

    Allocation block sizes on Mac OS Extended format volumes are determined using a different algorithm and the allocation block size on these volumes will never be larger than 4 KB. Volumes under 2 GB will be created with increasingly larger allocation block sizes up to 4 KB and any volume or partition 2 GB or larger in size will be created with an allocation block size of 4 KB. Mac OS Extended disks or partitions should therefore be at least 2 GB in size for optimal performance.

    An easy way to verify the allocation block size on any disk is to use Get Info in the Finder to check the size of a small file. Alias files should take exactly one allocation block on disk. The size on disk should be 4 KB, 8 KB, 12 KB, 16 KB, or some other even multiple of 4 KB.

    Using Yellow Box or BSD applications

    Yellow Box and BSD applications, such as TextEdit, Emacs, and vi, were not written to make use of resource forks or certain other information associated with files on a Mac OS Standard or Mac OS Extended format disk. As a result, using these applications to open and save files created on Mac OS, Mac OS Compatibility on the Mac OS X Server, or AppleShare can lead to lossing the resource fork or other information, such as the Finder information which contains the type and creator of the file.

    Differences between Mac OS Standard and Mac OS Extended formats affecting MacOS X Server

    In addition to the usual advantages of the Mac OS Extended format, there are several features in the Mac OS X Extended format that are specific to Mac OS X Server operation. Because of these feature differences, you should always format Mac OS disks for Mac OS X Server using the Mac OS Extended format rather than Mac OS Standard format.

    The main differences follow:
    • Support for file and directory based permissions. Mac OS X server supports file and directory permissions the same way that BSD systems do. The Mac OS Standard format cannot store this information. All files and directories on Mac OS Standard format volumes have a universal permission set to allow read access to all users and both read and write access to root users and the Blue Box and cannot be changed. Attempting to change the owner, group, or permissions of a file on a Mac OS Standard format volume will not change any values, although no error message reports the failure. Mac OS Extended format volumes can store permission and other security information about files. If permissions have never been set for a file or directory on a Mac OS Extended format volume, the universal permission set is used. Users may, however, change the permissions on a file or directory on a Mac OS Extended format volume and those user set values will be stored and used.
    • Support for BSD file types. The Mac OS Standard format cannot store BSD file type information. This is especially noticeable with symbolic link files which are not supported on Mac OS Standard format volumes. The Mac OS Extended format can store this information, so link files are supported.
    • Support for AppleShare. You cannot share Mac OS Standard format volumes using Apple file services on Mac OS X Server, unless those volumes are on CD-ROM media.

Document Information
Product Area: Mac OS System Software
Category: Mac OS X Server
Sub Category: General Topics

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