AIX 5.3系统中如何设置>2G的大文件支持

AIX系统安装之后，默认不允许单个文件大小超过2G，对于企业应用系统来说，这个限制一般是需要去除的。

首先，取消安全方面的限制，需要修改配置文件/etc/security/limits，可以针对所有用户在default段修改，或者在指定user段来修改具体user的限制。下面是一个示例。设置成－1，表示取消大小限制。
cat /etc/security/limits

*
* Sizes are in multiples of 512 byte blocks, CPU time is in seconds
*
* fsize      - soft file size in blocks
* core       - soft core file size in blocks
* cpu        - soft per process CPU time limit in seconds
* data       - soft data segment size in blocks
* stack      - soft stack segment size in blocks
* rss        - soft real memory usage in blocks
* nofiles    - soft file descriptor limit
* fsize_hard - hard file size in blocks
* core_hard  - hard core file size in blocks
* cpu_hard   - hard per process CPU time limit in seconds
* data_hard  - hard data segment size in blocks
* stack_hard - hard stack segment size in blocks
* rss_hard   - hard real memory usage in blocks
* nofiles_hard - hard file descriptor limit
*
* The following table contains the default hard values if the
* hard values are not explicitly defined:
*
*   Attribute        Value
*   ==========    ============
*   fsize_hard    set to fsize
*   cpu_hard      set to cpu
*   core_hard         -1
*   data_hard         -1
*   stack_hard      8388608
*   rss_hard          -1
*   nofiles_hard      -1
*
* NOTE:  A value of -1 implies "unlimited"
*

default:
        fsize = -1
        core = 2097151
        cpu = -1
        data = -1
        rss = -1
        stack = -1
        nofiles = 65536
        maxuprc =1024
root:

daemon:

bin:

sys:

adm:

uucp:

guest:

nobody:

lpd:

oracle:
        fsize = -1
        core = 2097151
        cpu = -1
        data = -1
        rss = -1
        stack = -1
        nofiles = 65536

除了安全方面的限制，单个文件大小还受文件系统类型的限制，AIX下主要使用JFS和JFS2文件系统，下面是一个对比表格。可见，JFS最大只能支持64G的单个文件，有时候做大文件的归档备份时，有可能会超过这个限制的，所以建议使用JFS2文件系统。

Functions	JFS2	JFS
Fragments/Block Size	512-4096 Block sizes	512-4096 Frags
Maximum file system size	16 Terabytes	1 Terabyte
Maximum file size	16 Terabytes	64 GB
Number of i-nodes	Dynamic, limited by disk space	Fixed, set at file-system creation
Directory organization	B-tree	Linear
Compression	No	Yes
Quotas	No	Yes
Error logging	Yes	Yes