Operating System Notes

All

     1. Shadow passwords 
        On any system with shadow passwords (including Solaris 2.5 with
        Unix authentication), read the SASL documentation carefully to make
        sure it is configured correctly. 

Solaris

     1. Modern Solaris systems have several useful utilities in
        /usr/proc/bin, among them pmap. This can be used to calculate the
        incremental cost (number of non-shared pages) of an imapd process,
        which is useful for sizing purposes. 

HP-UX

     1. The memory mapping support (mmap(2)) in HP-UX does not have the
        right semantics for the Cyrus IMAP server under the 9.0 and 10.0
        release of the operating system. It appears this is related to the
        hardware's use of inverse page tables. It is recommended that
        large-scale sites consider using some other platform. 

     2. HP-UX 9.0.4: Comments from testers 
        The C that ships with HP-UX is totally unsuited for use with unix
        packages. Either the HP-UX ANSI C developers kit must be purchased
        separately from HP or GNU's gcc compiler (which can bootstrap
        itself from the basic HP C) must be built on the target system. 

Linux

     1. synchronous FS updates. 
        By turning on synchronous updates for ext2fs, all updates (instead
        of just meta-data) become synchronous. This is good for
        reliability, but bad for performance. 

        The big problem used to be with the mailboxes file. The 2.0 release
        and later addressed this problem by changing the flat file to a
        Berkerley DB database. 

        Note this is for ext2fs. If you are using a newer filesystem (such
        as xfs, jfs, or reiserfs) the synchronous metadata issue shouldn't
        come up. Then again, we haven't really looked at other filesystems
        for Linux yet. (It appears that the different filesystems support
        slightly different semantics, and it's not always clear what the
        right thing for the application to do is.) 

