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authorArne Babenhauserheide <arne_bab@web.de>2009-07-15 14:33:57 +0200
committerArne Babenhauserheide <arne_bab@web.de>2009-07-15 14:33:57 +0200
commit4ad8f285006b0edae8fe9c748714796a8dca9b6f (patch)
tree1d70776d6a753494b8211d48e75d99dda939e5c1 /community
parent6b3f1787ce364be0c025feeb3677c8e114eaf5e8 (diff)
weblog: Added Mail from olaf about the HUrd and plan9.
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+[[!meta copyright="Copyright © 2009 Free Software Foundation, Inc."]]
+
+[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
+id="license" text="Permission is granted to copy, distribute and/or modify
+this
+document under the terms of the GNU Free Documentation License, Version 1.2
+or
+any later version published by the Free Software Foundation; with no
+Invariant
+Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the
+license
+is included in the section entitled [[GNU Free Documentation
+License|/fdl]]."]]"""]]
+
+[[!meta title="Major differences between Plan9 and the Hurd"]]
+
+There are some similarities between the Hurd and Plan 9 regarding the file
+system handling -- but there are also very fundamental differences which go
+far beyond monolithic vs. microkernel design:
+
+- The Hurd is UNIX (POSIX) compatible
+
+- While (almost) all services are attached to the file system tree, not
+ all services actually export a file system interface!
+
+ Personally, I advocate using FS-based interfaces as much as possible.
+ Yet, there are some cases where they get very arward and/or
+ inefficient, and domain-specific interfaces simply make a lot more
+ sense.
+
+ Also, some Hurd services are indeed used to implement the file systems
+ in the first place -- they work below the FS level, and obviously
+ can't use an FS interface!
+
+- File systems are completely decentralized -- clients always talk to
+ the FS servers directly, without any central VFS layer. (I don't think
+ that's the case in Plan 9?)
+
+ This offers much more flexibility -- the way the FS interfaces
+ themselfs work can be modified. Many things can be implemented as
+ normal translators, that would require special VFS support on other
+ systems. (Extended attributes, VFS-based union mounts, local
+ namespaces, firmlink, magic file name suffixes etc.)
+
+- The system design allows users and applications to change almost all
+ aspects of the system functionality in the local environment easily
+ and without affecting other parts of the system.
+
+ (This is possible with Plan 9 to some extent; but the Hurd allows it
+ at a much lower level -- including stuff like the filesystem
+ interfaces, access control mechanisms, program execution and process
+ management, and so on.)
+
+I hope I didn't forget any major differences...
+
+*(copied from a Mail in the
+[[l4-hurd|mailing_lists#l4-hurd]]
+list).*