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What are you using instead of DCE Distributed File System? How does it compare? Or are you still using it?

Note that DCE/DFS is not Microsoft Distributed File System

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migrated from serverfault.com Feb 12 '11 at 20:09

This question came from our site for system and network administrators.

    
See also serverfault.com/questions/196285/… –  mattdm Feb 28 '11 at 17:59

3 Answers 3

I'm using AFS, NFSv3, NFSv4, and CIFS currently. CIFS is primarily for supporting Windows clients and I find it less suitable for UNIX/Linux clients since it requires a separate mount and connection for each user accessing the share. Users can share the same mount point, but they will be seen as the same user on the server-side of the connection.

NFSv3 is primarily used by directories being exported to other UNIX/Linux servers since it's stable and simple to deal with. With both AFS and NFSv4 I am using Kerberos. Using NFSv4 on Ubuntu 8.04 and older I found it a bit unstable, but it has steadily improved and I have no stability issues with 10.04+. It does appear to be a performance bottleneck to use sec=krb5p so I tend to use sec=krb5i or sec=krb5.

One issue I have is how Kerberos tickets are handled with Linux's NFSv4 layer. A daemon periodically scans /tmp for files beginning with krb5cc_ and matches the ticket up with the file owner. If a user has more than one ticket they own under /tmp, it will use whichever ticket file is found first when scanning. I've accidentally changed my identity when temporarily acquiring a ticket for other purposes. AFS stores tickets in Kernel-space and are associated with a login session normally. I can login twice as the same Linux user, but still use different AFS credentials on each login without interference. I also have to explicitly load credentials into the kernel which normally happens automatically during login. I can safely switch tickets in userspace without interfering with file permissions.

Overall, I like many of the ideas of AFS better than NFSv3/4, but it does have quite a bit smaller of a community developing it compared to NFS and CIFS. It's also properly known as OpenAFS, AFS is the name of IBM's closed-source offering. A big difference between AFS and NFS is that AFS is more consistent in it's network protocol and support. AFS does provide locking in-band instead of using a side-band protocol like NFSv3. It also offers a more sophisticated ACL system in-between POSIX ACLs and NFSv4/NTFS/CIFS ACLs. This, unlike the POSIX ACL addition to NFSv3, is a standard part of it's protocol and both Windows and UNIX/Linux clients can access and modify them. It also doesn't suffer from the 16 group limit that many NFSv3 servers have. This makes AFS appear more consistent in my mind across Windows and UNIX systems. Also, since AFS is only accessible via it's network protocol, there aren't issues where the actual underlying filesystem behaves slightly differently from the exported view of it. For example, in Linux, a file may have MAC or SELinux labels controlling access or other extended attributes that aren't visible over NFS. AFS, on the other hand just doesn't have extended attributes.

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AFS has some significant downsides worth mentioning. It requires a GPL-incompatible kernel module. (open source, but it still flags the kernel as tainted). And although it has ACLs, these are for directories only. Permissions on files in AFS are completely ignored. –  mattdm Jun 19 '11 at 20:58
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@mattdm I just wanted to point out quickly that the tainting issue is Linux only. One of the reasons I like OpenAFS is that it provides a more consistent environment across a variety of OSes even more so than NFS. OpenAFS is available with Windows, Mac OS X, Linux, Solaris, FreeBSD, and more. Also, ACLs, while attached to directories affect the files within the directory. A user must have insert permission on a directory to create a new file and write permission on the directory to write to any file within. Lastly, standard file owner permissions due take effect and affect everyone. –  penguin359 Jun 22 '11 at 0:54
    
Currently CIFS does support multi-user mounts on Linux when Kerberos authentication is used. –  grawity Sep 5 '11 at 8:19

I used Hadoop FS some time ago.

For instance, Hadoop documentation seems to be better than DCE/DFS. Also, it's developed actively. Earlier IBM provided support for DCE, but not anymore, at least actively. Point-to-point comparison is pretty hard, as I couldn't find any good feature lists for DCE/DFS. For Hadoop, see for example user guide.

Second, Hadoop with MapReduce provide powerful distributed computation platform.

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DCE/DFS always had at least 3 strikes against it:

  1. It was outlandishly complicated.
  2. It was costly.
  3. It was proprietary.

I know, they released DCE 1.1 as more-or-less open source, but by then, it was too late.

I've always had good luck with NFS, V3 or later, but then I'm not what you call a demanding user. I have the impression that a lot of places use Samba servers with CIFS, but I don't have direct experience.

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