(r5) Upgrade64 < Main

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---+!! Upgrading the Nevis Linux cluster to a 64-bit operating system

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---++ Upgrade schedule

| *Date* | *Systems* | *Mail affected* |
| Tue 17-Aug-2010 | morningside, riverside | Neutrino group, willis |
| Thu 19-Aug-2010 | shang, han | DOE Group, shaevitz, annmarie, jsantini, bishop, capone |
| Tue 24-Aug-2010 | karthur | D0/ATLAS, ban, zhang |
| Wed 25-Aug-2010 | kolya | ATLAS group |
| Thu 26-Aug-2010 | tehanu | VERITAS group |

Each upgrade will start at 4PM, and will hopefully take no more than two hours.

*Important*: While any of the above servers are being upgraded, there is a good chance that the mail server will slow down. It might be necessary to reboot the mail server before and/or after the upgrade.

The batch nodes (=hermesXX=, =kennelXX=) and 64-bit-compatible workstations will be upgraded during those two weeks.

---++ Which systems won't be upgraded

The following systems won't be upgraded to 64-bit; at least, not as part of this co-ordinated effort. Instead, as the systems are replaced, their replacements will receive a 64-bit version of Linux.
<ul>
<li><tt>westside.nevis.columbia.edu</tt>, a Neutrino server that will be reserved for compiling the SciBooNE framework. (If you need software compiled on a 32-bit system, you can request access to this server.)
</li>
<li>Any system that is not part of the physics-analysis portion of the Nevis [[Linux cluster]]; e.g., the mail server.
</li>
<li>The systems in the Nevis [[Annex]], since they are not part of the [[condor]] batch system nor are they used to run physics software.
</li>
<li>The following systems, as of Jul-2010, have processors that are 32-bit-only:

 | *machine* | *room* | *purpose* |
 | anna | 106 | Mikhail Lelthouk's desktop |
 | claremont | 116 | Matt Toup's desktop |
 | cordwainer | 119 | scanner workstation |
 | guinevere | 117 | general student workstation |
 | harry | 117 | general student workstation |
 | hermione | 117 | general student workstation |
 | isolde | 117 | general student workstation |
 | luigi | 120 | Neutrino workstation |
 | mario | 120 | Neutrino workstation |
 | qin | 117 | general student workstation |
 | ron | 117 | general student workstation |
 | toad | 120 | Neutrino workstation |
 | yoshi | 120 | Neutrino workstation |
</li>
</ul>

---++ Why the upgrade?

Here are the reasons:

   * A number of groups are make the move to 64-bit computing:
      * The ATLAS analysis software will run on a 64-bit environment.
      * The Double Chooz group is or will be moving to a 64-bit operating system.
      * The VERITAS group's software functions best in a 64-bit environment.

   * The DOE group already runs their software in a 64-bit environment at BNL, so the change means little to them.

   * In general, a 64-bit operating system can be up to 40% faster than the equivalent 32-bit system running on the same hardware.

   * The last two weeks of August have usually been the time for upgrades to the Nevis computer cluster. In 2009, it was the shift to [[August2009SystemUpgrades][Scientific Linux 5]].

It boils down to: We would have to make the change someday, and now is as good a time as any.

---++ Which version of Linux?

[[https://www.scientificlinux.org/distributions/5x/55/][Scientific Linux 5.5]]

---++ What about existing software?

As far as the [[https://www.scientificlinux.org/][Scientific Linux]] packages are concerned, there are 64-bit versions of all existing software. The upgrade will be automatic.

If you type the command =setup= on any system on the Nevis [[Linux cluster]], you'll see that I've prepared 64-bit versions of ROOT, Geant4, CLHEP, and the GCC 4.4 compiler. Scientific Linux 5 comes with the GCC 4.1 compiler. 

The 32-bit versions of all software, both Linux- and HEP-related, will remain on the systems for as long as anyone still needs them. In particular, the GCC 3.2 compiler will remain available in a 32-bit version.

---++ What do I have to change in my scripts?

If you are moving to 64-bit versions of your programs, and you use =/usr/lib= explicitly in your scripts, you'll probably have to change it to =/usr/lib64=.

If you want to keep using the 32-bit versions of your programs and the software, you'll probably have to add =-m32= as a compiler option; e.g., =g++ -m32 myprog.cxx -o myprog=

In general, [[condor]] will only allow jobs submitted from 32-bit systems to run on 32-bit systems, and the same for 64-bit systems. You probably won't have to change any of your existing condor command files.
Topic revision: r5 - 2010-07-28 - WilliamSeligman
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