- Roundtable - muug.ca

NFSv4 locking problem
by Trevor Cordes 30 Mar '12

30 Mar '12

A recent update (kernel, or something else) seems to have messed up file locking over NFSv4 on my system (yes, v4 allows for locking). I use locking in perl scripts over NFS and it's always worked until now. I checked and lockd is running on the server still. A test case is at the bottom of this email. The problem hits on line 13 where the open-for-write happens. It dies with "Input/output error". The client's /v/l/messages says: [156474.509107] nfs4_reclaim_open_state: Lock reclaim failed! If I run this on a local file, not over NFS, it works fine. I'm using the lock functions as the sample code in the perl docs instructs. My goal is to lock a file, read it, do things, and write it out, all atomically. Mostly I want to protect against another instance of the same program doing the same thing at the same time and screwing up the file. My NFS server is a an older linux (Fedora 14) than the client (Fedora 16), but the NFSv4 spec hasn't really changed in that span. #!/usr/bin/perl -w # use Fcntl ':flock'; $file='/data/Tmp/locktest'; open(LOCK,$file) or die; flock(LOCK,LOCK_EX); open(IN,$file) or die; # read from file close(IN); open(ORI,">$file") or die $!; # dies here!!!!!!!!!!!!1 # write to file close(ORI); flock(LOCK,LOCK_UN);

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UG News - Register Today: Unraveling the Mobile Web, Mobile Omnivore, jQuery Mobile API In-Depth, and More
by Gilbert E. Detillieux 26 Mar '12

26 Mar '12

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UG News: Save 50% on Netduino, Arduino, and Robotics Titles. One Week Only
by Gilbert E. Detillieux 22 Mar '12

22 Mar '12

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Skullspace Hackathon this Saturday
by Colin Stanners 16 Mar '12

16 Mar '12

Hi MUUG, For any of you that didn't know, Skullspace is having its monthly hackathon this Saturday - we have a number of interesting speakers lined up, and members will be working on fun projects. More info is at http://www.skullspace.ca/wiki/index.php/Hackathon_march2012 . Thanks, -C

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Fun facts about Amazon EC2
by Kevin McGregor 14 Mar '12

14 Mar '12

Following on last night's presentation: How many blades does Amazon have? How many racks? http://huanliu.wordpress.com/2012/03/13/amazon-data-center-size/

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UG News: Last Chance to Register - Webbots & Spiders, Mobile Interface Design, PHP & Couchbase, and More
by Gilbert E. Detillieux 12 Mar '12

12 Mar '12

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MUUG Meeting, Mar 13, 7:30pm -- The Cloud
by gedetil＠cs.umanitoba.ca 06 Mar '12

06 Mar '12

The Manitoba UNIX User Group (MUUG) will be holding its next monthly meeting on Tuesday, March 13. The meeting topic for this month is as follows: The Cloud: The catchphrase of the last year, and two years to come. The basics. Everyone by now has heard of "The Cloud." Most people, even in the IT industry, are baffled as to what the cloud actually is. This no-frills, down-to-earth presentation by Rob Keizer will be on what it is, what its uses are, and the basics of setting up a private one. March's RTFM will feature the sort(1) and uniq(1) commands, presented by Brad Vokey. The group holds its general meetings at 7:30pm on the second Tuesday of every month from September to June. (There are no meetings in July and August.) Meetings are open to the general public; you don't have to be a MUUG member to attend. ********************************************************************** Please note our meeting location: The IBM offices, at 400 Ellice Ave. (between Edmonton and Kennedy). When you arrive, you will have to sign in at the reception desk, and then wait for someone to take you (in groups) to the meeting room. Please try to arrive by about 7:15pm, so the meeting can start promptly at 7:30pm. Don't be late, or you may not get in. (But don't come too early either, since security may not be there to let you in before 7:15 or so.) Non-members may be required to show photo ID at the security desk. Limited parking is available for free on the street, either on Ellice Ave. or on some of the intersecting streets. Indoor parking is also available nearby, at Portage Place, for $5.00 for the evening. Bicycle parking is available in a bike rack under video surveillance located behind the building on Webb Place. ********************************************************************** For more information about MUUG, and its monthly meetings, check out their Web server: http://www.muug.mb.ca/ Help us promote this month's meeting, by putting this poster up on your workplace bulletin board or other suitable public message board: http://www.muug.mb.ca/meetings/MUUGmeeting.pdf -- Gilbert E. Detillieux E-mail: <gedetil(a)muug.mb.ca> Manitoba UNIX User Group Web: http://www.muug.mb.ca/ PO Box 130 St-Boniface Phone: (204)474-8161 Winnipeg MB CANADA R2H 3B4 Fax: (204)474-7609

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UG News: Last Chance - JQuery Mobile, Meaningful SEO Metrics, and More
by Gilbert E. Detillieux 05 Mar '12

05 Mar '12

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Re: [RndTbl] ZFS I/O strangeness
by Adam Thompson 03 Mar '12

03 Mar '12

I get the best performance out of dd(1) at 8MB block size, but it's still less than if I cat and pipe. It's standard GNU cat, which does not do anything fancy like that AFAIK. Possibly Solaris has enormous pipelines, and has wildly optimized multi-processor I/O, so two processes are faster than one?? -Adam Gilles Detillieux <grdetil(a)scrc.umanitoba.ca> wrote: >I'd expect the readahead to be the same for the two commands, as it >should all happen behind the scenes at the filesystem level. Or does >the C library, or the cat command itself, do its own readahead? More >likely cat is using a different input buffer size than 8k and that is >resulting in the extra efficiency. I'd try different bs= values on the >first dd command to see if that helps. > >On 03/03/2012 12:52 PM, Adam Thompson wrote: >> I have a ZFS RAIDZ3 filesystem under OpenSolaris (actually a Nexenta build >> so a GNU userland on top of OpenSolaris kernel). >> >> "dd if=filename of=/dev/null bs=8k" gives me ~66Mbytes/sec. >> "cat filename | dd of=/dev/null bs=8k" gives me ~142Mbytes/sec. >> >> WTF? Why would using cat *increase* the overall speed? >> The only thing I can think of is readahead, but why would cat cause that >> to happen while dd doesn't? >> >> -Adam Thompson >> athompso(a)athompso.net >> >> >> >> _______________________________________________ >> Roundtable mailing list >> Roundtable(a)muug.mb.ca >> http://www.muug.mb.ca/mailman/listinfo/roundtable > >-- >Gilles R. Detillieux E-mail:<grdetil(a)scrc.umanitoba.ca> >Spinal Cord Research Centre WWW: http://www.scrc.umanitoba.ca/ >Dept. Physiology, U. of Manitoba Winnipeg, MB R3E 0J9 (Canada) > >_______________________________________________ >Roundtable mailing list >Roundtable(a)muug.mb.ca >http://www.muug.mb.ca/mailman/listinfo/roundtable >

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Fwd: USENIX/ACM NSDR '12 Call For Papers Now Available
by Gilbert E. Detillieux 02 Mar '12

02 Mar '12

FYI... -------- Original Message -------- Subject: USENIX/ACM NSDR '12 Call For Papers Now Available Date: Fri, 2 Mar 2012 12:33:24 -0800 From: Lionel Garth Jones <lgj(a)usenix.org> On behalf of the 6th USENIX/ACM Workshop on Networked Systems for Developing Regions (NSDR '12) program committee, we invite you to submit papers that propose and discuss ideas concerning the design, implementation, and evaluation of new computing and communications technologies to support the sustainable development of developing regions. Please submit all paper titles and abstracts by March 27, 2012, 11:59 p.m. PDT. NSDR focuses on the technical networking and systems research challenges that arise in the design, implementation, and deployment of new computing solutions appropriate for developing regions. We encourage the submission of position papers or the results of preliminary work describing interesting, original, previously unpublished ideas or results pertaining to the design, implementation, and/or evaluation of networks and systems for developing regions. Areas of interest include, but are not limited to: * Low-cost wireless connectivity * Intermittent and delay-tolerant systems * Rural network planning * Spectrum management protocols and techniques * Mechanisms for emergency and urgent communications * Location-aware systems * Power-efficient systems * Low-cost computing devices * Mobile systems and applications * Middleware and mechanisms for minimizing energy, latency, and storage (caching, etc.) * Adapting content and applications for local languages * User interfaces for low-literacy populations * Shared access devices and infrastructure, including personalization and privacy concerns * Design and evaluation of applications and in-depth case studies in the areas of public health, microfinance, agriculture, e-governance, education, monitoring, disaster management, etc. Paper submissions are due Tuesday, March 27, 2012, 11:59 p.m. PDT. For more details on the submission process, please see the complete Call for Papers at: http://usenix.org/conference/nsdr12/ We look forward to receiving your submissions! Kameswari Chebrolu, Indian Institute of Technology, Bombay Brian Noble, University of Michigan USENIX NSDR '12 Program Co-Chairs nsdr12chairs(a)usenix.org --------------------------------- Call for Papers 6th USENIX/ACM Workshop on Networked Systems for Developing Regions June 15, 2012 Boston, MA http://usenix.org/conference/nsdr12 Submissions due: March 27, 2012, 11:59 p.m. PDT. Notification to authors: April 26, 2012 Electronic files of final papers due: May 14, 2012 ---------------------------------

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