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<channel>
	<title>Xor News &#187; Computers</title>
	<atom:link href="http://www.flester.com/blog/category/computers/feed" rel="self" type="application/rss+xml" />
	<link>http://www.flester.com/blog</link>
	<description>You can't have it both ways</description>
	<lastBuildDate>Sat, 30 Jul 2011 12:18:32 +0000</lastBuildDate>
	<language>en</language>
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		<title>Tandem Computers</title>
		<link>http://www.flester.com/blog/2011/02/24/tandem</link>
		<comments>http://www.flester.com/blog/2011/02/24/tandem#comments</comments>
		<pubDate>Thu, 24 Feb 2011 04:48:33 +0000</pubDate>
		<dc:creator>mike</dc:creator>
				<category><![CDATA[Computers]]></category>

		<guid isPermaLink="false">http://www.flester.com/blog/?p=389</guid>
		<description><![CDATA[Tandem Computers were the first large computer systems I worked on professionally. The Tandem Application Language (TAL) was the first full-time professional programming language I worked in. I have very fond memories of it. The combination of the language with their hardware could do some amazing things. Today we mostly do the same things with [...]]]></description>
			<content:encoded><![CDATA[<p>Tandem Computers were the first large computer systems I worked on professionally. The Tandem Application Language (TAL) was the first full-time professional programming language I worked in. I have very fond memories of it. The combination of the language with their hardware could do some amazing things. Today we mostly do the same things with racks of commodity hardware, but for the time it was pretty cool stuff. Tandem was known for fault-tolerant hardware, &#8220;dual-ported&#8221; hard drives, redundant everything, and cross-cpu checkpointing software. Back in the day, I got a fault tolerant coffee mug with the Tandem logo on it.</p>
<p>It failed yesterday. After 15 years of good service. Not bad.</p>
<div id="attachment_390" class="wp-caption aligncenter" style="width: 650px"><a href="http://www.flester.com/blog/wp-content/uploads//2011/02/tandem-mug.jpg"><img src="http://www.flester.com/blog/wp-content/uploads//2011/02/tandem-mug.jpg" alt="Tandem Mug" title="tandem-mug" width="640" height="480" class="size-full wp-image-390" /></a><p class="wp-caption-text">Tandem Mug</p></div>
<p>But since it was fault-tolerant and &#8220;dual ported&#8221; the cup of coffee was finished safely and without any catastrophic results.<br />
So long Tandem mug. It was good to know ya.</p>
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		<title>Apple FanBoi Status</title>
		<link>http://www.flester.com/blog/2010/10/23/apple-fanboi-status</link>
		<comments>http://www.flester.com/blog/2010/10/23/apple-fanboi-status#comments</comments>
		<pubDate>Sat, 23 Oct 2010 02:43:31 +0000</pubDate>
		<dc:creator>mike</dc:creator>
				<category><![CDATA[Java]]></category>
		<category><![CDATA[Mac]]></category>

		<guid isPermaLink="false">http://www.flester.com/blog/?p=345</guid>
		<description><![CDATA[Yeah. I&#8217;m an apple fanboi. Some days I wish I could quit. Herewith a status update on various aspects of fanboi-dom. 1. Macbook Pro &#8211; a late 2007 model. Hanging in there. Lost the HDD when it was 2 weeks old, replaced at their expense. Been using TimeMachine with an external after that. Lost the [...]]]></description>
			<content:encoded><![CDATA[<p>Yeah. I&#8217;m an apple fanboi. Some days I wish I could quit. Herewith<br />
a status update on various aspects of fanboi-dom.</p>
<p>1. Macbook Pro &#8211; a late 2007 model. Hanging in there. Lost the HDD when<br />
it was 2 weeks old, replaced at their expense. Been using TimeMachine<br />
with an external after that. Lost the right arrow key over the summer.<br />
Replaced at their expense. Nothing serious.</p>
<p>2. iPad &#8211; mid 2010. Not entirely useless. It is good for reading ebooks.<br />
Not much else. Not good for family sharing, email, documents, music,<br />
pictures as it can only sync with one iTunes. Not good for kids since<br />
there is no Flash (i.e. no Webkinz). No Google Chrome. No logins and<br />
passwords. No parental controls. Very disappointing.</p>
<p>3. MacPro &#8211; late 2010. 27&#8243; Cinema display died after 3 days. 2 Hours with<br />
support, rebooted about a hundred times. Sent it back, got a new one.<br />
Out of commission for six days. The display has no power button and not<br />
even a little light to indicate that it is getting power. Seems like something<br />
that should be added in a future rev. Most folks thought of that back in the<br />
&#8217;60&#8242;s.</p>
<p>4. MacOS X 10.6. Ok. The system wanted to give me a new JDK (1.6 update 2)<br />
Wednesday night. Took it. Now none of my JNI code compiles. What? There is<br />
a symlink to jni.h that points off to nowhere. Is that file optional? Did no one<br />
else ever check that a jni.h file was included in that release? Word on the street<br />
is to get the JDK 1.6 update 3 from the Apple Developer Connection. Right.<br />
It does have the jni.h file but it&#8217;s still in the WRONG PLACE APPLE! And it<br />
reports the exact same version number as update 2. Unbelievable. Update 2<br />
is unfixable, but here is how I fixed update 3</p>
<ol>
<li>cd /System/Library/Frameworks/JavaVM.framework/Versions/1.6.0/Home/</li>
<li>sudo mkdir include</li>
<li>cd include</li>
<li>for f in  /System/Library/Frameworks/JavaVM.framework/Versions/A/Headers/*.h; do sudo ln -s $f .;  done</li>
</ol>
<p>5. The MacBookPro 2007 cannot connect to the 2010 27&#8243; Cinema Display. Without buying<br />
an adapter. No mini-DVI plug on the MBP 2007 model. For the price yous guys could<br />
have included the stupid adapter.</p>
<p>6. A new version of iLife was just announced. Bummer as I just bought the update to the<br />
previous version. I wonder if they will make that right?</p>
<p>The disappointments are sort of piling up. This is no where near the tipping point for<br />
me personally, but it does start to affect how much I recommend Apple stuff. </p>
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		<title>iPad &#8211; Fail, Fail, Fail.</title>
		<link>http://www.flester.com/blog/2010/10/02/ipad-fail-fail-fail</link>
		<comments>http://www.flester.com/blog/2010/10/02/ipad-fail-fail-fail#comments</comments>
		<pubDate>Sat, 02 Oct 2010 18:42:21 +0000</pubDate>
		<dc:creator>mike</dc:creator>
				<category><![CDATA[Computers]]></category>
		<category><![CDATA[Family]]></category>

		<guid isPermaLink="false">http://www.flester.com/blog/?p=329</guid>
		<description><![CDATA[I bought an iPad. I didn&#8217;t do my homework. It took 5 minutes with the device to figure out that it won&#8217;t work for us. There are no logins and passwords. No separate accounts. That means Email? Nope. Too much caching and user switching are not compatible. Games? Nope, someone else just advanced a level [...]]]></description>
			<content:encoded><![CDATA[<p>I bought an iPad. I didn&#8217;t do my homework. It took 5 minutes<br />
with the device to figure out that it won&#8217;t work for us. </p>
<ul>
<li>There are no logins and passwords. No separate accounts.  That means
<ul>
<li>Email? Nope. Too much caching and user switching are not compatible.</li>
<li>Games? Nope, someone else just advanced a level or started over</li>
<li>Documents? Nope. Security, privacy issues.</li>
</ul>
</li>
<li>It does not run Mac OS Parental Controls</li>
<li>No Google Chrome browser</li>
<li>No Hulu. Without a 9.99 per month subscription. Zero chance of that happening.</li>
</ul>
<p>I would also put &#8220;No Emacs&#8221;, but I never expected that.</p>
<p>After looking around I think the Samsung Galaxy Tab suffers from the same<br />
fundamental issue. </p>
<p>These devices are toys, not practical for our family to use.</p>
<p>If you need an iPad cheap, let me know.</p>
]]></content:encoded>
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		<title>Best Single Line of Code Ever</title>
		<link>http://www.flester.com/blog/2010/05/29/best-single-line-of-code-ever</link>
		<comments>http://www.flester.com/blog/2010/05/29/best-single-line-of-code-ever#comments</comments>
		<pubDate>Sat, 29 May 2010 13:39:57 +0000</pubDate>
		<dc:creator>mike</dc:creator>
				<category><![CDATA[Computers]]></category>
		<category><![CDATA[Java]]></category>

		<guid isPermaLink="false">http://www.flester.com/blog/?p=288</guid>
		<description><![CDATA[Quite possibly my best single line of code ever. Certainly my best single line of Java ever. And it&#8217;s in a unit test. private static String W = "Президент Буш"; What&#8217;s yours?]]></description>
			<content:encoded><![CDATA[<p>Quite possibly my best single line of code ever. Certainly my best single line of Java ever.<br />
And it&#8217;s in a unit test.</p>
<p><code><br />
     <span style="color:#a020f0">private static</span> <span style="color:#228b22">String</span> <span style="color:#b8860b">W</span> = <span style="color:#bc8f8f">"Президент Буш"</span>;<br />
</code></p>
<p>What&#8217;s yours?</p>
]]></content:encoded>
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		<item>
		<title>User Interface Design</title>
		<link>http://www.flester.com/blog/2009/12/01/user-interface-design</link>
		<comments>http://www.flester.com/blog/2009/12/01/user-interface-design#comments</comments>
		<pubDate>Tue, 01 Dec 2009 02:30:33 +0000</pubDate>
		<dc:creator>mike</dc:creator>
				<category><![CDATA[Computers]]></category>

		<guid isPermaLink="false">http://www.flester.com/blog/?p=244</guid>
		<description><![CDATA[Here are some that are noteworthy and funny: Is it Christmas &#8211; http://isitchristmas.com &#8211; Funny as it tracks the timezones across the globe, really only has much to do on one day per year though. But that one day is coming up soon, so start checking in daily. Is it Dark Outside &#8211; http://isitdarkoutside.com &#8211; [...]]]></description>
			<content:encoded><![CDATA[<p>Here are some that are noteworthy and funny:</p>
<ul>
<li>Is it Christmas &#8211; <a href="http://isitchristmas.com/">http://isitchristmas.com</a> &#8211; Funny as it tracks the timezones across the globe, really only has much to do on one day per year though. But that one day is coming up soon, so start checking in daily.</li>
<li>Is it Dark Outside &#8211; <a href="http://isitdarkoutside.com/">http://isitdarkoutside.com</a> &#8211; Whopping funny. Works every day of the year.</li>
<li>Umbrella Today &#8211; <a href="http://umbrellatoday.com/">http://umbrellatoday.com</a> &#8211; I guess they are hawking an iPhone app, but I really enjoyed how the interface pulls you in a little bit at a time. And if you visit for the first time on a rainy day (or just put in a Seattle, Washington zip code), that rainy-day graphic is stunning.</li>
</ul>
<p>It&#8217;s all about hiding the complexity. Do something hard with your software but don&#8217;t make the users suffer just you did.</p>
]]></content:encoded>
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		<item>
		<title>Special error codes</title>
		<link>http://www.flester.com/blog/2009/10/17/special-error-codes</link>
		<comments>http://www.flester.com/blog/2009/10/17/special-error-codes#comments</comments>
		<pubDate>Sat, 17 Oct 2009 19:03:43 +0000</pubDate>
		<dc:creator>mike</dc:creator>
				<category><![CDATA[Computers]]></category>

		<guid isPermaLink="false">http://www.flester.com/blog/?p=237</guid>
		<description><![CDATA[A recent tweet from my pal #eknock complaining about some juicy ORA-06550: line 1, column 7 reminded me of these error codes that an old-cgi script of min produces: Bad disktype code ORA-99xxx CTXUSER not enabled ORA-010xxx Flagellular misfire ORA-910xxx Nascent order lost code: ORA-82xxx Ferrule injector not found: ORA-14xxx Of course it&#8217;s just a [...]]]></description>
			<content:encoded><![CDATA[<p>A recent tweet from my pal #eknock complaining about some juicy <strong>ORA-06550: line 1, column 7</strong> reminded me of these error codes that an old-cgi script of min produces:</p>
<ul>
<li>Bad disktype code ORA-99xxx</li>
<li>CTXUSER not enabled ORA-010xxx</li>
<li>Flagellular misfire ORA-910xxx</li>
<li>Nascent order lost code: ORA-82xxx</li>
<li>Ferrule injector not found: ORA-14xxx</li>
</ul>
<p>Of course it&#8217;s just a perl script and the system had nothing to do with Oracle. Just one of those little things that can be done to throw snoopers off the trail. </p>
]]></content:encoded>
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		<item>
		<title>Hadoop World 2009</title>
		<link>http://www.flester.com/blog/2009/10/04/hadoop-world-2009</link>
		<comments>http://www.flester.com/blog/2009/10/04/hadoop-world-2009#comments</comments>
		<pubDate>Sun, 04 Oct 2009 02:59:09 +0000</pubDate>
		<dc:creator>mike</dc:creator>
				<category><![CDATA[Computers]]></category>

		<guid isPermaLink="false">http://www.flester.com/blog/?p=230</guid>
		<description><![CDATA[Yesterday I attended the first-ever Hadoop World, sponsored by Cloudera and held in The Roosevelt Hotel in New York City. I took an early Amtrak train up to the big city and a late train back that same night. The conference was well attended, over 500 big-data heads were there and the organizers did a [...]]]></description>
			<content:encoded><![CDATA[<p>Yesterday I attended the first-ever <a href="http://hadoop.apache.org/">Hadoop</a> World, sponsored by <a href="http://cloudera.com/">Cloudera</a> and held in <a href="http://theroosevelthotel.com/">The Roosevelt Hotel</a> in New York City. I took an early Amtrak train up to the big city and a late train back that same night. The conference was well attended, over 500 big-data heads were there and the organizers did a fantastic job.</p>
<p>Some of the best stuff was just hearing about how other folks are using Hadoop. I also enjoyed hearing about the sizes of other people&#8217;s big-data problems. There were three tracks, so I only heard 1/3 of what took place, but here are some notes on what I did hear after the break.</p>
<p>It was a great day, a long day, glad I went.<span id="more-230"></span></p>
<h2>Yahoo and Hadoop &#8211; Eric14</h2>
<p> Yahoo search assist is now build with Hadoop based on 3 years of log data. It is a 20 step map-reduce job and it runs in about 20 minutes on their production cluster. This is down from a 26 day run (did I get that right?) in the pre-Hadoop days. Wow. Y! has several Hadoop clusters and the biggest is 4K nodes, 16Pb disk, 64 Tb RAM, 32K cores running Hadoop 18.3. Wow. I&#8217;m drooling over that. </p>
<p>Yahoo! folks are the biggest Hadoop committers and Y! sounds solidly behind the thing just like they have been since its inception. That was great to hear. Just about every zone of the Yahoo! home page has some contribution from a map-reduce job at some point.</p>
<p>Some stuff to keep an eye out for</p>
<ul>
<li>Zebra &#8211; a column oriented data store on hdfs</li>
<li>Ooozie &#8211; a workflow and scheduling piece for map-reduce</li>
<li>Mumak simulator &#8211; need to look that one up</li>
</ul>
<h2>Facebook &#8211; Ashish Thusoo</h2>
<p>Fb gets 4Tb of compressed data per day with a 6-7x compression factor. That&#8217;s a lot of data. They separate production and ad-hoc jobs on to different clusters and use hive-replication to get the data in both places. This is something that is not publicly available yet but they have plans to open-source it when it is ready. Their big cluster is 4800 cores, 5.5 Pb disk, 12Tb disk per node. They run 7500 hive jobs per day, 95% of all jobs are hive, and this cluster runs 80,000 compute hours per day. </p>
<h2>Visa &#8211; Joe Cunningham</h2>
<p>Visa has had Hadoop in their research department for about 9 months and is doing some interesting things with it.  They certainly have a big-data problem: 28 million merchants, 1.4 million ATM machines, 500 million accounts, 100-130 million transactions per day (8k per second). The Visa Net portion of a transaction approval happens in 50 ms and Visa Net has 2 seconds downtime per year.</p>
<p>Visa uses lots of FOSS in the enterprise so their interest in Hadoop came about in a perfectly natural way.  One of the things the current research does is to produce fraud models that can be used in the real-time system. These models are produced off-line and it currently takes about 1 month to generate a fully-functional model. This involves sampling data, moving data, compressing data, etc. With Hadoop a fully-functional model can be generated in 13 minutes. Lots of the research happens on synthetic data and Visa has created map jobs to generate synthetic transaction data at the rate of 2 years of synthetic transactions in 6 hours.</p>
<h2>Rackspace &#8211; Stu Hood</h2>
<p>Stu talked most about the email and app hosting division of Rackspace but there are a lot of interesting things happening in Rackspace, both in the mail hosting division and in other divisions. The mail hosting division generates a lot of logs and needs to be very proactive in finding and surfacing delivery problems and dealing with spam and malware. They generate 300Gb/day of logs and have a 6 month window for analysis. There was some interesting talk of using map-reduce to generate a Lucene intermediate index format and then using Solr to merge it up into a searchable index. The time window target is to be able to query on data within 15 minutes of the event and to query on any dimension. </p>
<p>They either are or will be using Scribe to ingest data (syslog data?) directly into HDFS. I need to look into Scribe more as I had sort of forgotten about it. It could help solve some pressing issues.</p>
<h2> JP Morgan Chase</h2>
<p>One very interesting point the speakers brought out is that once your transactional data gets to be over 1 day old it is usually entirely static. But still it sits there provisioned and protected in your enterprise RDBMS transactional data store &#8212; read only. We can do better than that!</p>
<h2>HDFS Security &#8211; Owen O&#8217;Malley, Yahoo!</h2>
<p>There is lots of work going on to secure Hadoop Namenode, Jobtracker and Datanode. This is super important to our clients too and so we are very interested in seeing this succeed. Some of the major points:</p>
<ul>
<li>Namenode will give the user a Kerberos token to access blocks on a data node</li>
<li>Only the user of a map-reduce job will be able to modify or kill it</li>
<li>Map-reduce jobs run as the user</li>
<li>Task working directory visibility limited to the user</li>
<li>Only the right reduce tasks can see teh map outputs (secure shuffle)</li>
<li>Encryption optional</li>
<li>SPNEGO = permissions everywhere</li>
</ul>
<p>In addition to the security work Owen talked some about how to make backward compatible APIs and how to mark them as such. The need for this grows as the project grows larger ecosystems. File system compatibility is also important. We know this right well as we got stuck on the bogus Hadoop 0.19 version that no one even mentions in public. We couldn&#8217;t go back to 0.18 and 0.20 wasn&#8217;t stable yet. Stuck stuck stuck.</p>
<h2>VAIDYA</h2>
<p>There are 165+ tunable parameters in Hadoop. Changing one usually has impact on the others. Vaidya uses a set of rules to analyze map-reduce history (after a job has run) using the user history and the job conf. It can measure things like reducer balance, check for compressed intermediate data, determine whether a combiner would be likely to help, and many other things. This is a lot of the stuff we do by hand when evaluating a map-reduce job. You could see something like this being used as a part of the certification that a job is ready to run on your production cluster.<a href="https://issues.apache.org/jira/browse/HADOOP-4179"> JIRA 4179</a>.</p>
<h2>eBay Streaming Architecture &#8211; Neel Sundaresan</h2>
<p>eBay users spend $1400 per second. A vehicle is sold every 2 minutes. There are about 10 million new listings per day and 250 million users. The typical item on eBay is not catalogable (is that a word?) as most items are one-of-a-kind. So as compared to a Netflix type recommender system where you might need a 100k x 100k matrix, the eBay recommender  would be an extremely large, sparse array. Neel called this a &#8220;long-tail&#8221; type system. There are terabytes of new transaction and user session data per day. eBay Research Labs studies this data to determine behavior in a number of dimensions, figures out how to perform A/B testing experiments, and  does trending analysis. </p>
<p>The streaming architecture (Mobius) has a query language (MQL) that gives an SQL like interface but adds a <b>start</b> and <b>end</b> section to the query to give the window of data to operate on. </p>
<h2>High Availability Hadoop &#8211; webContext</h2>
<p>I had some problems understanding this talk at the beginning, but warmed up to it as it went along. There were lots of interesting products and tools mentioned that I should look into more.</p>
<ul>
<li>Hotslice to monitor job exit status</li>
<li>Network bonding with LACP</li>
<li>DRBD for disk mirroring</li>
<li>Linux HA from linux-ha.org</li>
<li>Spacewalk &#8211; an open source system like RedHat Satellite server</li>
</ul>
<p>These guys have two machines running the Namenode using LinuxHA and DRBD on a virtual IP address. In addition to that they use the REST interface to the NameNode to /getimage and /getedit once per hour and make additional backups. They have had 6 NN failures in the last 18 months, 3 planned, 3 unplanned and have about a 15 second rollover to the backup. That is intense. Read more about <a href="http://www.cloudera.com/blog/2009/07/22/hadoop-ha-configuration/">this configuration</a> on the cloudera blog.</p>
<h2>RADFS</h2>
<p>This is a set of patches in progress to make a low-latency HDFS. This is important work for things like hBase. There are some huge inefficiencies in sockets, file handles, and network usage for small positioned reads. There is still a lot of work to do on these patches before it could reasonably take over for the current HDFS approach. Interesting things to think about. <a href="https://issues.apache.org/jira/browse/HDFS-516">JIRA HDFS-516</a>.</p>
<h2>Automatic Problem Diagnosis &#8211; CMU Team</h2>
<p>The CMU team is using the M45 cluster that Y! has made available to several universities. They have some really nice visualizations of problems occurring in the cluster that come from looking at 64 different metrics in collected log files. One metric I thought especially interesting was heartbeat date skew between the master and slave.  This work is being tracked in<a href="https://issues.apache.org/jira/browse/CHUKWA-94"> JIRA Chukwa &#8211; 94</a>.</p>
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		<title>WP 2.8 and 2.8.1 comments permalinks problem</title>
		<link>http://www.flester.com/blog/2009/07/11/wp-2-8-and-2-8-1-comments-permalinks-problem</link>
		<comments>http://www.flester.com/blog/2009/07/11/wp-2-8-and-2-8-1-comments-permalinks-problem#comments</comments>
		<pubDate>Sat, 11 Jul 2009 03:16:27 +0000</pubDate>
		<dc:creator>mike</dc:creator>
				<category><![CDATA[Computers]]></category>

		<guid isPermaLink="false">http://www.flester.com/blog/2009/07/11/wp-2-8-and-2-8-1-comments-permalinks-problem</guid>
		<description><![CDATA[Upgrade to WP 2.8 broke the comments permalinks, 2.8.1 didn&#8217;t help. The user would get an error page after posting a comment (comment was posted) and clicking on any of the links to a comment went to the-url-for-the-post/comments-page-1#comment-id which would get you a 404. In the admin settings discussion area there is a (new?) setting [...]]]></description>
			<content:encoded><![CDATA[<p>Upgrade to WP 2.8 broke the comments permalinks, 2.8.1 didn&#8217;t help. The user would get an error page after posting a comment (comment was posted) and clicking on any of the links to a comment went to the-url-for-the-post/comments-page-1#comment-id which would get you a 404. In the admin settings discussion area there is a (new?) setting to break comments up into pages of 50. Turning this off fixed the problem. I&#8217;ve never had 50 non-spam comments so that shouldn&#8217;t hurt too much. Plus I don&#8217;t think I ever turned it on in the first place.</p>
]]></content:encoded>
			<wfw:commentRss>http://www.flester.com/blog/2009/07/11/wp-2-8-and-2-8-1-comments-permalinks-problem/feed</wfw:commentRss>
		<slash:comments>1</slash:comments>
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		<item>
		<title>Scaling Rails Screencast</title>
		<link>http://www.flester.com/blog/2009/06/13/scaling-rails-screencast</link>
		<comments>http://www.flester.com/blog/2009/06/13/scaling-rails-screencast#comments</comments>
		<pubDate>Sat, 13 Jun 2009 16:38:41 +0000</pubDate>
		<dc:creator>mike</dc:creator>
				<category><![CDATA[Rails]]></category>

		<guid isPermaLink="false">http://www.flester.com/blog/2009/06/13/scaling-rails-screencast</guid>
		<description><![CDATA[This screen cast covers Scaling Rails apps using Rack and Metal and is an execellent tutorial on both subjects. Jason Pollack, one of the Rails Envy guys, does a superb job explaining how rack and metal work in Rails 2.3.]]></description>
			<content:encoded><![CDATA[<p>This screen cast covers <a href="http://nr-content.s3.amazonaws.com/railslab/videos/14-ScalingRails-Rack-and-Metal.mp4">Scaling Rails apps using Rack and Metal</a> and is an execellent tutorial on both subjects. Jason Pollack, one of the Rails Envy guys, does a superb job explaining how rack and metal work in Rails 2.3. </p>
]]></content:encoded>
			<wfw:commentRss>http://www.flester.com/blog/2009/06/13/scaling-rails-screencast/feed</wfw:commentRss>
		<slash:comments>0</slash:comments>
<enclosure url="http://nr-content.s3.amazonaws.com/railslab/videos/14-ScalingRails-Rack-and-Metal.mp4" length="49733893" type="video/mp4" />
		</item>
		<item>
		<title>d-Left Hashing</title>
		<link>http://www.flester.com/blog/2009/06/13/d-left-hashing</link>
		<comments>http://www.flester.com/blog/2009/06/13/d-left-hashing#comments</comments>
		<pubDate>Sat, 13 Jun 2009 02:16:30 +0000</pubDate>
		<dc:creator>mike</dc:creator>
				<category><![CDATA[Computers]]></category>

		<guid isPermaLink="false">http://www.flester.com/blog/?p=161</guid>
		<description><![CDATA[Reading an interesting paper on d-Left Hashing (pdf link) by Bonomi, Mitzenmacher, et. al. This is a space and effeciency improvement on Bloom filters. Wondering how it could be incorporated into a Hadoop mapfile to avoid scanning compressed blocks for keys that aren&#8217;t present. Maybe the work in hbase on o.a.h.hbase.io.BloomFilterMapFile would provide good clues. [...]]]></description>
			<content:encoded><![CDATA[<p>Reading an interesting paper on <a href="http://www.csl.uiuc.edu/allerton/archives/allerton06/PDFs/papers/0183.pdf">d-Left Hashing (pdf link)</a> by Bonomi, Mitzenmacher, et. al. This is a space and effeciency improvement on Bloom filters. Wondering how it could be incorporated into a <a href="http://hadoop.apache.org/core">Hadoop</a> <a href="http://hadoop.apache.org/core/docs/r0.18.3/api/org/apache/hadoop/io/MapFile.html">mapfile</a> to avoid scanning compressed blocks for keys that aren&#8217;t present. Maybe the work in hbase on o.a.h.hbase.io.BloomFilterMapFile would provide good clues. Need to understand the dynamic bit reassignment stuff first though.</p>
]]></content:encoded>
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		<slash:comments>0</slash:comments>
		</item>
	</channel>
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