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  • Sharing Large Database Backup Among Team

    - by MattGWagner
    I work on a team of three - five developers that work on an ASP.net web application remotely. We currently run a full local database from a recent backup on all of our machines during development. The current backup, compressed, is about 18 GB. I'm looking to see if there's an easier way to keep all of our local copies relatively fresh without each of us individually downloading the 18 GB file over HTTP from our web server on a regular basis. I guess FTP is an option, but it won't speed the process up at all. I'm familiar with torrents and the thought keeps hitting me that something like that would be effective, but I'm unsure of the security or the process.

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  • How do I stop the natd log spam on Mac OS X with Internet Sharing?

    - by pukku
    Hi! I have InternetSharing enabled on my Mac (Leopard), so that my iPhone can get access to the internet in a wireless environment. Every second or so, I get the following error sent to system.log: 7/2/09 2:12:33 PM natd[20861] failed to write packet back (No route to host) Sometimes, the error is 7/2/09 2:12:33 PM natd[20861] failed to write packet back (Host is down) Is there some way to either fix the problem that is causing these errors (which I'm guessing is because the iPhone doesn't maintain a wireless connection when not in use) or to prevent them from being logged? Thanks, Ricky

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  • Iptables and counters

    - by mehturt
    I'm trying to use iptables counters with munin to monitor traffic of hosts on my local subnet. For each host I set up a rule like this: iptables -I OUTPUT -d $ip This should count the packets going from firewall to $ip, correct? I found out that this does not seem to count all packets. I start tcpdump on my router (Linux) and I see packets to $ip that are not counted. For example I check number of packets for rule to my phone IP. I start tcpdump, refresh Gmail on my phoone, I see packets in tcpdump's output but iptables rule counters are not incremented. Then I open a web page on the same phone and the counters are incremented. What could be the reason?

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  • Ubuntu 12.04 tilts when trying to open large excel file with libreoffice or matlab

    - by user1565754
    I have an xlsx-file of size 27.3MB and when I try to open it either in Libreoffice or Matlab the whole system slows down My processor is AMD Sempron(tm) 140 Processor (should be about 2.7Ghz) Memory I have about 1.7GB Any ideas? I opened this file in Windows no problem...of course it took a few seconds to load but Ubuntu freezes with this file completely...smaller files of size 3MB, 5MB etc open just fine... thnx for support =)

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  • Matlab: Optimization by perturbing variable

    - by S_H
    My main script contains following code: %# Grid and model parameters nModel=50; nModel_want=1; nI_grid1=5; Nth=1; nRow.Scale1=5; nCol.Scale1=5; nRow.Scale2=5^2; nCol.Scale2=5^2; theta = 90; % degrees a_minor = 2; % range along minor direction a_major = 5; % range along major direction sill = var(reshape(Deff_matrix_NthModel,nCell.Scale1,1)); % variance of the coarse data matrix of size nRow.Scale1 X nCol.Scale1 %# Covariance computation % Scale 1 for ihRow = 1:nRow.Scale1 for ihCol = 1:nCol.Scale1 [cov.Scale1(ihRow,ihCol),heff.Scale1(ihRow,ihCol)] = general_CovModel(theta, ihCol, ihRow, a_minor, a_major, sill, 'Exp'); end end % Scale 2 for ihRow = 1:nRow.Scale2 for ihCol = 1:nCol.Scale2 [cov.Scale2(ihRow,ihCol),heff.Scale2(ihRow,ihCol)] = general_CovModel(theta, ihCol/(nCol.Scale2/nCol.Scale1), ihRow/(nRow.Scale2/nRow.Scale1), a_minor, a_major, sill/(nRow.Scale2*nCol.Scale2), 'Exp'); end end %# Scale-up of fine scale values by averaging [covAvg.Scale2,var_covAvg.Scale2,varNorm_covAvg.Scale2] = general_AverageProperty(nRow.Scale2/nRow.Scale1,nCol.Scale2/nCol.Scale1,1,nRow.Scale1,nCol.Scale1,1,cov.Scale2,1); I am using two functions, general_CovModel() and general_AverageProperty(), in my main script which are given as following: function [cov,h_eff] = general_CovModel(theta, hx, hy, a_minor, a_major, sill, mod_type) % mod_type should be in strings angle_rad = theta*(pi/180); % theta in degrees, angle_rad in radians R_theta = [sin(angle_rad) cos(angle_rad); -cos(angle_rad) sin(angle_rad)]; h = [hx; hy]; lambda = a_minor/a_major; D_lambda = [lambda 0; 0 1]; h_2prime = D_lambda*R_theta*h; h_eff = sqrt((h_2prime(1)^2)+(h_2prime(2)^2)); if strcmp(mod_type,'Sph')==1 || strcmp(mod_type,'sph') ==1 if h_eff<=a cov = sill - sill.*(1.5*(h_eff/a_minor)-0.5*((h_eff/a_minor)^3)); else cov = sill; end elseif strcmp(mod_type,'Exp')==1 || strcmp(mod_type,'exp') ==1 cov = sill-(sill.*(1-exp(-(3*h_eff)/a_minor))); elseif strcmp(mod_type,'Gauss')==1 || strcmp(mod_type,'gauss') ==1 cov = sill-(sill.*(1-exp(-((3*h_eff)^2/(a_minor^2))))); end and function [PropertyAvg,variance_PropertyAvg,NormVariance_PropertyAvg]=... general_AverageProperty(blocksize_row,blocksize_col,blocksize_t,... nUpscaledRow,nUpscaledCol,nUpscaledT,PropertyArray,omega) % This function computes average of a property and variance of that averaged % property using power averaging PropertyAvg=zeros(nUpscaledRow,nUpscaledCol,nUpscaledT); %# Average of property for k=1:nUpscaledT, for j=1:nUpscaledCol, for i=1:nUpscaledRow, sum=0; for a=1:blocksize_row, for b=1:blocksize_col, for c=1:blocksize_t, sum=sum+(PropertyArray((i-1)*blocksize_row+a,(j-1)*blocksize_col+b,(k-1)*blocksize_t+c).^omega); % add all the property values in 'blocksize_x','blocksize_y','blocksize_t' to one variable end end end PropertyAvg(i,j,k)=(sum/(blocksize_row*blocksize_col*blocksize_t)).^(1/omega); % take average of the summed property end end end %# Variance of averageed property variance_PropertyAvg=var(reshape(PropertyAvg,... nUpscaledRow*nUpscaledCol*nUpscaledT,1),1,1); %# Normalized variance of averageed property NormVariance_PropertyAvg=variance_PropertyAvg./(var(reshape(... PropertyArray,numel(PropertyArray),1),1,1)); Question: Using Matlab, I would like to optimize covAvg.Scale2 such that it matches closely with cov.Scale1 by perturbing/varying any (or all) of the following variables 1) a_minor 2) a_major 3) theta Thanks.

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  • Why might the Large Object Heap grow rather than throw an exception?

    - by Unsliced
    In a previous question I asked possible programatic ways of maximising the largest block allocatable on the LOH. I'm still seeing the problems, but now I'm trying to get my head around why the LOH seems to grow and shrink in size, yet I'm still seeing OutOfMemoryExceptions that tally with what others have reported as being due to LOH fragmentation. Why might one call to, for example, StringBuilder.EnsureCapacity throw an OutOfMemoryException for me, but another call from somewhere else result in the LOH expanding in size (according to the performance counters, it is growing and shrinking)?

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  • How do BitTorrents connect with eachother?

    - by mazzzzz
    Hey guys, I was just downloading a new distro of linux using uTorrent, and started to wonder how uTorrent (and other bittorrents) send files to eachother through NAT routers? They obviously use the trackers to get introduced, but how do they pass info to eachother? Is there a whitepaper on this? I couldn't find one :/ Thanks, Max

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  • method to find my UDP socket's "real" port?

    - by yairchu
    Is there any free service to which I could send a UDP packet and it would respond telling me what is my "real" UDP port? (my application is behind a NAT) This kind of service could allow me to make a p2p coordination server with normal php hosting. The p2p clients would know their UDP ports from this service They will then contact my server over HTTP (which is what regular web hosting allows) and tell it their port (and ip, which is normally supplied to cgi scripts) My server will give the clients the IP addresses and ports of the other clients.

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  • How do I get the file size of a large (> 4 GB) file?

    - by endeavormac
    How can I get the file size of a file in C when the file size is greater than 4gb? ftell returns a 4 byte signed long, limiting it to two bytes. stat has a variable of type off_t which is also 4 bytes (not sure of sign), so at most it can tell me the size of a 4gb file. What if the file is larger than 4 gb?

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  • Problem with large number of markers on the map...

    - by bobetko
    I am working on an Android app that already exists on iPhone. In the app, there is a Map activity that has (I counted) around 800 markers in four groups marked by drawable in four different colors. Each group can be turned on or off. Information about markers I have inside List. I create a mapOverlay for each group, then I attach that overlay to the map. I strongly believe that coding part I did properly. But I will attach my code anyway... The thing is, my Nexus One can't handle map with all those markers. It takes around 15 seconds just to draw 500 markers. Then when all drawn, map is not quite smooth. It is sort of hard to zoom and navigate around. It can be done, but experience is bad and I would like to see if something can be done there. iPhone seems doesn't have problems showing all these markers. It takes roughly about 1-2 seconds to show all of them and zooming and panning is not that bad. Slow down is noticeable but still acceptable. I personally think it is no good to draw all those markers, but app is designed by somebody else and I am not supposed to make any drastic changes. I am not sure what to do here. It seems I will have to come up with different functionality, maybe use GPS location, if known, and draw only markers within some radius, or, if location not known, use center of the screen(map) and draw markers around that. I will have to have reasonable explanation for my bosses in case I make these changes. I appreciate if anybody has any idas. And the code: ... for (int m = 0; m < ArrList.size(); m++) { tName = ArrList.get(m).get("name").toString(); tId = ArrList.get(m).get("id").toString(); tLat = ArrList.get(m).get("lat").toString();; tLng = ArrList.get(m).get("lng").toString();; try { lat = Double.parseDouble(tLat); lng = Double.parseDouble(tLng); p1 = new GeoPoint( (int) (lat * 1E6), (int) (lng * 1E6)); OverlayItem overlayitem = new OverlayItem(p1, tName, tId); itemizedoverlay.addOverlay(overlayitem); } catch (NumberFormatException e) { Log.d(TAG, "NumberFormatException" + e); } } mapOverlays.add(itemizedoverlay); mapView.postInvalidate(); ................................ public class HelloItemizedOverlay extends ItemizedOverlay<OverlayItem> { private ArrayList<OverlayItem> mOverlays = new ArrayList<OverlayItem>(); private Context mContext; public HelloItemizedOverlay(Drawable defaultMarker, Context context) { super(boundCenterBottom(defaultMarker)); mContext = context; } public void addOverlay(OverlayItem overlay) { mOverlays.add(overlay); populate(); } @Override protected OverlayItem createItem(int i) { return mOverlays.get(i); } @Override public int size() { return mOverlays.size(); } @Override protected boolean onTap(int index) { final OverlayItem item = mOverlays.get(index); ... EACH MARKER WILL HAVE ONCLICK EVENT THAT WILL PRODUCE CLICABLE ... BALOON WITH MARKER'S NAME. return true; } }

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  • Reading from a very large table using multiple threads (Java ) and writing them to a single file

    - by user2534926
    I am currently facing a situation where i have a table with almost 80 millions data and i have to take a dump of that table and store it into a csv file. Currently i am using a not so professional approach( with a perl script+DBI interface , printing the values to stdout and redirecting to a csv file). Now i am planning to use java threading approach. Can you suggest a way forward. Thanks in advance

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  • iPhone multi-touch scale and rotate, how to prevent scale?

    - by russhill
    I have existing code for tracking multi-touch positions and then rotating and scaling the item - in this case an image - appropriately. The code works really well and in itself is perfect, however for this particular task, I need the rotation ONLY. I have spent time trying to work out what is going on in this routine, but maths is not my strong point so wanted to see if anyone could assist? - (CGAffineTransform)incrementalTransformWithTouches:(NSSet *)touches { NSArray *sortedTouches = [[touches allObjects] sortedArrayUsingSelector:@selector(compareAddress:)]; NSInteger numTouches = [sortedTouches count]; // No touches if (numTouches == 0) { return CGAffineTransformIdentity; } // Single touch if (numTouches == 1) { UITouch *touch = [sortedTouches objectAtIndex:0]; CGPoint beginPoint = *(CGPoint *)CFDictionaryGetValue(touchBeginPoints, touch); CGPoint currentPoint = [touch locationInView:self.superview]; return CGAffineTransformMakeTranslation(currentPoint.x - beginPoint.x, currentPoint.y - beginPoint.y); } // If two or more touches, go with the first two (sorted by address) UITouch *touch1 = [sortedTouches objectAtIndex:0]; UITouch *touch2 = [sortedTouches objectAtIndex:1]; CGPoint beginPoint1 = *(CGPoint *)CFDictionaryGetValue(touchBeginPoints, touch1); CGPoint currentPoint1 = [touch1 locationInView:self.superview]; CGPoint beginPoint2 = *(CGPoint *)CFDictionaryGetValue(touchBeginPoints, touch2); CGPoint currentPoint2 = [touch2 locationInView:self.superview]; double layerX = self.center.x; double layerY = self.center.y; double x1 = beginPoint1.x - layerX; double y1 = beginPoint1.y - layerY; double x2 = beginPoint2.x - layerX; double y2 = beginPoint2.y - layerY; double x3 = currentPoint1.x - layerX; double y3 = currentPoint1.y - layerY; double x4 = currentPoint2.x - layerX; double y4 = currentPoint2.y - layerY; // Solve the system: // [a b t1, -b a t2, 0 0 1] * [x1, y1, 1] = [x3, y3, 1] // [a b t1, -b a t2, 0 0 1] * [x2, y2, 1] = [x4, y4, 1] double D = (y1-y2)*(y1-y2) + (x1-x2)*(x1-x2); if (D < 0.1) { return CGAffineTransformMakeTranslation(x3-x1, y3-y1); } double a = (y1-y2)*(y3-y4) + (x1-x2)*(x3-x4); double b = (y1-y2)*(x3-x4) - (x1-x2)*(y3-y4); double tx = (y1*x2 - x1*y2)*(y4-y3) - (x1*x2 + y1*y2)*(x3+x4) + x3*(y2*y2 + x2*x2) + x4*(y1*y1 + x1*x1); double ty = (x1*x2 + y1*y2)*(-y4-y3) + (y1*x2 - x1*y2)*(x3-x4) + y3*(y2*y2 + x2*x2) + y4*(y1*y1 + x1*x1); return CGAffineTransformMake(a/D, -b/D, b/D, a/D, tx/D, ty/D); } I have tried to read up on the way matrix's work, but cannot figure it out entirely. More likely to be the issue is the calculations, which as I mention is not my strong point. What I need from this routine is a transform that performs my rotation but ignores scale - so the distance between the 2 finger touch points is ignored and scale is not affected. I have looked at other routines on the internet to handle multi-touch rotation but all the ones I tried had issues in some way or other, whereas the above code is spot on for scale and rotate actions. Any help appreciated!

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  • iPhone multi-touch move, scale and rotate, how to prevent scale?

    - by russhill
    I have existing code for tracking multi-touch positions and then moving, rotating and scaling the item - in this case an image - appropriately. The code works really well and in itself is perfect, however for this particular task, I need the movement and rotation ONLY. I have spent time trying to work out what is going on in this routine, but maths is not my strong point so wanted to see if anyone could assist? - (CGAffineTransform)incrementalTransformWithTouches:(NSSet *)touches { NSArray *sortedTouches = [[touches allObjects] sortedArrayUsingSelector:@selector(compareAddress:)]; NSInteger numTouches = [sortedTouches count]; // No touches if (numTouches == 0) { return CGAffineTransformIdentity; } // Single touch if (numTouches == 1) { UITouch *touch = [sortedTouches objectAtIndex:0]; CGPoint beginPoint = *(CGPoint *)CFDictionaryGetValue(touchBeginPoints, touch); CGPoint currentPoint = [touch locationInView:self.superview]; return CGAffineTransformMakeTranslation(currentPoint.x - beginPoint.x, currentPoint.y - beginPoint.y); } // If two or more touches, go with the first two (sorted by address) UITouch *touch1 = [sortedTouches objectAtIndex:0]; UITouch *touch2 = [sortedTouches objectAtIndex:1]; CGPoint beginPoint1 = *(CGPoint *)CFDictionaryGetValue(touchBeginPoints, touch1); CGPoint currentPoint1 = [touch1 locationInView:self.superview]; CGPoint beginPoint2 = *(CGPoint *)CFDictionaryGetValue(touchBeginPoints, touch2); CGPoint currentPoint2 = [touch2 locationInView:self.superview]; double layerX = self.center.x; double layerY = self.center.y; double x1 = beginPoint1.x - layerX; double y1 = beginPoint1.y - layerY; double x2 = beginPoint2.x - layerX; double y2 = beginPoint2.y - layerY; double x3 = currentPoint1.x - layerX; double y3 = currentPoint1.y - layerY; double x4 = currentPoint2.x - layerX; double y4 = currentPoint2.y - layerY; // Solve the system: // [a b t1, -b a t2, 0 0 1] * [x1, y1, 1] = [x3, y3, 1] // [a b t1, -b a t2, 0 0 1] * [x2, y2, 1] = [x4, y4, 1] double D = (y1-y2)*(y1-y2) + (x1-x2)*(x1-x2); if (D < 0.1) { return CGAffineTransformMakeTranslation(x3-x1, y3-y1); } double a = (y1-y2)*(y3-y4) + (x1-x2)*(x3-x4); double b = (y1-y2)*(x3-x4) - (x1-x2)*(y3-y4); double tx = (y1*x2 - x1*y2)*(y4-y3) - (x1*x2 + y1*y2)*(x3+x4) + x3*(y2*y2 + x2*x2) + x4*(y1*y1 + x1*x1); double ty = (x1*x2 + y1*y2)*(-y4-y3) + (y1*x2 - x1*y2)*(x3-x4) + y3*(y2*y2 + x2*x2) + y4*(y1*y1 + x1*x1); return CGAffineTransformMake(a/D, -b/D, b/D, a/D, tx/D, ty/D); } I have tried to read up on the way matrix's work, but cannot figure it out entirely. More likely to be the issue is the calculations, which as I mention is not my strong point. What I need from this routine is a transform that performs my movement and rotation but ignores scale - so the distance between the 2 finger touch points is ignored and scale is not affected. I have looked at other routines on the internet to handle multi-touch rotation but all the ones I tried had issues in some way or other (smoothness, jumping when lifting fingers etc), whereas the above code is spot on for move, scale and rotate actions. Any help appreciated!

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  • How can I scale an OSMF player in ActionScript 3/Flex

    - by Greg Hinch
    I am trying to create a simple video player SWF using the open source media framework in Flex 4. I want to make it dynamically scale based on the dimensions of the video, input by the user. I am following the directions on the Adobe help site, but the video does not seem to scale properly. Depending on the size, sometimes videos play larger than the space allotted on the webpage, and sometimes smaller. The only way I have been able to get it to work properly is by including a SWF metadata tag hardcoding the width and height, but I can't use that if I want to make the player dynamically sized. My code is : package { import flash.display.Sprite; import flash.events.Event; import org.osmf.media.MediaElement; import org.osmf.media.MediaPlayer; import org.osmf.media.URLResource; import org.osmf.containers.MediaContainer; import org.osmf.elements.VideoElement; import org.osmf.layout.LayoutMetadata; public class GalleryVideoPlayer extends Sprite { private var videoElement:VideoElement; private var mediaPlayer:MediaPlayer; private var mediaContainer:MediaContainer; private var flashVars:Object; public function GalleryVideoPlayer() { if (stage) init(); else addEventListener(Event.ADDED_TO_STAGE, init); } private function init(e:Event = null):void { removeEventListener(Event.ADDED_TO_STAGE, init); flashVars = loaderInfo.parameters; mediaPlayer = new MediaPlayer(); videoElement = new VideoElement(new URLResource(flashVars.file)); mediaContainer = new MediaContainer(); var layoutMetadata:LayoutMetadata = new LayoutMetadata(); layoutMetadata.width = Number(flashVars.width); layoutMetadata.height = Number(flashVars.height); videoElement.addMetadata(LayoutMetadata.LAYOUT_NAMESPACE, layoutMetadata); mediaPlayer.media = videoElement; mediaContainer.addMediaElement(videoElement); addChild(mediaContainer); } }}

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  • Event feed implementation - will it scale?

    - by SlappyTheFish
    Situation: I am currently designing a feed system for a social website whereby each user has a feed of their friends' activities. I have two possible methods how to generate the feeds and I would like to ask which is best in terms of ability to scale. Events from all users are collected in one central database table, event_log. Users are paired as friends in the table friends. The RDBMS we are using is MySQL. Standard method: When a user requests their feed page, the system generates the feed by inner joining event_log with friends. The result is then cached and set to timeout after 5 minutes. Scaling is achieved by varying this timeout. Hypothesised method: A task runs in the background and for each new, unprocessed item in event_log, it creates entries in the database table user_feed pairing that event with all of the users who are friends with the user who initiated the event. One table row pairs one event with one user. The problems with the standard method are well known – what if a lot of people's caches expire at the same time? The solution also does not scale well – the brief is for feeds to update as close to real-time as possible The hypothesised solution in my eyes seems much better; all processing is done offline so no user waits for a page to generate and there are no joins so database tables can be sharded across physical machines. However, if a user has 100,000 friends and creates 20 events in one session, then that results in inserting 2,000,000 rows into the database. Question: The question boils down to two points: Is this worst-case scenario mentioned above problematic, i.e. does table size have an impact on MySQL performance and are there any issues with this mass inserting of data for each event? Is there anything else I have missed?

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  • Diff 2 large XML files to produce a delta xml file

    - by aniln
    Need to be able to diff 2 large / very large XML files and produce the delta XML file. Also, as this process will be part of a larger automated process on below hardware / OS config. Machine hardware: sun4v OS version: 5.10 Processor type: sparc Hardware: SUNW,SPARC-Enterprise-T5220 Please let me know if there's an installable application on Solaris which can be called as part of a ksh script Example: Run driver_script.ksh Above script will have a line: xml_delta file1.xml file2.xml delta_file.xml where xml_delta is the installable application which produces the delta file after comparing file1.xml and file2.xml

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  • Proxy arp and 1:1 NAT

    - by daniel4er
    I have a Linux router with 2 NICs doing masquerade from network 192.168.0.0/24 to an ADSL router. users <----> NIC A [router] NIC B <----> INTERNET Now I'm experimenting with proxy arp on the NIC A to intercept all the IP requests in the network. I have a pool of addresses in the 192.168.0.0/24 network for this users. How can I translate, saythe IP10.0.0.64to192.168.0.64` in order to grant it internet access? I have already tried SNAT - DNAT, even I have written a NFQUEUE app to spoof the IP address with no luck.

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  • Multiple public IPs through DD-WRT without 1-to-1 NAT

    - by Stephen Touset
    I've done a search here and wasn't able to find anything relevant to my situation. I apologize in advance if I've missed an existing post on the topic. Our ISP has provided us with 6 static IP addresses. We are currently using two of them (plus one for the Comcast-provided router). One of the static addresses routes to our internal network, and the other goes to our VOIP phone system. Unfortunately, the Comcast machine doesn't support QoS, so our VOIP calls have been choppy. We plan to put the Comcast-provided router into bridge mode and replace it with an ASUS RT-N16 running DD-WRT. However, I'm unsure how to set up DD-WRT to function similarly to our existing Comcast router. The Comcast router's WAN IP is the first of our static IP addresses. We did not need to provide an internal LAN IP address — simply connecting machines that use our other public addresses to the LAN ports on the Comcast router is enough for it to route between the connected machines and our internet connection. Is there a way to do a similar setup through the DD-WRT? Thanks in advance.

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  • Good text editors or viewers for large log files

    - by Kristopher Johnson
    Log files and other textual data files are often tens or hundreds of megabytes in size, and some editors choke when you try to open something so large. What are some good applications for viewing large files? Bonus points for apps that can open compressed files, search for things with regular expressions, parse output lines, etc.

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  • Linux RAID-0 performance doesn't scale up over 1 GB/s

    - by wazoox
    I have trouble getting the max throughput out of my setup. The hardware is as follow : dual Quad-Core AMD Opteron(tm) Processor 2376 16 GB DDR2 ECC RAM dual Adaptec 52245 RAID controllers 48 1 TB SATA drives set up as 2 RAID-6 arrays (256KB stripe) + spares. Software : Plain vanilla 2.6.32.25 kernel, compiled for AMD-64, optimized for NUMA; Debian Lenny userland. benchmarks run : disktest, bonnie++, dd, etc. All give the same results. No discrepancy here. io scheduler used : noop. Yeah, no trick here. Up until now I basically assumed that striping (RAID 0) several physical devices should augment performance roughly linearly. However this is not the case here : each RAID array achieves about 780 MB/s write, sustained, and 1 GB/s read, sustained. writing to both RAID arrays simultaneously with two different processes gives 750 + 750 MB/s, and reading from both gives 1 + 1 GB/s. however when I stripe both arrays together, using either mdadm or lvm, the performance is about 850 MB/s writing and 1.4 GB/s reading. at least 30% less than expected! running two parallel writer or reader processes against the striped arrays doesn't enhance the figures, in fact it degrades performance even further. So what's happening here? Basically I ruled out bus or memory contention, because when I run dd on both drives simultaneously, aggregate write speed actually reach 1.5 GB/s and reading speed tops 2 GB/s. So it's not the PCIe bus. I suppose it's not the RAM. It's not the filesystem, because I get exactly the same numbers benchmarking against the raw device or using XFS. And I also get exactly the same performance using either LVM striping and md striping. What's wrong? What's preventing a process from going up to the max possible throughput? Is Linux striping defective? What other tests could I run?

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  • Use Excel Color Scale Formatting with Text

    - by stumpylog
    I use Excel sheets to track the status of tasks through a set of discrete statuses. I'd like to be able to format these automatically, with the start being red, the end being green and progressing through the combination colors in the middle. Status1 (Red) Status2 (More Red than Green) Status3 (More Green than Red) Status4 (Green) The "Color Scales" option under Conditional Formatting seems like it could be made to work, but it wants numbers. So, my question, can it be done? Using conditional formatting or other formulas to achieve the desired affect?

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