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• SQL Server: Why use shorter VARCHAR(n) fields?

  - by chryss

  It is frequently advised to choose database field sizes to be as narrow as possible. I am wondering to what degree this applies to SQL Server 2005 VARCHAR columns: Storing 10-letter English words in a VARCHAR(255) field will not take up more storage than in a VARCHAR(10) field. Are there other reasons to restrict the size of VARCHAR fields to stick as closely as possible to the size of the data? I'm thinking of Performance: Is there an advantage to using a smaller n when selecting, filtering and sorting on the data? Memory, including on the application side (C++)? Style/validation: How important do you consider restricting colunm size to force non-sensical data imports to fail (such as 200-character surnames)? Anything else? Background: I help data integrators with the design of data flows into a database-backed system. They have to use an API that restricts their choice of data types. For character data, only VARCHAR(n) with n <= 255 is available; CHAR, NCHAR, NVARCHAR and TEXT are not. We're trying to lay down some "good practices" rules, and the question has come up if there is a real detriment to using VARCHAR(255) even for data where real maximum sizes will never exceed 30 bytes or so. Typical data volumes for one table are 1-10 Mio records with up to 150 attributes. Query performance (SELECT, with frequently extensive WHERE clauses) and application-side retrieval performance are paramount.

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• Why is UITableView not reloading (even on the main thread)?

  - by radesix

  I have two programs that basically do the same thing. They read an XML feed and parse the elements. The design of both programs is to use an asynchronous NSURLConnection to get the data then to spawn a new thread to handle the parsing. As batches of 5 items are parsed it calls back to the main thread to reload the UITableView. My issue is it works fine in one program, but not the other. I know that the parsing is actually occuring on the background thread and I know that [tableView reloadData] is executing on the main thread; however, it doesn't reload the table until all parsing is complete. I'm stumped. As far as I can tell... both programs are structured exactly the same way. Here is some code from the app that isn't working correctly. - (void)startConnectionWithURL:(NSString *)feedURL feedList:(NSMutableArray *)list { self.feedList = list; // Use NSURLConnection to asynchronously download the data. This means the main thread will not be blocked - the // application will remain responsive to the user. // // IMPORTANT! The main thread of the application should never be blocked! Also, avoid synchronous network access on any thread. // NSURLRequest *feedURLRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:feedURL]]; self.bloggerFeedConnection = [[[NSURLConnection alloc] initWithRequest:feedURLRequest delegate:self] autorelease]; // Test the validity of the connection object. The most likely reason for the connection object to be nil is a malformed // URL, which is a programmatic error easily detected during development. If the URL is more dynamic, then you should // implement a more flexible validation technique, and be able to both recover from errors and communicate problems // to the user in an unobtrusive manner. NSAssert(self.bloggerFeedConnection != nil, @"Failure to create URL connection."); // Start the status bar network activity indicator. We'll turn it off when the connection finishes or experiences an error. [UIApplication sharedApplication].networkActivityIndicatorVisible = YES; } - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response { self.bloggerData = [NSMutableData data]; } - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { [bloggerData appendData:data]; } - (void)connectionDidFinishLoading:(NSURLConnection *)connection { self.bloggerFeedConnection = nil; [UIApplication sharedApplication].networkActivityIndicatorVisible = NO; // Spawn a thread to fetch the link data so that the UI is not blocked while the application parses the XML data. // // IMPORTANT! - Don't access UIKit objects on secondary threads. // [NSThread detachNewThreadSelector:@selector(parseFeedData:) toTarget:self withObject:bloggerData]; // farkData will be retained by the thread until parseFarkData: has finished executing, so we no longer need // a reference to it in the main thread. self.bloggerData = nil; } If you read this from the top down you can see when the NSURLConnection is finished I detach a new thread and call parseFeedData. - (void)parseFeedData:(NSData *)data { // You must create a autorelease pool for all secondary threads. NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; self.currentParseBatch = [NSMutableArray array]; self.currentParsedCharacterData = [NSMutableString string]; self.feedList = [NSMutableArray array]; // // It's also possible to have NSXMLParser download the data, by passing it a URL, but this is not desirable // because it gives less control over the network, particularly in responding to connection errors. // NSXMLParser *parser = [[NSXMLParser alloc] initWithData:data]; [parser setDelegate:self]; [parser parse]; // depending on the total number of links parsed, the last batch might not have been a "full" batch, and thus // not been part of the regular batch transfer. So, we check the count of the array and, if necessary, send it to the main thread. if ([self.currentParseBatch count] > 0) { [self performSelectorOnMainThread:@selector(addLinksToList:) withObject:self.currentParseBatch waitUntilDone:NO]; } self.currentParseBatch = nil; self.currentParsedCharacterData = nil; [parser release]; [pool release]; } In the did end element delegate I check to see that 5 items have been parsed before calling the main thread to perform the update. - (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName { if ([elementName isEqualToString:kItemElementName]) { [self.currentParseBatch addObject:self.currentItem]; parsedItemsCounter++; if (parsedItemsCounter % kSizeOfItemBatch == 0) { [self performSelectorOnMainThread:@selector(addLinksToList:) withObject:self.currentParseBatch waitUntilDone:NO]; self.currentParseBatch = [NSMutableArray array]; } } // Stop accumulating parsed character data. We won't start again until specific elements begin. accumulatingParsedCharacterData = NO; } - (void)addLinksToList:(NSMutableArray *)links { [self.feedList addObjectsFromArray:links]; // The table needs to be reloaded to reflect the new content of the list. if (self.viewDelegate != nil && [self.viewDelegate respondsToSelector:@selector(parser:didParseBatch:)]) { [self.viewDelegate parser:self didParseBatch:links]; } } Finally, the UIViewController delegate: - (void)parser:(XMLFeedParser *)parser didParseBatch:(NSMutableArray *)parsedBatch { NSLog(@"parser:didParseBatch:"); [self.selectedBlogger.feedList addObjectsFromArray:parsedBatch]; [self.tableView reloadData]; } If I write to the log when my view controller delegate fires to reload the table and when cellForRowAtIndexPath fires as it's rebuilding the table then the log looks something like this: parser:didParseBatch: parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: parser:didParseBatch: parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: parser:didParseBatch: parser:didParseBatch: parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath Clearly, the tableView is not reloading when I tell it to every time. The log from the app that works correctly looks like this: parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath

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• Popping UIView crashes app

  - by Adun

  I'm basically pushing a UIView from a UITableViewController and all it contains is a UIWebView. However when I remove the UIView to return back to the UITableView the app crashes. - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { // Navigation logic may go here. Create and push another view controller. if (indexPath.row == websiteCell) { NSString *urlPath = [NSString stringWithFormat:@"http://%@", exhibitor.website]; WebViewController *webViewController = [[WebViewController alloc] initWithURLString:urlPath]; // Pass the selected object to the new view controller. [self.parentViewController presentModalViewController:webViewController animated:YES]; [webViewController release]; } } If I comment out the [webViewController release] the app doesn't crash, but I know that this would be a leak. Below is the code for the Web Browser: #import "WebViewController.h" @implementation WebViewController @synthesize webBrowserView; @synthesize urlValue; @synthesize toolBar; @synthesize spinner; @synthesize loadUrl; -(id)initWithURLString:(NSString *)urlString { if (self = [super init]) { urlValue = urlString; } return self; } #pragma mark WebView Controls - (void)goBack { [webBrowserView goBack]; } - (void)goForward { [webBrowserView goForward]; } - (void)reload { [webBrowserView reload]; } - (void)closeBrowser { [self.parentViewController dismissModalViewControllerAnimated:YES]; } #pragma end // Implement viewDidLoad to do additional setup after loading the view, typically from a nib. - (void)viewDidLoad { [super viewDidLoad]; CGRect contentRect = self.view.bounds; //NSLog(@"%f", contentRect.size.height); float webViewHeight = contentRect.size.height - 44.0f; // navBar = 44 float toolBarHeight = contentRect.size.height - webViewHeight; // navigation bar UINavigationBar *navBar = [[[UINavigationBar alloc] initWithFrame:CGRectMake(0, 20, contentRect.size.width, 44)] autorelease]; navBar.delegate = self; UIBarButtonItem *doneButton = [[[UIBarButtonItem alloc] initWithTitle:@"Done" style:UIBarButtonItemStyleDone target:nil action:@selector(closeBrowser)] autorelease]; UINavigationItem *item = [[[UINavigationItem alloc] initWithTitle:@"CEDIA10"] autorelease]; item.leftBarButtonItem = doneButton; [navBar pushNavigationItem:item animated:NO]; [self.view addSubview:navBar]; // web browser webBrowserView = [[UIWebView alloc] initWithFrame:CGRectMake(0, 64, contentRect.size.width, webViewHeight)]; webBrowserView.delegate = self; webBrowserView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight; webBrowserView.scalesPageToFit = YES; [self.view addSubview:webBrowserView]; // buttons UIBarButtonItem *backButton = [[[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"arrowleft.png"] style:UIBarButtonItemStylePlain target:self action:@selector(goBack)] autorelease]; UIBarButtonItem *fwdButton = [[[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"arrowright.png"] style:UIBarButtonItemStylePlain target:self action:@selector(goForward)] autorelease]; UIBarButtonItem *refreshButton = [[[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemRefresh target:self action:@selector(reload)] autorelease]; UIBarButtonItem *flexSpace = [[[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil] autorelease]; UIBarButtonItem *fixSpace = [[[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace target:nil action:nil] autorelease]; [fixSpace setWidth: 40.0f]; spinner = [[[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite] autorelease]; [spinner startAnimating]; UIBarButtonItem *loadingIcon = [[[UIBarButtonItem alloc] initWithCustomView:spinner] autorelease]; NSArray *toolBarButtons = [[NSArray alloc] initWithObjects: fixSpace, backButton, fixSpace, fwdButton, flexSpace, loadingIcon, flexSpace, refreshButton, nil]; // toolbar toolBar = [[UIToolbar alloc] initWithFrame:CGRectMake(0, webViewHeight, contentRect.size.width, toolBarHeight)]; toolBar.autoresizingMask = UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleWidth; toolBar.items = toolBarButtons; [self.view addSubview:toolBar]; // load the request NSURL *requestString = [NSURL URLWithString:urlValue]; [webBrowserView loadRequest:[NSURLRequest requestWithURL: requestString]]; [toolBarButtons release]; } - (void)viewWillDisappear { if ([webBrowserView isLoading]) { [webBrowserView stopLoading]; webBrowserView.delegate = nil; } } #pragma mark UIWebView - (void)webViewDidStartLoad:(UIWebView*)webView { [spinner startAnimating]; } - (void)webViewDidFinishLoad:(UIWebView*)webView { [spinner stopAnimating]; } - (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType { loadUrl = [[request URL] retain]; if ([[loadUrl scheme] isEqualToString: @"mailto"]) { UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"CEDIA10" message:@"Do you want to open Mail and exit AREC10?" delegate:self cancelButtonTitle:@"No" otherButtonTitles:@"Yes",nil]; [alert show]; [alert release]; return NO; } [loadUrl release]; return YES; } - (void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error { [spinner stopAnimating]; if (error.code == -1009) { // no internet connection UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"CEDIA10" message:@"You need an active Internet connection." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil]; [alert show]; [alert release]; } } #pragma mark UIAlertView - (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex { if (buttonIndex == 1) { [[UIApplication sharedApplication] openURL:loadUrl]; [loadUrl release]; } } - (void)didReceiveMemoryWarning { // Releases the view if it doesn't have a superview. [super didReceiveMemoryWarning]; // Release any cached data, images, etc that aren't in use. [webBrowserView release]; [urlValue release]; [toolBar release]; [spinner release]; [loadUrl release]; webBrowserView = nil; webBrowserView.delegate = nil; urlValue = nil; toolBar = nil; spinner = nil; loadUrl = nil; } - (void)viewDidUnload { // Release any retained subviews of the main view. // e.g. self.myOutlet = nil; } - (void)dealloc { [webBrowserView release]; [urlValue release]; [toolBar release]; [spinner release]; [loadUrl release]; webBrowserView.delegate = nil; urlValue = nil; toolBar = nil; spinner = nil; loadUrl = nil; [super dealloc]; } @end Below this is the crash log that I am getting: Date/Time: 2010-05-13 11:58:20.023 +1000 OS Version: iPhone OS 3.1.3 (7E18) Report Version: 104 Exception Type: EXC_CRASH (SIGABRT) Exception Codes: 0x00000000, 0x00000000 Crashed Thread: 0 Thread 0 Crashed: 0 libSystem.B.dylib 0x00090b2c __kill + 8 1 libSystem.B.dylib 0x00090b1a kill + 4 2 libSystem.B.dylib 0x00090b0e raise + 10 3 libSystem.B.dylib 0x000a7e34 abort + 36 4 libstdc++.6.dylib 0x00066390 __gnu_cxx::__verbose_terminate_handler() + 588 5 libobjc.A.dylib 0x00008898 _objc_terminate + 160 6 libstdc++.6.dylib 0x00063a84 __cxxabiv1::__terminate(void (*)()) + 76 7 libstdc++.6.dylib 0x00063afc std::terminate() + 16 8 libstdc++.6.dylib 0x00063c24 __cxa_throw + 100 9 libobjc.A.dylib 0x00006e54 objc_exception_throw + 104 10 CoreFoundation 0x00095bf6 -[NSObject doesNotRecognizeSelector:] + 106 11 CoreFoundation 0x0001ab12 ___forwarding___ + 474 12 CoreFoundation 0x00011838 _CF_forwarding_prep_0 + 40 13 QuartzCore 0x0000f448 CALayerCopyRenderLayer + 24 14 QuartzCore 0x0000f048 CA::Context::commit_layer(_CALayer*, unsigned int, unsigned int, void*) + 100 15 QuartzCore 0x0000ef34 CALayerCommitIfNeeded + 336 16 QuartzCore 0x0000eedc CALayerCommitIfNeeded + 248 17 QuartzCore 0x00011ee8 CA::Context::commit_root(void*, void*) + 52 18 QuartzCore 0x00011e80 x_hash_table_foreach + 64 19 QuartzCore 0x00011e2c CA::Transaction::foreach_root(void (*)(void*, void*), void*) + 40 20 QuartzCore 0x0000bb68 CA::Context::commit_transaction(CA::Transaction*) + 1068 21 QuartzCore 0x0000b46c CA::Transaction::commit() + 276 22 QuartzCore 0x000135d4 CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 84 23 CoreFoundation 0x0000f82a __CFRunLoopDoObservers + 466 24 CoreFoundation 0x00057340 CFRunLoopRunSpecific + 1812 25 CoreFoundation 0x00056c18 CFRunLoopRunInMode + 44 26 GraphicsServices 0x000041c0 GSEventRunModal + 188 27 UIKit 0x00003c28 -[UIApplication _run] + 552 28 UIKit 0x00002228 UIApplicationMain + 960 29 CEDIA10 0x00002e16 main (main.m:14) 30 CEDIA10 0x00002db8 start + 32 Any ideas on why the app is crashing?

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• SocketChannel in Java sends data, but it doesn't get to destination application

  - by Peterson

  Hi Everybody, I'm suffering a lot to create a simple ChatServer in Java, using the NIO libraries. Wonder if someone could help me. I am doing that by using SocketChannel and Selector to handle multiple clients in a single thread. The problem is: I am able to accept new connections and get it's data, but when I try to send data back, the SocketChannel simply doesn't work. In the method write(), it returns a integer that is the same size of the data i'm passing to it, but the client never receives that data. Strangely, when I close the server application, the client receives the data. It's like the socketchannel maintains a buffer, and it only get flushed when I close the application. Here are some more details, to give you more information to help. I'm handling the events in this piece of code: private void run() throws IOException { ServerSocketChannel ssc = ServerSocketChannel.open(); // Set it to non-blocking, so we can use select ssc.configureBlocking( false ); // Get the Socket connected to this channel, and bind it // to the listening port this.serverSocket = ssc.socket(); InetSocketAddress isa = new InetSocketAddress( this.port ); serverSocket.bind( isa ); // Create a new Selector for selecting this.masterSelector = Selector.open(); // Register the ServerSocketChannel, so we can // listen for incoming connections ssc.register( masterSelector, SelectionKey.OP_ACCEPT ); while (true) { // See if we've had any activity -- either // an incoming connection, or incoming data on an // existing connection int num = masterSelector.select(); // If we don't have any activity, loop around and wait // again if (num == 0) { continue; } // Get the keys corresponding to the activity // that has been detected, and process them // one by one Set keys = masterSelector.selectedKeys(); Iterator it = keys.iterator(); while (it.hasNext()) { // Get a key representing one of bits of I/O // activity SelectionKey key = (SelectionKey)it.next(); // What kind of activity is it? if ((key.readyOps() & SelectionKey.OP_ACCEPT) == SelectionKey.OP_ACCEPT) { // Aceita a conexão Socket s = serverSocket.accept(); System.out.println( "LOG: Conexao TCP aceita de " + s.getInetAddress() + ":" + s.getPort() ); // Make sure to make it non-blocking, so we can // use a selector on it. SocketChannel sc = s.getChannel(); sc.configureBlocking( false ); // Registra a conexao no seletor, apenas para leitura sc.register( masterSelector, SelectionKey.OP_READ ); } else if ( key.isReadable() ) { SocketChannel sc = null; // It's incoming data on a connection, so // process it sc = (SocketChannel)key.channel(); // Verifica se a conexão corresponde a um cliente já existente if((clientsMap.getClient(key)) != null){ boolean closedConnection = !processIncomingClientData(key); if(closedConnection){ int id = clientsMap.getClient(key); closeClient(id); } } else { boolean clientAccepted = processIncomingDataFromNewClient(key); if(!clientAccepted){ // Se o cliente não foi aceito, sua conexão é simplesmente fechada sc.socket().close(); sc.close(); key.cancel(); } } } } // We remove the selected keys, because we've dealt // with them. keys.clear(); } } This piece of code is simply handles new clients that wants to connect to the chat. So, a client makes a TCP connection to the server, and once it gets accepted, it sends data to the server following a simply text protocol, informing his id and asking to get registrated to the server. I handle this in the method processIncomingDataFromNewClient(key). I'm also keeping a map of clients and its connections in a data structure similar to a hashtable. I? doing that because I need to recover a client Id from a connection and a connection from a client Id. This is can be shown in: clientsMap.getClient(key). But the problem itself resides in the method processIncomingDataFromNewClient(key). There, I simply read the data that the client sent to me, validate it, and if it's ok, I send a message back to the client to tell that it is connected to the chat server. Here is a similar piece of code: private boolean processIncomingDataFromNewClient(SelectionKey key){ SocketChannel sc = (SocketChannel) key.channel(); String connectionOrigin = sc.socket().getInetAddress() + ":" + sc.socket().getPort(); int id = 0; //id of the client buf.clear(); int bytesRead = 0; try { bytesRead = sc.read(buf); if(bytesRead<=0){ System.out.println("Conexão fechada pelo: " + connectionOrigin); return false; } System.out.println("LOG: " + bytesRead + " bytes lidos de " + connectionOrigin); String msg = new String(buf.array(),0,bytesRead); // Do validations with the client sent me here // gets the client id }catch (Exception e) { e.printStackTrace(); System.out.println("LOG: Oops. Cliente não conhece o protocolo. Fechando a conexão: " + connectionOrigin); System.out.println("LOG: Primeiros 10 caracteres enviados pelo cliente: " + msg); return false; } } } catch (IOException e) { System.out.println("LOG: Erro ao ler dados da conexao: " + connectionOrigin); System.out.println("LOG: "+ e.getLocalizedMessage()); System.out.println("LOG: Fechando a conexão..."); return false; } // If it gets to here, the protocol is ok and we can add the client boolean inserted = clientsMap.addClient(key, id); if(!inserted){ System.out.println("LOG: Não foi possível adicionar o cliente. Ou ele já está conectado ou já têm clientes demais. Id: " + id); System.out.println("LOG: Fechando a conexão: " + connectionOrigin); return false; } System.out.println("LOG: Novo cliente conectado! Enviando mesnsagem de confirmação. Id: " + id + " Conexao: " + connectionOrigin); /* Here is the error */ sendMessage(id, "Servidor pet: connection accepted"); System.out.println("LOG: Novo cliente conectado! Id: " + id + " Conexao: " + connectionOrigin); return true; } And finally, the method sendMessage(SelectionKey key) looks like this: private void sendMessage(int destId, String msg) { Charset charset = Charset.forName("ISO-8859-1"); CharBuffer charBuffer = CharBuffer.wrap(msg, 0, msg.length()); ByteBuffer bf = charset.encode(charBuffer); //bf.flip(); int bytesSent = 0; SelectionKey key = clientsMap.getClient(destId); SocketChannel sc = (SocketChannel) key.channel(); try { / int total_bytes_sent = 0; while(total_bytes_sent < msg.length()){ bytesSent = sc.write(bf); total_bytes_sent += bytesSent; } System.out.println("LOG: Bytes enviados para o cliente " + destId + ": "+ total_bytes_sent + " Tamanho da mensagem: " + msg.length()); } catch (IOException e) { System.out.println("LOG: Erro ao mandar mensagem para: " + destId); System.out.println("LOG: " + e.getLocalizedMessage()); } } So, what is happening is that the server, when send a message, prints something like this: LOG: Bytes sent to the client: 28 Size of the message: 28 So, it tells that it sent the data, but the chat client keeps blocking, waiting in the recv() method. So, the data never gets to it. When I close the server application, though, all the data appears in the client. I wonder why. It is important to say that the client is in C and the server JAVA, and I'm running both in the same machine, an Ubuntu Guest in virtualbox under windows. I also run both under windows host and under linuxes hosts, and keep getting the same strange problem. I'm sorry for the great lenght of this question, but I already searched a lot of places for an answer, found a lot of tutorials and questions, including here at StackOverflow, but coundn't find a reasonable explanation. I am really not liking this Java NIO, and i saw a lot of people complaining about it too. I am thinking that if I had done that in C it would have been a lot easier :-D So, if someone could help me and even discuss this behavor, it would be great! :-) Thanks everybody in advance, Péterson

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• PERC H710 mini raid controller advanced settings (BIOS)

  - by gregg

  I upgraded from a PERC h310 to an H710 controller on my Dell R620 but didnt get any increase in performance. This is a ESXi host with a 5 disk RAID 5. I noticed when going to the RAID BIOS that the advanced settings section was not activated/checked off. In that section is the strip element size: 64kb (default) read policy: no read ahead and the write policy: write-through. Will checking that section do any harm to the existing raid array or will it simply enable those policies and hopefully boost performance? Or, lastly, is it already using those policies and the checkmark is simply to activate them for changes

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• Intel® Core™2 Duo Desktop Processor vs Intel® Core™ i3 Desktop Processor?

  - by metal gear solid

  Intel® Core™2 Duo Desktop Processor vs Intel® Core™ i3 Desktop Processor? Which CPU is better to buy ? Intel® Core™ i3-530 Processor (4M Cache, 2.93 GHz) (it supports DDR3 also) or Intel® Core™2 Duo Processor E7500 (3M Cache, 2.93 GHz, 1066 MHz FSB) (it supports DDR2 only ) Although I do not play games on my PC but I need good performance in Adobe Photoshop, Watching Full HD Movies. I need good performance in Multitasking. Along with any of these CPU I would purchase 2 GB x 2 stick of RAM. and I will use Windows 7. and I will use Microsoft VPC images also with MS Virtual PC.

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• Remove automatic Aero disabling in Windows 7

  - by Jani Hartikainen

  Sometimes when I'm playing games which are heavy on the GPU, Windows decides to helpfully disable aero, causing everything to freeze for a bit and in the worst case, combined with ATI's brilliant drivers, causes the game to crash. So, How do I stop Windows from automatically disabling Aero when playing games? It has absolutely no effect on the performance of the game itself when it does that. Also, I'd like to get rid of the "You should disable Aero to improve performance" helpful hint popup which sometimes shows up. But I suppose getting rid of the first will get rid of the second, assuming anyone knows how.

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• Why are my uWSGI processes dying immediately?

  - by orokusaki

  I'm using Supervisor and the uWSGI Emperor mode. When I set limit-as to 512 (MB), workers die instantly (respawn, die, respawn, die, every 3/4 of a second or so): [uwsgi] workers = 4 threads = 40 limit-as = 512 harakiri = 20 max-requests = 1600 ... non-performance/memory/processor-related settings ommitted But, if I change limit-as to: [uwsgi] workers = 4 threads = 40 limit-as = 1024 harakiri = 20 max-requests = 1600 ... non-performance/memory/processor-related settings ommitted and restart uwsgi, the problem is gone immediately. In order to put a sham in this, I've modified the setting back to 512, restarted again, and the problem is back immediately. Notes: My app is a simple Django app without much additional Python setup during start-up time.

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• CgiModule and FastCgiModule in IIS7

  - by Hari

  My web server is IIS7 running on Windows 2008 Web edition. There are nearly 40 modules when checked pre-installed "Modules". It also having "CgiModule and FastCgiModules". All the websites installed on this server purely runs with ASP.NET technology. Can I remove these two modules to improve performance? Same way, my application uses "Forms Authentication" only. In such case can I delete "Windows Authentication and WindowsAuthenticationModule"?. Also please suggest if any other modules can be deleted to improve performance.

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• Is there a Windows equivalent of Unix 'CPU steal time'?

  - by Steffen Opel

  In order to assess performance monitoring accuracy on virtualization platforms, the CPU steal time has become an increasingly relevant metric - see EC2 monitoring: the case of stolen CPU for an instructive summary in the context of Amazon EC2 and IBM's paper on CPU time accounting for a more in-depth technical explanation (including illustrations) of the concept: Steal time is the percentage of time a virtual CPU waits for a real CPU while the hypervisor is servicing another virtual processor. Accordingly, it is exposed in most related Unix/Linux monitoring tools nowadays - see e.g. columns %steal or st in sar or top: st -- Steal Time The amount of CPU 'stolen' from this virtual machine by the hypervisor for other tasks (such as running another virtual machine). I've been unable to figure out how to capture the same metric on Windows though, is this possible already? (Ideally for the Windows 2008 Server R2 AMIs on EC2 and via a respective Windows Performance Counters of course.)

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• Intel P6100 CPU and Mobile Intel® HM55 Express Chipset

  - by Christopher Painter

  I have an Asus K52F-BBR5 notebook that uses an Intel P6100 ( 2GHZ 15x multiplier) and HM55 Express Chipset. I'm looking to replace it's 3GB with 8GB. The Crucial database seems to indicate that a PC3-8500 CAS 7 and PC3-10666 CAS 9 will both work. I'm not up to date on the latest DDR3 nomencalature and I'm wondering which would provide better performance. The price difference is negligible. Drawing on past experiences from many many years ago I could make an argument for either based on sync/async bus speed arguments and CAS latency differences but the truth is I don't know enough about the HM55 chipset to know which would be the correct choice. Does anyone know the answer or point me to information that would help me make the choice? I'm pretty sure the performance difference will be somewhat negligible also but still I'd like to make the optimal choice.

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• Linux memory fragmentation

  - by Raghu

  Hi all, Is there a way to detect memory fragmentation on linux ? This is because on some long running servers I have noticed performance degradation and only after I restart process I see better performance. I noticed it more when using linux huge page support -- are huge pages in linux more prone to fragmentation ? I have looked at /proc/buddyinfo in particular. I want to know whether there are any better ways(not just CLI commands per se, any program or theoretical background would do) to look at it.

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• Oracle on NFS vmdk beats native NFS!?

  - by fletch00

  Hi, my colleagues are pursuing this with Netapp and Oracle - but I thought I'd post here on the off chance someone else has seen this We have a RedHat 5 VM (fully up2date) running Oracle 11i with data disks mounted via the VM's linux kernel NFS using Oracle's recommended mount options and the performance is very inconsistent (Querys that should take < 2 seconds sometimes take 60 seconds) Funny thing is we can run the same queries perfectly consistently < 2 seconds on a VMDK residing on SAME NetApp NFS datastore! Makes me wish Oracle and NetApp collaborated as closely as VMware and NetApp did on the Virtual Storage Console we used to perfectly set the NFS options and keep them in compliance... We have tried a few Linux NFS options others have posted and not seen improvement so far. We are now creating VMDK's for the VM to replace the Linux NFS mounted and workaround the issue as our developers need consistent performance ASAP.

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• why doesn't System Rating work properly?

  - by Ehsan Mamakani

  I have windows7 when I want to run system rating after about 60% progress it stops with this error: "could not measure processor performance"

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• How to use router QoS?

  - by Nathaniel

  N00b question. How exactly does one use router quality of service settings? I've read up on it a bit but I'm still not exactly sure how to use it. So, my real questions are these: Generally, how does QoS work? How would one use it, say, to guarantee smooth performance in latency sensitive application (cough online gaming cough)? Performance for that sort of stuff bombs out on our connection when somebody is uploading files. I apologize if this is kind of sprawling. Suggestions to clean it up / edits welcome.

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• ZFS/Btrfs/LVM2-like storage with advanced features on Linux?

  - by Easter Sunshine

  I have 3 identical internal 7200 RPM SATA hard disk drives on a Linux machine. I'm looking for a storage set-up that will give me all of this: Different data sets (filesystems or subtrees) can have different RAID levels so I can choose performance, space overhead, and risk trade-offs differently for different data sets while having a few number of physical disks (very important data can be 3xRAID1, important data can be 3xRAID5, unimportant reproducible data can be 3xRAID0). If each data set has an explicit size or size limit, then the ability to grow and shrink the size limit (offline if need be) Avoid out-of-kernel modules R/W or read-only COW snapshots. If it's a block-level snapshots, the filesystem should be synced and quiesced during a snapshot. Ability to add physical disks and then grow/redistribute RAID1, RAID5, and RAID0 volumes to take advantage of the new spindle and make sure no spindle is hotter than the rest (e.g., in NetApp, growing a RAID-DP raid group by a few disks will not balance the I/O across them without an explicit redistribution) Not required but nice-to-haves: Transparent compression, per-file or subtree. Even better if, like NetApps, analyzes the data first for compressibility and only compresses compressible data Deduplication that doesn't have huge performance penalties or require obscene amounts of memory (NetApp does scheduled deduplication on weekends, which is good) Resistance to silent data corruption like ZFS (this is not required because I have never seen ZFS report any data corruption on these specific disks) Storage tiering, either automatic (based on caching rules) or user-defined rules (yes, I have all-identical disks now but this will let me add a read/write SSD cache in the future). If it's user-defined rules, these rules should have the ability to promote to SSD on a file level and not a block level. Space-efficient packing of small files I tried ZFS on Linux but the limitations were: Upgrading is additional work because the package is in an external repository and is tied to specific kernel versions; it is not integrated with the package manager Write IOPS does not scale with number of devices in a raidz vdev. Cannot add disks to raidz vdevs Cannot have select data on RAID0 to reduce overhead and improve performance without additional physical disks or giving ZFS a single partition of the disks ext4 on LVM2 looks like an option except I can't tell whether I can shrink, extend, and redistribute onto new spindles RAID-type logical volumes (of course, I can experiment with LVM on a bunch of files). As far as I can tell, it doesn't have any of the nice-to-haves so I was wondering if there is something better out there. I did look at LVM dangers and caveats but then again, no system is perfect.

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• How to add nvidia drivers after previous failure with linux mint?

  - by LessThanMe

  Before today, I had perfectly good drivers from nvidia for my linux mint (15) box. I decided to update it because my performance in TF2 is less than stellar, and then things went south. I used synaptic to install nvidia-331 and then rebooted, but when I selected Mint in GRUB I waited...and waited...and waited. Nothing happened, but the display stayed on (a completely black video was being output). So I went into recovery mode from GRUB, went to root access, and apt-get remove --purge nvidia*'d my way out of that mess, and installed nvidia-common. Now my performance in graphic intensive stuff (read: games, blender) sucks, so I've been through the same thing a few times trying to re-install nvidia-current. I just want to get it back how it was. Thanks for any help! Nvidia GTX 560

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• High Load mysql on Debian server stops every day. Why?

  - by Oleg Abrazhaev

  I have Debian server with 32 gb memory. And there is apache2, memcached and nginx on this server. Memory load always on maximum. Only 500m free. Most memory leak do MySql. Apache only 70 clients configured, other services small memory usage. When mysql use all memory it stops. And nothing works, need mysql reboot. Mysql configured use maximum 24 gb memory. I have hight weight InnoDB bases. (400000 rows, 30 gb). And on server multithread daemon, that makes many inserts in this tables, thats why InnoDB. There is my mysql config. [mysqld] # # * Basic Settings # default-time-zone = "+04:00" user = mysql pid-file = /var/run/mysqld/mysqld.pid socket = /var/run/mysqld/mysqld.sock port = 3306 basedir = /usr datadir = /var/lib/mysql tmpdir = /tmp language = /usr/share/mysql/english skip-external-locking default-time-zone='Europe/Moscow' # # Instead of skip-networking the default is now to listen only on # localhost which is more compatible and is not less secure. # # * Fine Tuning # #low_priority_updates = 1 concurrent_insert = ALWAYS wait_timeout = 600 interactive_timeout = 600 #normal key_buffer_size = 2024M #key_buffer_size = 1512M #70% hot cache key_cache_division_limit= 70 #16-32 max_allowed_packet = 32M #1-16M thread_stack = 8M #40-50 thread_cache_size = 50 #orderby groupby sort sort_buffer_size = 64M #same myisam_sort_buffer_size = 400M #temp table creates when group_by tmp_table_size = 3000M #tables in memory max_heap_table_size = 3000M #on disk open_files_limit = 10000 table_cache = 10000 join_buffer_size = 5M # This replaces the startup script and checks MyISAM tables if needed # the first time they are touched myisam-recover = BACKUP #myisam_use_mmap = 1 max_connections = 200 thread_concurrency = 8 # # * Query Cache Configuration # #more ignored query_cache_limit = 50M query_cache_size = 210M #on query cache query_cache_type = 1 # # * Logging and Replication # # Both location gets rotated by the cronjob. # Be aware that this log type is a performance killer. #log = /var/log/mysql/mysql.log # # Error logging goes to syslog. This is a Debian improvement :) # # Here you can see queries with especially long duration log_slow_queries = /var/log/mysql/mysql-slow.log long_query_time = 1 log-queries-not-using-indexes # # The following can be used as easy to replay backup logs or for replication. # note: if you are setting up a replication slave, see README.Debian about # other settings you may need to change. #server-id = 1 #log_bin = /var/log/mysql/mysql-bin.log server-id = 1 log-bin = /var/lib/mysql/mysql-bin #replicate-do-db = gate log-bin-index = /var/lib/mysql/mysql-bin.index log-error = /var/lib/mysql/mysql-bin.err relay-log = /var/lib/mysql/relay-bin relay-log-info-file = /var/lib/mysql/relay-bin.info relay-log-index = /var/lib/mysql/relay-bin.index binlog_do_db = 24avia expire_logs_days = 10 max_binlog_size = 100M read_buffer_size = 4024288 innodb_buffer_pool_size = 5000M innodb_flush_log_at_trx_commit = 2 innodb_thread_concurrency = 8 table_definition_cache = 2000 group_concat_max_len = 16M #binlog_do_db = gate #binlog_ignore_db = include_database_name # # * BerkeleyDB # # Using BerkeleyDB is now discouraged as its support will cease in 5.1.12. #skip-bdb # # * InnoDB # # InnoDB is enabled by default with a 10MB datafile in /var/lib/mysql/. # Read the manual for more InnoDB related options. There are many! # You might want to disable InnoDB to shrink the mysqld process by circa 100MB. #skip-innodb # # * Security Features # # Read the manual, too, if you want chroot! # chroot = /var/lib/mysql/ # # For generating SSL certificates I recommend the OpenSSL GUI "tinyca". # # ssl-ca=/etc/mysql/cacert.pem # ssl-cert=/etc/mysql/server-cert.pem # ssl-key=/etc/mysql/server-key.pem [mysqldump] quick quote-names max_allowed_packet = 500M [mysql] #no-auto-rehash # faster start of mysql but no tab completition [isamchk] key_buffer = 32M key_buffer_size = 512M # # * NDB Cluster # # See /usr/share/doc/mysql-server-*/README.Debian for more information. # # The following configuration is read by the NDB Data Nodes (ndbd processes) # not from the NDB Management Nodes (ndb_mgmd processes). # # [MYSQL_CLUSTER] # ndb-connectstring=127.0.0.1 # # * IMPORTANT: Additional settings that can override those from this file! # The files must end with '.cnf', otherwise they'll be ignored. # !includedir /etc/mysql/conf.d/ Please, help me make it stable. Memory used /etc/mysql # free total used free shared buffers cached Mem: 32930800 32766424 164376 0 139208 23829196 -/+ buffers/cache: 8798020 24132780 Swap: 33553328 44660 33508668 Maybe my problem not in memory, but MySQL stops every day. As you can see, cache memory free 24 gb. Thank to Michael Hampton? for correction. Load overage on server 3.5. Maybe hdd or another problem? Maybe my config not optimal for 30gb InnoDB ? I'm already try mysqltuner and tunung-primer.sh , but they marked all green. Mysqltuner output mysqltuner >> MySQLTuner 1.0.1 - Major Hayden <[email protected]> >> Bug reports, feature requests, and downloads at http://mysqltuner.com/ >> Run with '--help' for additional options and output filtering -------- General Statistics -------------------------------------------------- [--] Skipped version check for MySQLTuner script [OK] Currently running supported MySQL version 5.5.24-9-log [OK] Operating on 64-bit architecture -------- Storage Engine Statistics ------------------------------------------- [--] Status: -Archive -BDB -Federated +InnoDB -ISAM -NDBCluster [--] Data in MyISAM tables: 112G (Tables: 1528) [--] Data in InnoDB tables: 39G (Tables: 340) [--] Data in PERFORMANCE_SCHEMA tables: 0B (Tables: 17) [!!] Total fragmented tables: 344 -------- Performance Metrics ------------------------------------------------- [--] Up for: 8h 18m 33s (14M q [478.333 qps], 259K conn, TX: 9B, RX: 5B) [--] Reads / Writes: 84% / 16% [--] Total buffers: 10.5G global + 81.1M per thread (200 max threads) [OK] Maximum possible memory usage: 26.3G (83% of installed RAM) [OK] Slow queries: 1% (259K/14M) [!!] Highest connection usage: 100% (201/200) [OK] Key buffer size / total MyISAM indexes: 1.5G/5.6G [OK] Key buffer hit rate: 100.0% (6B cached / 1M reads) [OK] Query cache efficiency: 74.3% (8M cached / 11M selects) [OK] Query cache prunes per day: 0 [OK] Sorts requiring temporary tables: 0% (0 temp sorts / 247K sorts) [!!] Joins performed without indexes: 106025 [!!] Temporary tables created on disk: 49% (351K on disk / 715K total) [OK] Thread cache hit rate: 99% (249 created / 259K connections) [!!] Table cache hit rate: 15% (2K open / 13K opened) [OK] Open file limit used: 15% (3K/20K) [OK] Table locks acquired immediately: 99% (4M immediate / 4M locks) [!!] InnoDB data size / buffer pool: 39.4G/5.9G -------- Recommendations ----------------------------------------------------- General recommendations: Run OPTIMIZE TABLE to defragment tables for better performance MySQL started within last 24 hours - recommendations may be inaccurate Reduce or eliminate persistent connections to reduce connection usage Adjust your join queries to always utilize indexes Temporary table size is already large - reduce result set size Reduce your SELECT DISTINCT queries without LIMIT clauses Increase table_cache gradually to avoid file descriptor limits Variables to adjust: max_connections (> 200) wait_timeout (< 600) interactive_timeout (< 600) join_buffer_size (> 5.0M, or always use indexes with joins) table_cache (> 10000) innodb_buffer_pool_size (>= 39G) Mysql primer output -- MYSQL PERFORMANCE TUNING PRIMER -- - By: Matthew Montgomery - MySQL Version 5.5.24-9-log x86_64 Uptime = 0 days 8 hrs 20 min 50 sec Avg. qps = 478 Total Questions = 14369568 Threads Connected = 16 Warning: Server has not been running for at least 48hrs. It may not be safe to use these recommendations To find out more information on how each of these runtime variables effects performance visit: http://dev.mysql.com/doc/refman/5.5/en/server-system-variables.html Visit http://www.mysql.com/products/enterprise/advisors.html for info about MySQL's Enterprise Monitoring and Advisory Service SLOW QUERIES The slow query log is enabled. Current long_query_time = 1.000000 sec. You have 260626 out of 14369701 that take longer than 1.000000 sec. to complete Your long_query_time seems to be fine BINARY UPDATE LOG The binary update log is enabled Binlog sync is not enabled, you could loose binlog records during a server crash WORKER THREADS Current thread_cache_size = 50 Current threads_cached = 45 Current threads_per_sec = 0 Historic threads_per_sec = 0 Your thread_cache_size is fine MAX CONNECTIONS Current max_connections = 200 Current threads_connected = 11 Historic max_used_connections = 201 The number of used connections is 100% of the configured maximum. You should raise max_connections INNODB STATUS Current InnoDB index space = 214 M Current InnoDB data space = 39.40 G Current InnoDB buffer pool free = 0 % Current innodb_buffer_pool_size = 5.85 G Depending on how much space your innodb indexes take up it may be safe to increase this value to up to 2 / 3 of total system memory MEMORY USAGE Max Memory Ever Allocated : 23.46 G Configured Max Per-thread Buffers : 15.84 G Configured Max Global Buffers : 7.54 G Configured Max Memory Limit : 23.39 G Physical Memory : 31.40 G Max memory limit seem to be within acceptable norms KEY BUFFER Current MyISAM index space = 5.61 G Current key_buffer_size = 1.47 G Key cache miss rate is 1 : 5578 Key buffer free ratio = 77 % Your key_buffer_size seems to be fine QUERY CACHE Query cache is enabled Current query_cache_size = 200 M Current query_cache_used = 101 M Current query_cache_limit = 50 M Current Query cache Memory fill ratio = 50.59 % Current query_cache_min_res_unit = 4 K MySQL won't cache query results that are larger than query_cache_limit in size SORT OPERATIONS Current sort_buffer_size = 64 M Current read_rnd_buffer_size = 256 K Sort buffer seems to be fine JOINS Current join_buffer_size = 5.00 M You have had 106606 queries where a join could not use an index properly You have had 8 joins without keys that check for key usage after each row join_buffer_size >= 4 M This is not advised You should enable "log-queries-not-using-indexes" Then look for non indexed joins in the slow query log. OPEN FILES LIMIT Current open_files_limit = 20210 files The open_files_limit should typically be set to at least 2x-3x that of table_cache if you have heavy MyISAM usage. Your open_files_limit value seems to be fine TABLE CACHE Current table_open_cache = 10000 tables Current table_definition_cache = 2000 tables You have a total of 1910 tables You have 2151 open tables. The table_cache value seems to be fine TEMP TABLES Current max_heap_table_size = 2.92 G Current tmp_table_size = 2.92 G Of 366426 temp tables, 49% were created on disk Perhaps you should increase your tmp_table_size and/or max_heap_table_size to reduce the number of disk-based temporary tables Note! BLOB and TEXT columns are not allow in memory tables. If you are using these columns raising these values might not impact your ratio of on disk temp tables. TABLE SCANS Current read_buffer_size = 3 M Current table scan ratio = 2846 : 1 read_buffer_size seems to be fine TABLE LOCKING Current Lock Wait ratio = 1 : 185 You may benefit from selective use of InnoDB. If you have long running SELECT's against MyISAM tables and perform frequent updates consider setting 'low_priority_updates=1'

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• Changing an MSSQL clustered index field from containing "random" GUIDs to sequential GUIDs - how wil

  - by Eyvind

  We have an MSSQL database in which all the primary keys are GUIDs (uniqueidentifiers). The GUIDs are produced on the client (in C#), and we are considering changing the client to generate sequential (comb) GUIDs instead of just using Guid.NewGuid(), to improve db performance. If we do this, how will this affect installations that already have data with "random" GUIDs as clustered PKs? Can anything be done (short of changing all the PK values) to rebuild the indexes to avoid further fragmentation and bad insert performance? Please give explicit and detailed answers if you can; I am a C# developer at heart and not all too familiar with all the intricacies of SQL Server. Thanks!

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• Reduce the I/O priority of Windows Backup (Windows Server 2008 R2)

  - by HelloSam

  I have a PostgreSQL running on Windows Server 2008 R2 x64 box. And I have scheduled a backup everyday from the RAID 1 DB disk to a dedicated standalone disk. They are SAS 15k on Dell PERC 6i. I am using the built-in Windows Server Backup for purpose. The problem is, whenever the backup process is kicked in, the database performance is hogged. I would say almost a 10x of performance reduction. From the resource monitor, the disk queue is in the double digit range when backing up, and less than 1 during the day. The disk activity is like ~30-50MB/s during backup, so I guess the hardware is acting normally, though wbengine.exe takes up most of the portions. I think reduce the IO priority of the backup process would be an answer, but I couldn't find a way to. Tuning process CPU priority does not seems to help.

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• NETAPP Fragmentation

  - by mdpc

  We all know that once a disk (or storage system for that matter) gets introduced into use, the performance degrades due to fragmentation of files. This seems to be why disk defragmentors are in fairly wide use on Windows boxes. And they do increase the performance substancially. As an aside, I haven't heard of many defragmentors in the Unix/Linux area. Despite the claimed WAFL protections for the NetApp, file fragmentation still will occur, especially with all the sparsely crated VMs. My question is does anybody do any sort of defragmention of such a storage system? Do you notice any measurable degration/improvement of either not doing/doing anything to address this situation? Does anybody do anything about it? If so what? Thanks

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• Cheapest server per gigabit throughput [closed]

  - by nethgirb

  I'm looking for a set of servers for performance testing a network, and secondarily testing some applications on the servers. Their most important task is simply to pump out data: from an application like memcached or just dumped from a large file in memory into a TCP flow (i.e., disk performance doesn't matter). This should happen over one or more 1 gigabit Ethernet ports, and the machines should run Linux (ideally), or perhaps Mac OS X or some other *nix. Other than that, there are few constraints (e.g., even something ARM-based could be fine). So here's the question: What's the cheapest server per gigabit? Price and power are both considerations.

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• Should my servers boot from VHD?

  - by tony roth

  I've been testing native vhd boot on several servers. It seems to be pretty transparent in terms of deployment and with my seat of the pants testing I have not noticed any difference in performance. The main reason that I want to boot vhd is due to their transportablility between different hardware and to hyper-v servers. the following roles will be installed. dfsr dhcp iis application server dc <- haven't tested this yet but see no reason why it won't work. With the above low impact (in terms of performance) roles do you thing booting from VHD is appropriate. thx

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• What is the best file system and allocation size for a USB flash drive?

  - by e-t172

  I'm considering using my 4 GB Kingston DataTraveler USB stick to store my Firefox and Thunderbird profiles for my laptop and desktop PCs. I want to maximize performance when using Firefox. The question is: what is the best file system and allocation size for the fastest Firefox profile operation on a USB flash drive? I'm using Windows 7 on both machines and I don't care about compatibility or the drive's lifetime. I just want to maximize performance. I could even use ext2 with the Ext2 IFS driver if that means it'll be faster. I'm assuming (perhaps I'm wrong) that putting a Firefox profile on a USB stick would be a "lots of small files" usage. In that case, it seems that NTFS would perform best, but I'm not sure. Besides I found nothing regarding the best allocation size to use. Considering that the default allocation size is designed for hard drives (which have different characteristics), I'm assuming that the default allocation size is not the best.

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• Video memory buswidth vs video memory Bandwidth

  - by Mixxiphoid

  My current video card (9600GT) is dying and I'm searching for a new video card. Between acquiring my current one and now, I got a lot more knowledge about hardware and I want to use that to pick my new card. So I decided to not just buy some popular card blindly, but to search for a card able to handle my hardware requirements. I searched the specs at the NVidia site for the GT640 and was confused by the memory section and some questions raised. My current card's memory bus width is 256bit and has 1GB of memory. I checked Google about the importance of bus width. And all the links basically said the same 'The higher the number the more potential simultaneously traffic can be transferred'. This was already clear to me, yet there are currently a lot of new cards which are considered better than my current one with a lower bus width. To go in more detail about my question I copied the memory info from the NVidia site: GT 640 GT640 GDDR5 Memory Specs: Memory Clock 1.8 Gbps 5.0 Gbps Standard Memory Config 2048 MB 1024 MB Memory Interface DDR3 GDDR5 Memory Interface Width 128-bit 64-bit Memory Bandwidth (GB/sec) 28.5 40.0 What puzzled me is that the Memory Bandwidth seems to me the most important part, yet the lower bus width has the higher 'performance'. Is this due to the fact the memory interface is GDDR5 and is therefore able to have a higher memory clock speed (5Gbps)? If I am to buy a new video card, should I check the bus width? Memory clock? Bandwith? Amount of memory? My current card ahs 1GB memory, so I was searching for a 2GB memory card, but now I'm not so sure any more whether that is really 'better'. My main question: To me it seems that memory performance is made up by the combination of bus width and frequency. Is this true? If yes, why are there so many sites telling me I need to get a card with a high bus width? If no, then what IS important when it goes about memory performance on a video card. NOTE: The memory bandwidth is (almost) never displayed on vendor sites. How can I determine which card is better without knowing the bandwith?

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