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  • SQL Server Storage Internals 101

    This article is an extract from the book Tribal SQL. In this article, Mark S. Rasmussen offers a concise introduction to the physical storage internals behind SQL Server databases. He doesn't dive into every detail, but provides a simple, clear picture of how SQL Server stores data. Deployment Manager 2 is now free!The new version includes tons of new features and we've launched a completely free Starter Edition! Get Deployment Manager here

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  • REMINDER : SPARC T4 Servers and ZFS Storage Appliance Demo Equipment Purchase Opportunity

    - by Cinzia Mascanzoni
    Please mark your calendars for the SPARC T4 Servers and ZFS Storage Appliance Demo Program webcast on November 22nd at 12 noon GMT/ 1pm CET and learn how you can take the maximum advantage from this unique opportunity. The objective of this call is to share value, details, guidelines and rules of this demo program with you. Go on the EMEA VAD Resource Center to find more info and the details to access the webcast.

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  • Is Microsoft Azure Powering Apple`s iCloud?

    When Apple unveiled its iCloud service at its Worldwide Developer Conference in San Francisco last week some observers called the huge project game-changing. Few noted the challenges inherent in managing an online storage center of this magnitude. Now it looks like Apple has turned to Microsoft and Amazon for help.... Are You Ready for IPv6? Test Your IPv6 Readiness: Take the Challenge Now and Enter to Win an iPad!

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  • Storage Technology for the Home User

    <b>Linux Magazine:</b> "Sometimes you just have to get excited about what you can buy, hold in your hand, and use in your home machines. Let's look at some cool storage technology that the average desktop user can tackle."

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  • ??????Oracle Automatic Storage Management???·????????

    - by Yusuke.Yamamoto
    ????? ??:2010/03/01 ??:???? Oracle Database ?????? Automatic Storage Management(ASM) ? Oracle Database 10g ?????????Oracle ASM ? Oracle Database ?????????????·????????????·????????????????????????????????????????Oracle ASM ????????????????·?????????????????????????? ??????·???????????????·??????????????????????ASRU ???????ASRU ???????????? ????????? ????????????????? http://www.oracle.com/technetwork/jp/database/1005200-oracle-asm-and-tr-321865-ja.pdf

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  • How to organise storage for media content such as video and music?

    - by thor
    Currently, we have a single server hosting all content: music, video and software. This content is downloaded by users through HTTP. Now free space is coming to an end and we are exploring different ways of extending our storage capacity. We want to do it cheap, simple and reliable (protected from disk/ server faults). Currenly, we see two ways: Add a couple of cheap servers with 4 disks (RAID1 ?), run some distributed file-system on top, like GlusterFS. Pros: hopefully, we will see all our disks as single flat file system, just dump content into it and be done. Cons: could be tricky in configuration and handling of faults. Add a couple of cheap servers, all running HTTP servers. Each piece of content (be it a music file or video) is placed on randomly selected two servers. Pros: don't have to deal with RAID, as content is duplicated; single server failure does not bring down any part of content; doubled distribution capacity (as any signle file could be downloaded from any of two servers hosting it). Cons: requires some scripting on part of distribution of content, adding/ removing servers. Do we miss any other ways? Which of the aforementioned options seems to be the best?

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  • setup lowcost image storage server with 24x SSD array to get high IOPS?

    - by Nenad
    I want to build let's name it a lowcost Ra*san which would host for our social site the images (many millions) we have 5 sizes of every photo with 3 KB, 7 KB, 15 KB, 25 KB and 80 KB per Image. My idea is to build a Server with 24x consumer 240 GB SSD's in Raid 6 which will give me some 5 TB Disk space for the photo storage. To have HA I can add a 2nd one and use drdb. I'm looking to get above 150'000 IOPS (4K Random reads). As we mostly have read access only and rarely delete photos i think to go with consumer MLC SSD. I read many endurance reviews and don't see there a problem as long we don't rewrite the cells. What you think about my idea? - I'm not sure between Raid 6 or Raid 10 (more IOPS, cost SSD). - Is ext4 OK for the filesystem - Would you use 1 or 2 Raid controller, with Extender Backplane If anyone has realized something similar i would be happy to get Real World numbers. UPDATE I have buy 12 (plus some spare) OCZ Talos 480GB SAS SSD Drive's they will be placed in a 12-bay DAS and attached to a PERC H800 (1GB NV Cache, manufactured by LSI with fastpath) Controller, I plan to setup Raid 50 with ext4. If someone is wondering about some benchmarks let me know what you would like to see.

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  • How can I remove all drivers and other files related to a USB Mass Storage device?

    - by Bob
    I have a flash drive here that does not work on one OS on computer - let's call it the desktop Windows 7. It works fine on another computer - laptop Windows 7. It also works fine on Windows 8 on the same desktop computer. Other flash drives work fine under desktop Windows 7. So not a hardware issue, not a generic USB Mass Storage driver issue. It's something specific to this drive. On desktop Windows 7, I can connect the drive but no volume comes up under Windows Explorer. Ditto for Disk Management. With diskpart, loading hangs until I unplug the drive, if I replug it and try list disk it hangs again. If I unplug the drive at this point, list disk prints out all attached drives - including the just removed flash drive. The drive consistently appears under Device Manager, but uninstalling the drivers, restarting and reinstalling the drivers (by inserting the drive) only works for the first insertion. After that it fails again. I get the feeling that the driver files are not actually removed, and are corrupted, meaning every reinstall it's the same corrupted drivers being installed. Is there any way to remove these drivers completely? Or perhaps some other setting Windows 7 retains? Formatting the drive through another computer/OS does not help. I've also tried a complete wipe and rebuild of the MBR and single partition. The allocation unit size makes no difference; neither does a NTFS format. This is a relatively small matter, and I would not like to reinstall the entire OS!

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  • Noob with git repository on Windows Storage Server 2008?

    - by HibbyHoo
    I have a Western Digital Sentinel at home running Windows Storage Server 2008 R2 Essentials. I have several git repositories on it for my own personal projects, and have no problem pushing and pulling over my local network. I want to be able to access those repos remotely from anywhere. I am able to log in and remotely access folders and files on it, but I cannot clone repos using the same address. It hangs for a REALLY long time before finally failing with an error: git.exe clone --progress -v "https://myIpAddressHere/Remote/fs/files.aspx?path=%5C%5Cmydevicename%5Cmyreposfolder%5Cmyrepo.git" "D:\repo" Cloning into 'D:\repo'... error: Failed connect to myIpAddress:443; No error while accessing https://myIpAddress/Remote/fs/files.aspx?path=%5C%5Cmydevicename%5Cmyreposfolder%5Cmyrepo.git/info/refs fatal: HTTP request failed git did not exit cleanly (exit code 128) I'm not too privy to networking or web development, and I have only a rudimentary understanding of how to use git (with TortoiseGit). I'm having a hard time finding search results for this specific problem and a hard time interpreting generic tutorials for the general scope of this problem. TortoiseGit version: 1.7.13.0. git version: 1.7.10.mysysgit.1.

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  • SQL Azure: Notes on Building a Shard Technology

    - by Herve Roggero
    In Chapter 10 of the book on SQL Azure (http://www.apress.com/book/view/9781430229612) I am co-authoring, I am digging deeper in what it takes to write a Shard. It's actually a pretty cool exercise, and I wanted to share some thoughts on how I am designing the technology. A Shard is a technology that spreads the load of database requests over multiple databases, as transparently as possible. The type of shard I am building is called a Vertical Partition Shard  (VPS). A VPS is a mechanism by which the data is stored in one or more databases behind the scenes, but your code has no idea at design time which data is in which database. It's like having a mini cloud for records instead of services. Imagine you have three SQL Azure databases that have the same schema (DB1, DB2 and DB3), you would like to issue a SELECT * FROM Users on all three databases, concatenate the results into a single resultset, and order by last name. Imagine you want to ensure your code doesn't need to change if you add a new database to the shard (DB4). Now imagine that you want to make sure all three databases are queried at the same time, in a multi-threaded manner so your code doesn't have to wait for three database calls sequentially. Then, imagine you would like to obtain a breadcrumb (in the form of a new, virtual column) that gives you a hint as to which database a record came from, so that you could update it if needed. Now imagine all that is done through the standard SqlClient library... and you have the Shard I am currently building. Here are some lessons learned and techniques I am using with this shard: Parellel Processing: Querying databases in parallel is not too hard using the Task Parallel Library; all you need is to lock your resources when needed Deleting/Updating Data: That's not too bad either as long as you have a breadcrumb. However it becomes more difficult if you need to update a single record and you don't know in which database it is. Inserting Data: I am using a round-robin approach in which each new insert request is directed to the next database in the shard. Not sure how to deal with Bulk Loads just yet... Shard Databases:  I use a static collection of SqlConnection objects which needs to be loaded once; from there on all the Shard commands use this collection Extension Methods: In order to make it look like the Shard commands are part of the SqlClient class I use extension methods. For example I added ExecuteShardQuery and ExecuteShardNonQuery methods to SqlClient. Exceptions: Capturing exceptions in a multi-threaded code is interesting... but I kept it simple for now. I am using the ConcurrentQueue to store my exceptions. Database GUID: Every database in the shard is given a GUID, which is calculated based on the connection string's values. DataTable. The Shard methods return a DataTable object which can be bound to objects.  I will be sharing the code soon as an open-source project in CodePlex. Please stay tuned on twitter to know when it will be available (@hroggero). Or check www.bluesyntax.net for updates on the shard. Thanks!

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  • New Project Starting. Got Gas?

    - by merrillaldrich
    “Storage is just like gasoline,” said a fellow DBA at the office the other day. This DBA, Mike is his name, is one of the smartest people I know, so I pressed him, in my subtle and erudite way, to elaborate. “Um, whut?” I said. “Yeah. Now that everything is shared – VMs or consolidated SQL Servers and shared storage – if you want to do a big project, like, say, drive to Vegas, you better fill the car with gas. Drive back and forth to work every day? Gas. Same for storage.” This was a light-bulb-above-my-head...(read more)

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  • Windows Azure Service Bus Scatter-Gather Implementation

    - by Alan Smith
    One of the more challenging enterprise integration patterns that developers may wish to implement is the Scatter-Gather pattern. In this article I will show the basic implementation of a scatter-gather pattern using the topic-subscription model of the windows azure service bus. I’ll be using the implementation in demos, and also as a lab in my training courses, and the pattern will also be included in the next release of my free e-book the “Windows Azure Service Bus Developer Guide”. The Scatter-Gather pattern answers the following scenario. How do you maintain the overall message flow when a message needs to be sent to multiple recipients, each of which may send a reply? Use a Scatter-Gather that broadcasts a message to multiple recipients and re-aggregates the responses back into a single message. The Enterprise Integration Patterns website provides a description of the Scatter-Gather pattern here.   The scatter-gather pattern uses a composite of the publish-subscribe channel pattern and the aggregator pattern. The publish-subscribe channel is used to broadcast messages to a number of receivers, and the aggregator is used to gather the response messages and aggregate them together to form a single message. Scatter-Gather Scenario The scenario for this scatter-gather implementation is an application that allows users to answer questions in a poll based voting scenario. A poll manager application will be used to broadcast questions to users, the users will use a voting application that will receive and display the questions and send the votes back to the poll manager. The poll manager application will receive the users’ votes and aggregate them together to display the results. The scenario should be able to scale to support a large number of users.   Scatter-Gather Implementation The diagram below shows the overall architecture for the scatter-gather implementation.       Messaging Entities Looking at the scatter-gather pattern diagram it can be seen that the topic-subscription architecture is well suited for broadcasting a message to a number of subscribers. The poll manager application can send the question messages to a topic, and each voting application can receive the question message on its own subscription. The static limit of 2,000 subscriptions per topic in the current release means that 2,000 voting applications can receive question messages and take part in voting. The vote messages can then be sent to the poll manager application using a queue. The voting applications will send their vote messages to the queue, and the poll manager will receive and process the vote messages. The questions topic and answer queue are created using the Windows Azure Developer Portal. Each instance of the voting application will create its own subscription in the questions topic when it starts, allowing the question messages to be broadcast to all subscribing voting applications. Data Contracts Two simple data contracts will be used to serialize the questions and votes as brokered messages. The code for these is shown below.   [DataContract] public class Question {     [DataMember]     public string QuestionText { get; set; } }     To keep the implementation of the voting functionality simple and focus on the pattern implementation, the users can only vote yes or no to the questions.   [DataContract] public class Vote {     [DataMember]     public string QuestionText { get; set; }       [DataMember]     public bool IsYes { get; set; } }     Poll Manager Application The poll manager application has been implemented as a simple WPF application; the user interface is shown below. A question can be entered in the text box, and sent to the topic by clicking the Add button. The topic and subscriptions used for broadcasting the messages are shown in a TreeView control. The questions that have been broadcast and the resulting votes are shown in a ListView control. When the application is started any existing subscriptions are cleared form the topic, clients are then created for the questions topic and votes queue, along with background workers for receiving and processing the vote messages, and updating the display of subscriptions.   public MainWindow() {     InitializeComponent();       // Create a new results list and data bind it.     Results = new ObservableCollection<Result>();     lsvResults.ItemsSource = Results;       // Create a token provider with the relevant credentials.     TokenProvider credentials =         TokenProvider.CreateSharedSecretTokenProvider         (AccountDetails.Name, AccountDetails.Key);       // Create a URI for the serivce bus.     Uri serviceBusUri = ServiceBusEnvironment.CreateServiceUri         ("sb", AccountDetails.Namespace, string.Empty);       // Clear out any old subscriptions.     NamespaceManager = new NamespaceManager(serviceBusUri, credentials);     IEnumerable<SubscriptionDescription> subs =         NamespaceManager.GetSubscriptions(AccountDetails.ScatterGatherTopic);     foreach (SubscriptionDescription sub in subs)     {         NamespaceManager.DeleteSubscription(sub.TopicPath, sub.Name);     }       // Create the MessagingFactory     MessagingFactory factory = MessagingFactory.Create(serviceBusUri, credentials);       // Create the topic and queue clients.     ScatterGatherTopicClient =         factory.CreateTopicClient(AccountDetails.ScatterGatherTopic);     ScatterGatherQueueClient =         factory.CreateQueueClient(AccountDetails.ScatterGatherQueue);       // Start the background worker threads.     VotesBackgroundWorker = new BackgroundWorker();     VotesBackgroundWorker.DoWork += new DoWorkEventHandler(ReceiveMessages);     VotesBackgroundWorker.RunWorkerAsync();       SubscriptionsBackgroundWorker = new BackgroundWorker();     SubscriptionsBackgroundWorker.DoWork += new DoWorkEventHandler(UpdateSubscriptions);     SubscriptionsBackgroundWorker.RunWorkerAsync(); }     When the poll manager user nters a question in the text box and clicks the Add button a question message is created and sent to the topic. This message will be broadcast to all the subscribing voting applications. An instance of the Result class is also created to keep track of the votes cast, this is then added to an observable collection named Results, which is data-bound to the ListView control.   private void btnAddQuestion_Click(object sender, RoutedEventArgs e) {     // Create a new result for recording votes.     Result result = new Result()     {         Question = txtQuestion.Text     };     Results.Add(result);       // Send the question to the topic     Question question = new Question()     {         QuestionText = result.Question     };     BrokeredMessage msg = new BrokeredMessage(question);     ScatterGatherTopicClient.Send(msg);       txtQuestion.Text = ""; }     The Results class is implemented as follows.   public class Result : INotifyPropertyChanged {     public string Question { get; set; }       private int m_YesVotes;     private int m_NoVotes;       public event PropertyChangedEventHandler PropertyChanged;       public int YesVotes     {         get { return m_YesVotes; }         set         {             m_YesVotes = value;             NotifyPropertyChanged("YesVotes");         }     }       public int NoVotes     {         get { return m_NoVotes; }         set         {             m_NoVotes = value;             NotifyPropertyChanged("NoVotes");         }     }       private void NotifyPropertyChanged(string prop)     {         if(PropertyChanged != null)         {             PropertyChanged(this, new PropertyChangedEventArgs(prop));         }     } }     The INotifyPropertyChanged interface is implemented so that changes to the number of yes and no votes will be updated in the ListView control. Receiving the vote messages from the voting applications is done asynchronously, using a background worker thread.   // This runs on a background worker. private void ReceiveMessages(object sender, DoWorkEventArgs e) {     while (true)     {         // Receive a vote message from the queue         BrokeredMessage msg = ScatterGatherQueueClient.Receive();         if (msg != null)         {             // Deserialize the message.             Vote vote = msg.GetBody<Vote>();               // Update the results.             foreach (Result result in Results)             {                 if (result.Question.Equals(vote.QuestionText))                 {                     if (vote.IsYes)                     {                         result.YesVotes++;                     }                     else                     {                         result.NoVotes++;                     }                     break;                 }             }               // Mark the message as complete.             msg.Complete();         }       } }     When a vote message is received, the result that matches the vote question is updated with the vote from the user. The message is then marked as complete. A second background thread is used to update the display of subscriptions in the TreeView, with a dispatcher used to update the user interface. // This runs on a background worker. private void UpdateSubscriptions(object sender, DoWorkEventArgs e) {     while (true)     {         // Get a list of subscriptions.         IEnumerable<SubscriptionDescription> subscriptions =             NamespaceManager.GetSubscriptions(AccountDetails.ScatterGatherTopic);           // Update the user interface.         SimpleDelegate setQuestion = delegate()         {             trvSubscriptions.Items.Clear();             TreeViewItem topicItem = new TreeViewItem()             {                 Header = AccountDetails.ScatterGatherTopic             };               foreach (SubscriptionDescription subscription in subscriptions)             {                 TreeViewItem subscriptionItem = new TreeViewItem()                 {                     Header = subscription.Name                 };                 topicItem.Items.Add(subscriptionItem);             }             trvSubscriptions.Items.Add(topicItem);               topicItem.ExpandSubtree();         };         this.Dispatcher.BeginInvoke(DispatcherPriority.Send, setQuestion);           Thread.Sleep(3000);     } }       Voting Application The voting application is implemented as another WPF application. This one is more basic, and allows the user to vote “Yes” or “No” for the questions sent by the poll manager application. The user interface for that application is shown below. When an instance of the voting application is created it will create a subscription in the questions topic using a GUID as the subscription name. The application can then receive copies of every question message that is sent to the topic. Clients for the new subscription and the votes queue are created, along with a background worker to receive the question messages. The voting application is set to receiving mode, meaning it is ready to receive a question message from the subscription.   public MainWindow() {     InitializeComponent();       // Set the mode to receiving.     IsReceiving = true;       // Create a token provider with the relevant credentials.     TokenProvider credentials =         TokenProvider.CreateSharedSecretTokenProvider         (AccountDetails.Name, AccountDetails.Key);       // Create a URI for the serivce bus.     Uri serviceBusUri = ServiceBusEnvironment.CreateServiceUri         ("sb", AccountDetails.Namespace, string.Empty);       // Create the MessagingFactory     MessagingFactory factory = MessagingFactory.Create(serviceBusUri, credentials);       // Create a subcription for this instance     NamespaceManager mgr = new NamespaceManager(serviceBusUri, credentials);     string subscriptionName = Guid.NewGuid().ToString();     mgr.CreateSubscription(AccountDetails.ScatterGatherTopic, subscriptionName);       // Create the subscription and queue clients.     ScatterGatherSubscriptionClient = factory.CreateSubscriptionClient         (AccountDetails.ScatterGatherTopic, subscriptionName);     ScatterGatherQueueClient =         factory.CreateQueueClient(AccountDetails.ScatterGatherQueue);       // Start the background worker thread.     BackgroundWorker = new BackgroundWorker();     BackgroundWorker.DoWork += new DoWorkEventHandler(ReceiveMessages);     BackgroundWorker.RunWorkerAsync(); }     I took the inspiration for creating the subscriptions in the voting application from the chat application that uses topics and subscriptions blogged by Ovais Akhter here. The method that receives the question messages runs on a background thread. If the application is in receive mode, a question message will be received from the subscription, the question will be displayed in the user interface, the voting buttons enabled, and IsReceiving set to false to prevent more questing from being received before the current one is answered.   // This runs on a background worker. private void ReceiveMessages(object sender, DoWorkEventArgs e) {     while (true)     {         if (IsReceiving)         {             // Receive a question message from the topic.             BrokeredMessage msg = ScatterGatherSubscriptionClient.Receive();             if (msg != null)             {                 // Deserialize the message.                 Question question = msg.GetBody<Question>();                   // Update the user interface.                 SimpleDelegate setQuestion = delegate()                 {                     lblQuestion.Content = question.QuestionText;                     btnYes.IsEnabled = true;                     btnNo.IsEnabled = true;                 };                 this.Dispatcher.BeginInvoke(DispatcherPriority.Send, setQuestion);                 IsReceiving = false;                   // Mark the message as complete.                 msg.Complete();             }         }         else         {             Thread.Sleep(1000);         }     } }     When the user clicks on the Yes or No button, the btnVote_Click method is called. This will create a new Vote data contract with the appropriate question and answer and send the message to the poll manager application using the votes queue. The user voting buttons are then disabled, the question text cleared, and the IsReceiving flag set to true to allow a new message to be received.   private void btnVote_Click(object sender, RoutedEventArgs e) {     // Create a new vote.     Vote vote = new Vote()     {         QuestionText = (string)lblQuestion.Content,         IsYes = ((sender as Button).Content as string).Equals("Yes")     };       // Send the vote message.     BrokeredMessage msg = new BrokeredMessage(vote);     ScatterGatherQueueClient.Send(msg);       // Update the user interface.     lblQuestion.Content = "";     btnYes.IsEnabled = false;     btnNo.IsEnabled = false;     IsReceiving = true; }     Testing the Application In order to test the application, an instance of the poll manager application is started; the user interface is shown below. As no instances of the voting application have been created there are no subscriptions present in the topic. When an instance of the voting application is created the subscription will be displayed in the poll manager. Now that a voting application is subscribing, a questing can be sent from the poll manager application. When the message is sent to the topic, the voting application will receive the message and display the question. The voter can then answer the question by clicking on the appropriate button. The results of the vote are updated in the poll manager application. When two more instances of the voting application are created, the poll manager will display the new subscriptions. More questions can then be broadcast to the voting applications. As the question messages are queued up in the subscription for each voting application, the users can answer the questions in their own time. The vote messages will be received by the poll manager application and aggregated to display the results. The screenshots of the applications part way through voting are shown below. The messages for each voting application are queued up in sequence on the voting application subscriptions, allowing the questions to be answered at different speeds by the voters.

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  • MySql: Query multiple identical dynamic tables.

    - by JYelton
    I have a database with 500+ tables, each with identical structure, that contain historical data from sensors. I am trying to come up with a query that will locate, for example, all instances where sensor n exceeds x. The problem is that the tables are dynamic, the query must be able to dynamically obtain the list of tables. I can query information_schema.tables to get a list of the tables, like so: SELECT table_name FROM information_schema.tables WHERE table_schema = 'database_name'; I can use this to create a loop in the program and then query the database repeatedly, however it seems like there should be a way to have MySql do the multiple table search. I have not been able to make a stored procedure that works, but the examples I can find are generally for searching for a string in any column. I want to specifically find data in a specific column that exists in all tables. I admit I do not understand how to properly use stored procedures nor if they are the appropriate solution to this problem. An example query inside the loop would be: SELECT device_name, sensor_value FROM device_table WHERE sensor_value > 10; Trying the following does not work: SELECT device_name, sensor_value FROM ( SELECT table_name FROM information_schema.tables WHERE table_schema = 'database_name' ) WHERE sensor_value > 10; It results in an error: "Every derived table must have its own alias." The goal is to have a list of all devices that have had a given sensor value occur anywhere in their log (table). Ultimately, should I just loop in my program once I've obtained a list of tables, or is there a query structure that would be more efficient?

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  • Is there a Distributed SAN/Storage System out there?

    - by Joel Coel
    Like many other places, we ask our users not to save files to their local machines. Instead, we encourage that they be put on a file server so that others (with appropriate permissions) can use them and that the files are backed up properly. The result of this is that most users have large hard drives that are sitting mainly empty. It's 2010 now. Surely there is a system out there that lets you turn that empty space into a virtual SAN or document library? What I envision is a client program that is pushed out to users' PCs that coordinates with a central server. The server looks to users just like a normal file server, but instead of keeping entire file contents it merely keeps a record of where those files can be found among various user PCs. It then coordinates with the right clients to serve up file requests. The client software would be able to respond to such requests directly, as well as be smart enough to cache recent files locally. For redundancy the server could make sure files are copied to multiple PCs, perhaps allowing you to define groups in different locations so that an instance of the entire repository lives in each group to protect against a disaster in one building taking down everything else. Obviously you wouldn't point your database server here, but for simpler things I see several advantages: Files can often be transferred from a nearer machine. Disk space grows automatically as your company does. Should ultimately be cheaper, as you don't need to keep a separate set of disks I can see a few downsides as well: Occasional degradation of user pc performance, if the machine has to serve or accept a large file transfer during a busy period. Writes have to be propogated around the network several times (though I suspect this isn't really much of a problem, as reading happens in most places more than writing) Still need a way to send a complete copy of the data offsite occasionally, and this would make it very hard to do differentials Think of this like a cloud storage system that lives entirely within your corporate LAN and makes use of your existing user equipment. Our old main file server is due for retirement in about 2 years, and I'm looking into replacing it with a small SAN. I'm thinking something like this would be a better fit. As a school, we have a couple computer labs I can leave running that would be perfect for adding a little extra redundancy to the system. Unfortunately, the closest thing I can find is Dienst, and it's just a paper that dates back to 1994. Am I just using the wrong buzzwords in my searches, or does this really not exist? If not, is there a big downside that I'm missing?

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  • Azure &ndash; Part 6 &ndash; Blob Storage Service

    - by Shaun
    When migrate your application onto the Azure one of the biggest concern would be the external files. In the original way we understood and ensure which machine and folder our application (website or web service) is located in. So that we can use the MapPath or some other methods to read and write the external files for example the images, text files or the xml files, etc. But things have been changed when we deploy them on Azure. Azure is not a server, or a single machine, it’s a set of virtual server machine running under the Azure OS. And even worse, your application might be moved between thses machines. So it’s impossible to read or write the external files on Azure. In order to resolve this issue the Windows Azure provides another storage serviec – Blob, for us. Different to the table service, the blob serivce is to be used to store text and binary data rather than the structured data. It provides two types of blobs: Block Blobs and Page Blobs. Block Blobs are optimized for streaming. They are comprised of blocks, each of which is identified by a block ID and each block can be a maximum of 4 MB in size. Page Blobs are are optimized for random read/write operations and provide the ability to write to a range of bytes in a blob. They are a collection of pages. The maximum size for a page blob is 1 TB.   In the managed library the Azure SDK allows us to communicate with the blobs through these classes CloudBlobClient, CloudBlobContainer, CloudBlockBlob and the CloudPageBlob. Similar with the table service managed library, the CloudBlobClient allows us to reach the blob service by passing our storage account information and also responsible for creating the blob container is not exist. Then from the CloudBlobContainer we can save or load the block blobs and page blobs into the CloudBlockBlob and the CloudPageBlob classes.   Let’s improve our exmaple in the previous posts – add a service method allows the user to upload the logo image. In the server side I created a method name UploadLogo with 2 parameters: email and image. Then I created the storage account from the config file. I also add the validation to ensure that the email passed in is valid. 1: var storageAccount = CloudStorageAccount.FromConfigurationSetting("DataConnectionString"); 2: var accountContext = new DynamicDataContext<Account>(storageAccount); 3:  4: // validation 5: var accountNumber = accountContext.Load() 6: .Where(a => a.Email == email) 7: .ToList() 8: .Count; 9: if (accountNumber <= 0) 10: { 11: throw new ApplicationException(string.Format("Cannot find the account with the email {0}.", email)); 12: } Then there are three steps for saving the image into the blob service. First alike the table service I created the container with a unique name and create it if it’s not exist. 1: // create the blob container for account logos if not exist 2: CloudBlobClient blobStorage = storageAccount.CreateCloudBlobClient(); 3: CloudBlobContainer container = blobStorage.GetContainerReference("account-logo"); 4: container.CreateIfNotExist(); Then, since in this example I will just send the blob access URL back to the client so I need to open the read permission on that container. 1: // configure blob container for public access 2: BlobContainerPermissions permissions = container.GetPermissions(); 3: permissions.PublicAccess = BlobContainerPublicAccessType.Container; 4: container.SetPermissions(permissions); And at the end I combine the blob resource name from the input file name and Guid, and then save it to the block blob by using the UploadByteArray method. Finally I returned the URL of this blob back to the client side. 1: // save the blob into the blob service 2: string uniqueBlobName = string.Format("{0}_{1}.jpg", email, Guid.NewGuid().ToString()); 3: CloudBlockBlob blob = container.GetBlockBlobReference(uniqueBlobName); 4: blob.UploadByteArray(image); 5:  6: return blob.Uri.ToString(); Let’s update a bit on the client side application and see the result. Here I just use my simple console application to let the user input the email and the file name of the image. If it’s OK it will show the URL of the blob on the server side so that we can see it through the web browser. Then we can see the logo I’ve just uploaded through the URL here. You may notice that the blob URL was based on the container name and the blob unique name. In the document of the Azure SDK there’s a page for the rule of naming them, but I think the simple rule would be – they must be valid as an URL address. So that you cannot name the container with dot or slash as it will break the ADO.Data Service routing rule. For exmaple if you named the blob container as Account.Logo then it will throw an exception says 400 Bad Request.   Summary In this short entity I covered the simple usage of the blob service to save the images onto Azure. Since the Azure platform does not support the file system we have to migrate our code for reading/writing files to the blob service before deploy it to Azure. In order to reducing this effort Microsoft provided a new approch named Drive, which allows us read and write the NTFS files just likes what we did before. It’s built up on the blob serivce but more properly for files accessing. I will discuss more about it in the next post.   Hope this helps, Shaun All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

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