performance measurement - Page 8

high performance with xen, vmware or virtualbox

- by Marchosius

I was wondering which is the best method to go about if I want to play win based games. I do not want to go with the dual boot method as this will cost me time to restart, login and run a os to do my work or pass the time, and some of my apps rely on win and my graphics to run. for example Daz3d, Photoshop, Flash etc. Now I read about HVM(hardware virtual machines) and then I know about the 3D virtualisation of VMware and VirtualBox. How ever the 2 later virtualise the 3D not using the full power of the GPU. So this option wont perform perfect for latest games like D3. I was wondering if anyone have experience in HVM(like xen if i am not mistaken) and tried something similar to access the full power of the GPU and successfully run newer games and other products relying on the GPU? Will be the first time setting up a HVM, no experience in this so don't know what to expect. This will help a lot as I do not want to revert back to win or as mentioned do dual boot.

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IOS OpenGl transparency performance issue

- by user346443

I have built a game in Unity that uses OpenGL ES 1.1 for IOS. I have a nice constant frame rate of 30 until i place a semi transparent texture over the top on my entire scene. I expect the drop in frames is due to the blending overhead with sorting the frame buffer. On 4s and 3gs the frames stay at 30 but on the iPhone 4 the frame rate drops to 15-20. Probably due to the extra pixels in the retina compared to the 3gs and smaller cpu/gpu compared to the 4s. I would like to know if there is anything i can do to try and increase the frame rate when a transparent texture is rendered on top of the entire scene. Please not the the transparent texture overlay is a core part of the game and i can't disable anything else in the scene to speed things up. If its guaranteed to make a difference I guess I can switch to OpenGl ES 2.0 and write the shaders but i would prefer not to as i need to target older devices. I should add that the depth buffer is disabled and I'm blending using SrcAlpha One. Any advice would be highly appreciated. Cheers

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Slow Firefox Javascript Canvas Performance?

- by jujumbura

As a followup from a previous post, I have been trying to track down some slowdown I am having when drawing a scene using Javascript and the canvas element. I decided to narrow down my focus to a REALLY barebones animation that only clears the canvas and draws a single image, once per-frame. This of course runs silky smooth in Chrome, but it still stutters in Firefox. I added a simple FPS calculator, and indeed it appears that my page is typically getting an FPS in the 50's when running Firefox. This doesn't seem right to me, I must be doing something wrong here. Can anybody see anything I might be doing that is causing this drop in FPS? <!DOCTYPE HTML> <html> <head> </head> <body bgcolor=silver> <canvas id="myCanvas" width="600" height="400"></canvas> <img id="myHexagon" src="Images/Hexagon.png" style="display: none;"> <script> window.requestAnimFrame = (function(callback) { return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame || function(callback) { window.setTimeout(callback, 1000 / 60); }; })(); var animX = 0; var frameCounter = 0; var fps = 0; var time = new Date(); function animate() { var canvas = document.getElementById("myCanvas"); var context = canvas.getContext("2d"); context.clearRect(0, 0, canvas.width, canvas.height); animX += 1; if (animX == canvas.width) { animX = 0; } var image = document.getElementById("myHexagon"); context.drawImage(image, animX, 128); context.lineWidth=1; context.fillStyle="#000000"; context.lineStyle="#ffffff"; context.font="18px sans-serif"; context.fillText("fps: " + fps, 20, 20); ++frameCounter; var currentTime = new Date(); var elapsedTimeMS = currentTime - time; if (elapsedTimeMS >= 1000) { fps = frameCounter; frameCounter = 0; time = currentTime; } // request new frame requestAnimFrame(function() { animate(); }); } window.onload = function() { animate(); }; </script> </body> </html>

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Fresh install 12.04 Performance & Stability: SONY VPCCW2S1E

- by George Katsanos

just yesterday I installed 12.04. Is it normal that installing a package (Chrome for example) takes 5 to 10 minutes (compared to Windows 7 for example which takes 2 or 3)? (with end result: installation failed) Otherwise is it normal that while the system is doing some installation,extracting packs and so on, other applications often become unresponsive? Sidenote: I don't care about fancy desktop effects, I installed ubuntu to go on and experiment with web servers, memcache, Varnish and git/svn. So basically I plan to do lots of console-only operations. My surprise was also the difference of stability compared to an old FreeBSD installation I had on a dinosaur P3 550Mhz :) (I am on a SONY VPCCW2S1E) (I guess it might have to do something with my problems?)

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Website performance tips?

- by Michael Schinis

Im kind of having some troubles with the loading of my website: Here's a link to the website: link It sometimes loads fast, then when you refresh it.. most of the times, it will just keep trying to load images, and keep doing that for a minute or so, and none of the javascript will execute. I have followed most of the tips given by yahoo, except caching, which I couldn't get working properly. Does anyone know how to do proper caching of image and javascript files using htaccess? most of the code I found online won't work. Any advice whatsoever is extremely helpful. Thanks

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Google bots are severely affecting site performance

- by Lynn

I have an aggregate site on a linux server that pulls in feeds from a universe of about 2,000 blogs. It's in Wordpress 3.4.2 and I have a cron job that is staggered to run five times an hour on another server to pull in the stories and then publish them to the front page of this site. This is so I didn't put too much pressure all on one server. However, the Google bots, which visit a few times every hour bring the server to its knees in the morning and evenings when there is an increase in traffic on the site. The bots have something like 30,000 links to follow at this point. How do I throttle the bots to simply grab the new stories off the front page and stop there? EDIT- Details of my server configuration: The way we have this set up is the server that handles all the publishing is an unmanaged instance via AWS. It mounts the NFS server and connects to the RDS to update content, etc. You get to this publishing instance via a plugin that detects the wp-admin link and then redirects you into there. The front end app server also mounts the NFS and requests data from the RDS. It is the only one that has the WP Super Cache on it.... The OS is Ubuntu on the App server and the NFS runs CentOs. The front end is Nginx and the publishing server is Apache.

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Ubuntu with KDE and kernel 3.6.2 - performance issues

- by Pelda

I have recently swiched to Ubuntu and installed KDe on it. I like software included in Ubuntu but interface from Kubuntu. My problem is, that after installation of kernel 3.6.2 (deafult ubuntu 12.04 is 3.2 I think) - whole KDE interface is laggy and I have to render using Xrended because Opel AL doesnt work. So please tell me - I didint find it anywhere - Does KDE has some problems with new kernel? should i downgrade back to 3.x.x? Thank you for answers and your time. Pelda

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DDD Model Design and Repository Persistence Performance Considerations

- by agarhy

So I have been reading about DDD for some time and trying to figure out the best approach on several issues. I tend to agree that I should design my model in a persistent agnostic manner. And that repositories should load and persist my models in valid states. But are these approaches realistic practically? I mean its normal for a model to hold a reference to a collection of another type. Persisting that model should mean persist the entire collection. Fine. But do I really need to load the entire collection every time I load the model? Probably not. So I can have specialized repositories. Some that load maybe a subset of the object graph via DTOs and others that load the entire object graph. But when do I use which? If I have DTOs, what's stopping client code from directly calling them and completely bypassing the model? I can have mappers and factories to create my models from DTOs maybe? But depending on the design of my models that might not always work. Or it might not allow my models to be created in a valid state. What's the correct approach here?

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Optimizing hash lookup & memory performance in Go

- by Moishe

As an exercise, I'm implementing HashLife in Go. In brief, HashLife works by memoizing nodes in a quadtree so that once a given node's value in the future has been calculated, it can just be looked up instead of being re-calculated. So eg. if you have a node at the 8x8 level, you remember it by its four children (each at the 2x2 level). So next time you see an 8x8 node, when you calculate the next generation, you first check if you've already seen a node with those same four children. This is extended up through all levels of the quadtree, which gives you some pretty amazing optimizations if eg. you're 10 levels above the leaves. Unsurprisingly, it looks like the perfmance crux of this is the lookup of nodes by child-node values. Currently I have a hashmap of {&upper_left_node,&upper_right_node,&lower_left_node,&lower_right_node} -> node So my lookup function is this: func FindNode(ul, ur, ll, lr *Node) *Node { var node *Node var ok bool nc := NodeChildren{ul, ur, ll, lr} node, ok = NodeMap[nc] if ok { return node } node = &Node{ul, ur, ll, lr, 0, ul.Level + 1, nil} NodeMap[nc] = node return node } What I'm trying to figure out is if the "nc := NodeChildren..." line causes a memory allocation each time the function is called. If it does, can I/should I move the declaration to the global scope and just modify the values each time this function is called? Or is there a more efficient way to do this? Any advice/feedback would be welcome. (even coding style nits; this is literally the first thing I've written in Go so I'd love any feedback)

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Performance cost of running Ubuntu from external hard drive

- by dandan78

A friend just complained to me about Ubuntu being slow. Although I've noticed a certain lack of snappiness with Linux vs Windows in the past, I really can't say I've had much to grumble about with the recent distributions of Ubuntu. That said, his objections seem much worse than the ones I used to have and I know that his current setup is significantly more powerful than my laptop. And then it turned out he is running Ubuntu off an external HDD hooked up via USB2.0. The HD enclosure is USB3.0 but apparently he can't manage to get it to boot on USB3.0 so he switched to one of the USB2.0 ports or whatever and that works, albeit not very well. Now I would expect USB to add some overhead to communication between the computer and the HDD; SATA is after all designed to get the maximum out of a hard drive, whereas USB is, well, universal. What are your expreriences with booting off external HDDs? Edit: Does anybody know just how much of a slowdown can be expected?

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AWR Performance Report and Read by Other Session Waits

- by user702295

For the questions regarding "read by other session" and its relation to "db file sequential/scattered read", the logic is like this: When a "db file sequential/scattered read" is done, the blocks are either already in the cache or on the disk. Since any operation on blocks is done in the cache and since and the issue is "read by other session" I will relate to the case the blocks are on the disk. Process A is reading the needed block from the disk to the cache. During that time, if process B (and C and others) need the same block, it will wait on "read by other session". A and B can be threads of the same process running in parallel or unrelated processes. For example two processes doing full table scan on mdp_matrix etc. Solutions for that can be lowering the number of processes competing on the same blocks, increasing PCTFREE. If it is a full table scan, maybe an index is missing that can result in less blocks being read from the cache and so on.

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Pain of the Week/Expert's Perspective: Performance Tuning for Backups and Restores

- by KKline

First off - the Pain of the Week webcast series has been renamed. It's now known as The Expert's Perspective . Please join us for future webcasts and, if you're interested in speaking, drop me a note to see if we can get you on the roster! The bigger your databases get, the longer backups take. That doesn't really seem like a huge problem — until disaster strikes and you need to restore your databases as fast as possible. Join my buddy Brent Ozar ( blog | twitter ), a Microsoft Certified Master of...(read more)

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Intel programming "performance" books? [closed]

- by user997112

I vaguely remember seeing that Intel have produced a few good books, especially with regards to low latency programming, but I cannot remember the titles. Could people suggest the titles of Intel books (or ones relating to Intel products)? Examples include books on: -Intel Compiler -Intel Assembler -Any low level programming on Intel assembler -The Intel CPU architecture -Intel threading blocks library

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Displaying performance data per engine subsystem

- by liortal

Our game (Android based) traces how long it takes to do the world logic updates, and how long it takes to a render a frame to the device screen. These traces are collected every frame, and displayed at a constant interval (currently every 1 second). I've seen games where on-screen data of various engine subsystems is displayed, with the time they consume (either in text) or as horizontal colored bars. I am wondering how to implement such a feature?

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Practical RAID Performance?

- by wag2639

I've always thought the following to be a general rule of thumb for RAID: RAID 0: Best performance for READ and WRITE from stripping, greatest risk RAID 1: Redundant, decent for READ (I believe it can read from different parts of a file from different hard drives), not the best for WRITE RAID 0+1 (01): combines redundancy of RAID 1 with performance of RAID 0 RAID 1+0 (10): slightly better version of RAID 0+1 RAID 5: good READ performance, bad WRITE performance, redundant IS THIS ASSUMPTION CORRECT? (and how do they compare to a JBOD setup for R/W IO performance) Are certain practical RAID setups better for different applications: gaming, video editing, database (Acccess or SQL)? I was thinking about hard disk drives but does this apply to solid state drives as well?

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OpenVZ vs Xen, how much difference in performance?

- by Aleksandr Levchuk

There is a Xen vs. KVM in performance question on ServerFault. What will be the performance difference if the choice is between Xen and OpenVZ? How is it best to measure? Some may say "you're comparing apples and oranges" but I have to choose one of the two and it needs to be wise choice. Performance is most important to us. We may switching to Xen from OpenVZ because Xen is more ubiquitous but only if performance difference is not significant. In January 2011 I'm thinking of doing a head to head performance comparison - here is my project proposal to our Bioinformatics facility director.

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SQL SERVER – Transcript of Learning SQL Server Performance: Indexing Basics – Interview of Vinod Kumar by Pinal Dave

- by pinaldave

Recently I just wrote a blog post on about Learning SQL Server Performance: Indexing Basics and I received lots of request that if we can share some insight into the course. Here is 200 seconds interview of Vinod Kumar I took right after completing the course. We have few free codes to watch the course, please your comment at http://facebook.com/SQLAuth and we will few of first ones, we will send the code. There are many people who said they would like to read the transcript of the video. Here I have generated the same. Pinal: Vinod, we recently released this course, SQL Server Indexing. It is about performance tuning. So tell me – how do indexes help performance? Vinod: I think what happens in the industry when it comes to performance is that developers and DBAs look at indexes first. So that’s the first step for any performance tuning exercise, indexing is one of the most critical aspects and it is important to learn it the right way. Pinal: Correct. So what you mean to say is that if you know indexing you can pretty much tune any server and query. Vinod: So I might contradict my false statement now. Indexing is usually a stepping stone but it does not lead you to the end. But it’s good to start with indexing and there are lots of nuances to indexing that you need to understand, like how SQL uses indexing and how performance can improve because of the strategies that you have made. Pinal: But now I’m confused. First you said indexes are good, and then you said that indexes can degrade your performance. So what is this course about? I mean how does this course really make an impact? Vinod: Ok -so from the course perspective, what we are trying to do is give you a capsule which gives you a good start. Every journey needs a beginning, you need that first step. This course is that first step in understanding. This is the most basic, fundamental course that we have tried to attack. This is the fundamentals of indexing, some of the key things that you must know about indexing. Some of the basics of indexing are lesser known and so I think this course is geared towards each and every one of you out there who wants to understand little bit more about indexing. Pinal: So what I understand is that if I enrolled in this course I will have a minimum understanding about indexing when dealing with performance tuning. Right? Vinod: Exactly. In this course is we have tried to give you a nice summary. We are talking about clustered indexing, non clustered indexing, too many indexes, too few indexes, over indexing, under indexing, duplicate indexing, columns tune indexing, with SQL Server 2012. There’s lot’s to learn. Pinal: You can see the URL [http://bit.ly/sql-index] of the course on the screen. Go ahead, attend, and let us know what you think about it. Thank you. Vinod: Thank you. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Index, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology, Video

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Are there any solutions for translating measurement units on Rails?

- by Leonid Shevtsov

I'd like to implement measurement unit preferences in a Ruby on Rails app. For instance, the user should be able to select between displaying distances in miles or in kilometers. And, obviously, not only displaying, but entering values, too. I suppose all values should be stored in one global measurement system to simplify calculations. Are there any drop-in solutions for this? Or should I maybe write my own?

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How does a website latency simulator work

- by nighthawk457

Sites like webpagetest allow users to enter a website url and a test location, to run a speed test on the site from multiple locations using real browsers. Can anyone give me a basic idea of how sites like this work? You also have plugin's like Aptimize latency simulator or charles web debugging proxy app, that simulate the delay while accessing a site from different locations. I am assuming since these are plugin's these function in a different way. How do these plugin's work ?

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How to test the render speed of my solution in a web browser?

- by Cuartico

Ok, I need to test the speed of my solution in a web browser, but I have some problems, there are 2 versions of the web solution, the original one that is on server A and the "fixed" version that is on server B. I have VS2010 Ultimate, so I can make a web and load test on solution B, but I can't load the A solution on my IDE. I was trying to use fiddle2 and jmeter, but they only gave me the times of the request and response of the browsers with the server, I also want the time it takes to the browser to render the whole page. Maybe I'm misusing some of this tools... I don't know if this could be usefull but: Solution A is on VB 6.0 Solution B is on VB.Net Thanks in advance!

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Social media measurement tools [on hold]

- by user29187

I work for a non-profit and we are currently trying to develop a system to measure and evaluate our social media platforms (Facebook and Twitter). We would liek to tarck a variety of social metrics, including, but not limited to: Twitter: # of followers, # of mentions, # of retweets Facebook: # of likes, # people talking about, # of page views We are currently using a paid platform for this. I wondered if there is a way to configure Google Analytics to do this or if there are any other free/clever or smart ways to track social engagement with our brand?

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Strategy to use two different measurement systems in software

- by Dennis

I have an application that needs to accept and output values in both US Custom Units and Metric system. Right now the conversion and input and output is a mess. You can only enter in US system, but you can choose the output to be US or Metric, and the code to do the conversions is everywhere. So I want to organize this and put together some simple rules. So I came up with this: Rules user can enter values in either US or Metric, and User Interface will take care of marking this properly All units internally will be stored as US, since the majority of the system already has most of the data stored like that and depends on this. It shouldn't matter I suppose as long as you don't mix unit. All output will be in US or Metric, depending on user selection/choice/preference. In theory this sounds great and seems like a solution. However, one little problem I came across is this: There is some data stored in code or in the database that already returns data like this: 4 x 13/16" screws, which means "four times screws". I need the to be in either US or Metric. Where exactly do I put the conversion code for doing the conversion for this unit? The above already mixing presentation and data, but the data for the field I need to populate is that whole string. I can certainly split it up into the number 4, the 13/16", and the " x " and the " screws", but the question remains... where do I put the conversion code? Different Locations for Conversion Routines 1) Right now the string is in a class where it's produced. I can put conversion code right into that class and it may be a good solution. Except then, I want to be consistent so I will be putting conversion procedures everywhere in the code at-data-source, or right after reading it from the database. The problem though is I think that my code will have to deal with two systems, all throughout the codebase after this, should I do this. 2) According to the rules, my idea was to put it in the view script, aka last change to modify it before it is shown to the user. And it may be the right thing to do, but then it strikes me it may not always be the best solution. (First, it complicates the view script a tad, second, I need to do more work on the data side to split things up more, or do extra parsing, such as in my case above). 3) Another solution is to do this somewhere in the data prep step before the view, aka somewhere in the middle, before the view, but after the data-source. This strikes me as messy and that could be the reason why my codebase is in such a mess right now. It seems that there is no best solution. What do I do?

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Logic - Time measurement

- by user73384

To measure the following for tasks- Last execution time and maximum execution time for each task. CPU load/time consumed by each task over a defined period informed by application at run time. Maximum CPU load consumed by each task. Tasks have following characteristics- First task runs as background – Event information for entering only Second task - periodic – Event information for entering and exiting from task Third task is interrupt , can start any time – no information available from this task Forth task highest priority interrupt , can start any time – Event information for entering and exiting from task Should use least possible execution time and memory. 32bit increment timer available for time counting. Lets prepare and discuss the logic, It’s OK to have limitations …! Questions on understanding problem statement are welcome

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Oracle TimesTen In-Memory Database Performance on SPARC T4-2

- by Brian

The Oracle TimesTen In-Memory Database is optimized to run on Oracle's SPARC T4 processor platforms running Oracle Solaris 11 providing unsurpassed scalability, performance, upgradability, protection of investment and return on investment. The following demonstrate the value of combining Oracle TimesTen In-Memory Database with SPARC T4 servers and Oracle Solaris 11: On a Mobile Call Processing test, the 2-socket SPARC T4-2 server outperforms: Oracle's SPARC Enterprise M4000 server (4 x 2.66 GHz SPARC64 VII+) by 34%. Oracle's SPARC T3-4 (4 x 1.65 GHz SPARC T3) by 2.7x, or 5.4x per processor. Utilizing the TimesTen Performance Throughput Benchmark (TPTBM), the SPARC T4-2 server protects investments with: 2.1x the overall performance of a 4-socket SPARC Enterprise M4000 server in read-only mode and 1.5x the performance in update-only testing. This is 4.2x more performance per processor than the SPARC64 VII+ 2.66 GHz based system. 10x more performance per processor than the SPARC T2+ 1.4 GHz server. 1.6x better performance per processor than the SPARC T3 1.65 GHz based server. In replication testing, the two socket SPARC T4-2 server is over 3x faster than the performance of a four socket SPARC Enterprise T5440 server in both asynchronous replication environment and the highly available 2-Safe replication. This testing emphasizes parallel replication between systems. Performance Landscape Mobile Call Processing Test Performance System Processor Sockets/Cores/Threads Tps SPARC T4-2 SPARC T4, 2.85 GHz 2 16 128 218,400 M4000 SPARC64 VII+, 2.66 GHz 4 16 32 162,900 SPARC T3-4 SPARC T3, 1.65 GHz 4 64 512 80,400 TimesTen Performance Throughput Benchmark (TPTBM) Read-Only System Processor Sockets/Cores/Threads Tps SPARC T3-4 SPARC T3, 1.65 GHz 4 64 512 7.9M SPARC T4-2 SPARC T4, 2.85 GHz 2 16 128 6.5M M4000 SPARC64 VII+, 2.66 GHz 4 16 32 3.1M T5440 SPARC T2+, 1.4 GHz 4 32 256 3.1M TimesTen Performance Throughput Benchmark (TPTBM) Update-Only System Processor Sockets/Cores/Threads Tps SPARC T4-2 SPARC T4, 2.85 GHz 2 16 128 547,800 M4000 SPARC64 VII+, 2.66 GHz 4 16 32 363,800 SPARC T3-4 SPARC T3, 1.65 GHz 4 64 512 240,500 TimesTen Replication Tests System Processor Sockets/Cores/Threads Asynchronous 2-Safe SPARC T4-2 SPARC T4, 2.85 GHz 2 16 128 38,024 13,701 SPARC T5440 SPARC T2+, 1.4 GHz 4 32 256 11,621 4,615 Configuration Summary Hardware Configurations: SPARC T4-2 server 2 x SPARC T4 processors, 2.85 GHz 256 GB memory 1 x 8 Gbs FC Qlogic HBA 1 x 6 Gbs SAS HBA 4 x 300 GB internal disks Sun Storage F5100 Flash Array (40 x 24 GB flash modules) 1 x Sun Fire X4275 server configured as COMSTAR head SPARC T3-4 server 4 x SPARC T3 processors, 1.6 GHz 512 GB memory 1 x 8 Gbs FC Qlogic HBA 8 x 146 GB internal disks 1 x Sun Fire X4275 server configured as COMSTAR head SPARC Enterprise M4000 server 4 x SPARC64 VII+ processors, 2.66 GHz 128 GB memory 1 x 8 Gbs FC Qlogic HBA 1 x 6 Gbs SAS HBA 2 x 146 GB internal disks Sun Storage F5100 Flash Array (40 x 24 GB flash modules) 1 x Sun Fire X4275 server configured as COMSTAR head Software Configuration: Oracle Solaris 11 11/11 Oracle TimesTen 11.2.2.4 Benchmark Descriptions TimesTen Performance Throughput BenchMark (TPTBM) is shipped with TimesTen and measures the total throughput of the system. The workload can test read-only, update-only, delete and insert operations as required. Mobile Call Processing is a customer-based workload for processing calls made by mobile phone subscribers. The workload has a mixture of read-only, update, and insert-only transactions. The peak throughput performance is measured from multiple concurrent processes executing the transactions until a peak performance is reached via saturation of the available resources. Parallel Replication tests using both asynchronous and 2-Safe replication methods. For asynchronous replication, transactions are processed in batches to maximize the throughput capabilities of the replication server and network. In 2-Safe replication, also known as no data-loss or high availability, transactions are replicated between servers immediately emphasizing low latency. For both environments, performance is measured in the number of parallel replication servers and the maximum transactions-per-second for all concurrent processes. See Also SPARC T4-2 Server oracle.com OTN Oracle TimesTen In-Memory Database oracle.com OTN Oracle Solaris oracle.com OTN Oracle Database 11g Release 2 Enterprise Edition oracle.com OTN Disclosure Statement Copyright 2012, Oracle and/or its affiliates. All rights reserved. Oracle and Java are registered trademarks of Oracle and/or its affiliates. Other names may be trademarks of their respective owners. Results as of 1 October 2012.

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Strange performance issue with Dell R7610 and LSI 2208 RAID controller

- by GregC

Connecting controller to any of the three PCIe x16 slots yield choppy read performance around 750 MB/sec Lowly PCIe x4 slot yields steady 1.2 GB/sec read Given same files, same Windows Server 2008 R2 OS, same RAID6 24-disk Seagate ES.2 3TB array on LSI 9286-8e, same Dell R7610 Precision Workstation with A03 BIOS, same W5000 graphics card (no other cards), same settings etc. I see super-low CPU utilization in both cases. SiSoft Sandra reports x8 at 5GT/sec in x16 slot, and x4 at 5GT/sec in x4 slot, as expected. I'd like to be able to rely on the sheer speed of x16 slots. What gives? What can I try? Any ideas? Please assist Cross-posted from http://en.community.dell.com/support-forums/desktop/f/3514/t/19526990.aspx Follow-up information We did some more performance testing with reading from 8 SSDs, connected directly (without an expander chip). This means that both SAS cables were utilized. We saw nearly double performance, but it varied from run to run: {2.0, 1.8, 1.6, and 1.4 GB/sec were observed, then performance jumped back up to 2.0}. The SSD RAID0 tests were conducted in a x16 PCIe slot, all other variables kept the same. It seems to me that we were getting double the performance of HDD-based RAID6 array. Just for reference: maximum possible read burst speed over single channel of SAS 6Gb/sec is 570 MB/sec due to 8b/10b encoding and protocol limitations (SAS cable provides four such channels).

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