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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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• Resources for JVM Tuning

  - by portoalet

  Anybody knows a good book or two (or resources) for JVM Tuning? I am struggling to find any. I stumbled upon Apress Java EE 5 Performance Management and Optimization, but there was not much in there.

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• A Perspective on Database Performance Tuning

  Fundamentally, database performance tuning is done for two basic reasons, to reduce response time and to reduce resource usage, both of which can apply for any given situation. Julian Stuhler looks at database performance tuning, and why it remains one of the most important topics for any DBA, developer or systems administrator.

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• A Perspective on Database Performance Tuning

  Fundamentally, database performance tuning is done for two basic reasons, to reduce response time and to reduce resource usage, both of which can apply for any given situation. Julian Stuhler looks at database performance tuning, and why it remains one of the most important topics for any DBA, developer or systems administrator.

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• Brute Force Hardware versus Tuning

  - by jchang

  Every now and then, the question is asked “When will servers be powerful enough that performance tuning will not be necessary.” Sometimes I get the impression this was posed not on technical grounds, but rather that ISVs and CIOs don’t like performance specialists. Fortunately (for me) it does not appear that this will ever happen for two principal reasons: 1) hardware and tuning contribute in such completely different aspects that neither can be ignored, and 2) multi-core processors actually introduce...(read more)

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• oracle database performance tuning

  - by sunil

  hi all, Any one have complete database performance script please post Thanks for your time. sunil

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• SQL 2008 Database tuning advisor won't start

  - by Andrew Hancox

  For some reason I can't get DTA to connect to my development machine. It connects to a remote DB just fine but when I point it to my dev machine I get an error saying: Failed to initialize MSDB database for tuning (exit code: -1073741819). I'm pretty sure it's not a permissions issue since I've used profiler to capture what it's doing and all of the commands it's run so far look fine and are being run under my account which is associated with the sysadmin role, when I run them in sql management studio they go through fine. I'm pretty convinced that the problem is related to creating the objects in MSDB that are used by DTA but I tried creating these manually (I found scripts on the web) and it just seems to push the problem along the line slightly. I'm going out of my mind - have even tried reinstalling SQL but that's not fixed it. I'm using SQL 2008 with SP1 (10.0.2531) on windows server 2008 (patched up to date). SAVE ME!!!!!

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• iPhone openGLES performance tuning

  - by genesys

  Hey there! I'm trying now for quite a while to optimize the framerate of my game without really making progress. I'm running on the newest iPhone SDK and have a iPhone 3G 3.1.2 device. I invoke arround 150 drawcalls, rendering about 1900 Triangles in total (all objects are textured using two texturelayers and multitexturing. most textures come from the same textureAtlasTexture stored in pvrtc 2bpp compressed texture). This renders on my phone at arround 30 fps, which appears to me to be way too low for only 1900 triangles. I tried many things to optimize the performance, including batching together the objects, transforming the vertices on the CPU and rendering them in a single drawcall. this yelds 8 drawcalls (as oposed to 150 drawcalls), but performance is about the same (fps drop to arround 26fps) I'm using 32byte vertices stored in an interleaved array (12bytes position, 12bytes normals, 8bytes uv). I'm rendering triangleLists and the vertices are ordered in TriStrip order. I did some profiling but I don't really know how to interprete it. instruments-sampling using Instruments and Sampling yelds this result: http://neo.cycovery.com/instruments_sampling.gif telling me that a lot of time is spent in "mach_msg_trap". I googled for it and it seems this function is called in order to wait for some other things. But wait for what?? instruments-openGL instruments with the openGL module yelds this result: http://neo.cycovery.com/intstruments_openglES_debug.gif but here i have really no idea what those numbers are telling me shark profiling: profiling with shark didn't tell me much either: http://neo.cycovery.com/shark_profile_release.gif the largest number is 10%, spent by DrawTriangles - and the whole rest is spent in very small percentage functions Can anyone tell me what else I could do in order to figure out the bottleneck and could help me to interprete those profiling information? Thanks a lot!

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• SQL SERVER – A Successful Performance Tuning Seminar – Hyderabad – Nov 27-28, 2010 – Next Pune

  - by pinaldave

  My recent SQL Server Performance Tuning Seminar in Colombo was oversubscribed with total of 35 attendees. You can read the details over here SQLAuthority News – SQL Server Performance Optimizations Seminar – Grand Success – Colombo, Sri Lanka – Oct 4 – 5, 2010. I had recently completed another seminar in Hyderabad which was again blazing success. We had 25 attendees to the seminar and had wonderful time together. There is one thing very different between usual class room training and this seminar series. In this seminar series we go 100% demo oriented and real world scenario deep down. We do not talk usual theory talk-talk. The goal of this seminar to give anybody who attends a jump start and deep dive on the performance tuning subject. I will share many different examples and scenarios from my years of experience of performance tuning. The beginning of the second day is always interesting as I take attendees the server as example of the talk, and together we will attempt to identify the bottleneck and see if we can resolve the same. So far I have got excellent feedback on this unique session, where we pick database of the attendees and address the issues. I plan to do the same again in next sessions. The next Seminar is in Pune.I am very excited for the same. Date and Time: December 4-5, 2010. 10 AM to 6 PM The Pride Hotel 05, University Road, Shivaji Nagar, Pune – 411 005 Tel: 020 255 34567 Click here for the agenda of the seminar. Instead of writing more details, I will let the photos do the talk for latest Hyderabad Seminar. Hotel Amrutha Castle King Arthur's Court Pinal Presenting Seminar Pinal Presenting Seminar Seminar Attendees Pinal Presenting Seminar Group Photo of Hyderabad Seminar Attendees Seminar Support Staff - Nupur and Shaivi Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Training, SQLAuthority Author Visit, SQLAuthority News, T SQL, Technology

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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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• Tuning B2B Server Engine Threads in SOA Suite 11g

  - by Shub Lahiri, A-Team

  Background B2B 11g has a number of parameters that can be tweaked to tune the engine for handling high volumes of messages. These parameters are also known as B2B server properties and managed via the EM console.  This note highlights one aspect of the tuning exercise and describes the different threads, that can be configured to tune the performance of a B2B server. Symptoms The most common indicator of a B2B engine in need of a tuning is reflected in the constant build-up of messages in an internal JMS queue within the B2B server. It is called B2B_EVENT_QUEUE and can be monitored via the Weblogic server console. Whenever such a behaviour is seen, it usually results in general degradation of performance. Remedy There could be many contributing factors behind a B2B server's degradation of performance. However, one of the first places to tune the server from the out-of-the-box, default configuration is to change the number of internal engine threads allocated within the B2B server. Usually the default configuration for the B2B server engine threads is not suitable for high-volume of messaging loads. So, it is necessary to increase the counts for 3 types of such threads, by specifying the appropriate B2B server properties via the EM console, namely, Inbound - b2b.inboundThreadCount Outbound - b2b.outboundThreadCount Default - b2b.defaultThreadCount The function of these threads are fairly self-explanatory. In other words, the inbound threads process the inbound messages that are coming into the B2B server from an external endpoint. Similarly, the outbound threads processes the messages that are sent out from the B2B server. The default threads are responsible for certain B2B server-specific special tasks. In case the inbound and outbound thread counts are not specified, the default thread count also dictates the total number of inbound and outbound threads. As found in any tuning exercise, the optimisation of these threads is usually reached via an iterative process. The best working combination of the thread counts are directly related to the system infrastructure, traffic load and several other environmental factors.

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• Replacement of Outlooksoft (SAP BPC) with Oracle EPM at Brady Corporation

  Nigel Youell, Product Marketing Director, Enterprise Performance Management Applications at Oracle discusses with Joe Bittorf, Project Manager at Brady Corporation why and how they embarked on this major project to replace SAP BPC with Oracle's Enterprise Performance Management Solution. Joe covers the outstanding improvements they have achieved in their financial close process, how they worked with Oracle Partner Emerging Solutions and the current project to further improve their planning and budgeting processes.

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• Honing Performance Tuning Skills on MySQL

  - by Antoinette O'Sullivan

  Get hands-on experience with techniques for tuning a MySQL Server with the Authorized MySQL Performance Tuning course.  This course is designed for database administrators, database developers and system administrators who are responsible for managing, optimizing, and tuning a MySQL Server. You can follow this live instructor led training: From your desk. Choose from among the 800+ events on the live-virtual training schedule. In a classroom. A selection of events/locations listed below  Location  Date  Delivery Language  Prague, Czech Republic  1 October 2012  Czech  Warsaw, Poland  9 July 2012  Polish  London, UK  19 November 2012  English  Rome, Italy  23 October 2012  Italian  Lisbon, Portugal  17 September 2012  European Portugese  Aix-en-Provence, France  4 September 2012  French  Strasbourg, France  16 October 2012  French  Nieuwegein, Netherlands  3 September 2012  Dutch  Madrid, Spain  6 August 2012  Spanish  Mechelen, Belgium  1 October 2012  English  Riga, Latvia  10 December 2012  Latvian  Petaling Jaya, Malaysia  10 September 2012  English  Edmonton, Canada  27 August 2012  English  Vancouver, Canada  27 August 2012  English  Ottawa, Canada  26 November 2012  English  Toronto, Canada  26 November 2012  English  Montreal, Canada  26 November 2012  English  Mexico City, Mexico  9 July 2012  Spanish  Sao Paulo, Brazil  2 July 2012  Brazilian Portugese To find a virtual or in-class event that suits you, go or http://oracle.com/education and choose a course and delivery type in your location.  

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• Tokyo Cabinet Tuning Parameters

  - by user235478

  Hello, I have been trying to find a better Tokyo Cabinet (or Tokyo Tyrant) configuration for my application, but I don't know exactly how. I know what some parameters mean but I want to have a fine tuning control, so I need to know the impact of each one. The Tokyo documentation is really good but not at this point. Does any one can help me? Thanks. TCHDB -> *bool tchdbtune(TCHDB *hdb, int64_t bnum, int8_t apow, int8_t fpow, uint8_t opts);* How do I use: bnum, apow and fpow? TCBDB -> *bool tcbdbtune(TCBDB *bdb, int32_t lmemb, int32_t nmemb, int64_t bnum, int8_t apow, int8_t fpow, uint8_t opts);* How do I use: lmemb, nmemb, bnum, apow and fpow? TCFDB -> *bool tcfdbtune(TCFDB *fdb, int32_t width, int64_t limsiz);* How do I use: width and limsiz? Note: I am only putting this to get all types of database in the topic, this one is really simple. TCTDB -> *bool tctdbtune(TCTDB *tdb, int64_t bnum, int8_t apow, int8_t fpow, uint8_t opts);* How do I use: bnum, apow and fpow?

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• Need help in tuning a sql-query

  - by Viper

  Hello, i need some help to boost this SQL-Statement. The execution time is around 125ms. During the runtime of my program this sql (better: equally structured sqls for different tables) will be called 300.000 times. The average row count in the tables lies around 10.000.000 rows and new rows (updates/inserts) will be added with a timestamp each day. Data which are interesting for this particular export-program lies in the last 1-3 days. Maybe this is helpful for an index to create. The data i need is the current valid row for a given id and the forerunner datarow to get the updates (if exists). We use a Oracle 11g database and Dot.Net Framework 3.5 SQL-Statement to boost: select ID_SOMETHING, -- Number(12) ID_CONTRIBUTOR, -- Char(4 Byte) DATE_VALID_FROM, -- DATE DATE_VALID_TO -- DATE from TBL_SOMETHING XID where ID_SOMETHING = :ID_INSTRUMENT and ID_CONTRIBUTOR = :ID_CONTRIBUTOR and DATE_VALID_FROM <= :EXPORT_DATE and DATE_VALID_TO >= :EXPORT_DATE order by DATE_VALID_FROM asc; Here i uploaded the current Explain-Plan for this query. I'm not a database expert so i don't know which index-type would fit best for this requirement. I have seen that there are many different possible index-types which could be applied. Maybe Oracle Optimizer Hints are helpful, too. Does anyone has a good idea for tuning this sql or can point me in a right direction?

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• Updated resource for java performance tuning

  - by JVA

  Can anyone recommend a web site that includes up to date performance tips for Java? Most of the sites I have found seem to be old and I guess the newer versions (1.5 - 1.7) may have obsoleted some recommendations.

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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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• Looking for application performance tracking software

  - by JavaRocky

  I have multiple java-based applications which produce statistics on how long method calls take. Right now the information is being written into a log file and I analyse performance that way. However with multiple apps and more monitoring requirements this is being becoming a bit overwhelming. I am looking for an application which will collect stats and graph them so I can analyse performance and be aware of performance degradation. I have looked at Solarwinds Application Performance Monitoring, however this polls periodically to gather information. My applications are totally event based and we would like to graph and track this accordingly. I almost started hacking together some scripts to produce Google Charts but surely there are applications which do this already. Suggestions?

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• Hyper-V performance comparisons vs physical client?

  - by rwmnau

  Are there any comparisons between Hyper-V client machines and their physical equivalent? I've looked around and can find 4000 articles about improving Hyper-V performance, but I can't find any that actually do a side-by-side comparison or give benchmarking numbers. Ideally, I'm interested in a comparison of CPU, memory, disk, and graphics performance between something like the following: Some powerful workstation (with plenty of RAM) with Windows 7 installed on it directly Same exact worksation with Hyper-V Server 2008 R2 (the bare Server role) and a full-screen Windows 7 client machine Virtual Server 2005 had performance that didn't compare at all with actual hardware, but with the advances in CPU and hardware-level virtualization, has performance improved significantly? How obvious would it be to a user of the two above scenarios that one of them was virtualized, and does anybody know of actual benchmarking of this type?

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• LTO 2 tape performance in LTO 3 drive

  - by hmallett

  I have a pile of LTO 2 tapes, and both an LTO 2 drive (HP Ultrium 460e), and an autoloader with an LTO 3 drive in (Tandberg T24 autoloader, with a HP drive). Performance of the LTO 2 tapes in the LTO 2 drive is adequate and consistent. HP L&TT tells me that the tapes can be read and written at 64 MB/s, which seems in line with the performance specifications of the drive. When I perform a backup (over the network) using Symantec Backup Exec, I get about 1700 MB/min backup and verify speeds, which is slower, but still adequate. Performance of the LTO 2 tapes in the LTO 3 drive in the autoloader is a different story. HP L&TT tells me that the tapes can be read at 82 MB/s and written at 49 MB/s, which seems unusual at the write speed drop, but not the end of the world. When I perform a backup (over the network) using Symantec Backup Exec though, I get about 331 MB/min backup speed and 205 MB/min verify speeds, which is not only much slower, but also much slower for reads than for writes. Notes: The comparison testing was done on the same server, SCSI card and SCSI cable, with the same backup data set and the same tape each time. The tape and drives are error-free (according to HP L&TT and Backup Exec). The SCSI card is a U160 card, which is not normally recommended for LTO 3, but we're not writing to LTO 3 tapes at LTO 3 speeds, and a U320 SCSI card is not available to me at the moment. As I'm scratching my head to determine the reason for the performance drop, my first question is: While LTO drives can write to the previous generation LTO tapes, does doing so normally incur a performance penalty?

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• Raid-5 Performance per spindle scaling

  - by Bill N.

  So I am stuck in a corner, I have a storage project that is limited to 24 spindles, and requires heavy random Write (the corresponding read side is purely sequential). Needs every bit of space on my Drives, ~13TB total in a n-1 raid-5, and has to go fast, over 2GB/s sort of fast. The obvious answer is to use a Stripe/Concat (Raid-0/1), or better yet a raid-10 in place of the raid-5, but that is disallowed for reasons beyond my control. So I am here asking for help in getting a sub optimal configuration to be as good as it can be. The array built on direct attached SAS-2 10K rpm drives, backed by a ARECA 18xx series controller with 4GB of cache. 64k array stripes and an 4K stripe aligned XFS File system, with 24 Allocation groups (to avoid some of the penalty for being raid 5). The heart of my question is this: In the same setup with 6 spindles/AG's I see a near disk limited performance on the write, ~100MB/s per spindle, at 12 spindles I see that drop to ~80MB/s and at 24 ~60MB/s. I would expect that with a distributed parity and matched AG's, the performance should scale with the # of spindles, or be worse at small spindle counts, but this array is doing the opposite. What am I missing ? Should Raid-5 performance scale with # of spindles ? Many thanks for your answers and any ideas, input, or guidance. --Bill Edit: Improving RAID performance The other relevant thread I was able to find, discusses some of the same issues in the answers, though it still leaves me with out an answer on the performance scaling.

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• How to limit disk performance?

  - by DrakeES

  I am load-testing a web application and studying the impact of some config tweaks (related to disk i/o) on the overall app performance, i.e. the amount of users that can be handled simultaneously. But the problem is that I hit 100% CPU before I can see any effect of the disk-related config settings. I am therefore wondering if there is a way I could deliberately limit the disk performance so that it becomes the bottleneck and the tweaks I am trying to play with actually start impacting performance. Should I just make the hard disk busy with something else? What would serve the best for this purpose? More details (probably irrelevant, but anyway): PHP/Magento/Apache, studying the impact of apc.stat. Setting it to 0 makes APC not checking PHP scripts for modification which should increase performance where disk is the bottleneck. Using JMeter for benchmarking.

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