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• Read only array, deep copy or retrieve copies one by one? (Performance and Memory)

  - by Arthur Wulf White

  In a garbage collection based system, what is the most effective way to handle a read only array if such a structure does not exist natively in the language. Is it better to return a copy of an array or allow other classes to retrieve copies of the objects stored in the array one by one? @JustinSkiles: It is not very broad. It is performance related and can actually be answered specifically for two general cases. You only need very few items: in this situation it's more effective to retrieve copies of the objects one by one. You wish to iterate over 30% or more objects. In this cases it is superior to retrieve all the array at once. This saves on functions calls. Function calls are very expansive when compared to reading directly from an array. A good specific answer could include performance, reading from an array and reading indirectly through a function. It is a simple performance related question.

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• Tuning Red Gate: #1 of Many

  - by Grant Fritchey

  Everyone runs into performance issues at some point. Same thing goes for Red Gate software. Some of our internal systems were running into some serious bottlenecks. It just so happens that we have this nice little SQL Server monitoring tool. What if I were to, oh, I don't know, use the monitoring tool to identify the bottlenecks, figure out the causes and then apply a fix (where possible) and then start the whole thing all over again? Just a crazy thought. OK, I was asked to. This is my first time looking through these servers, so here's how I'd go about using SQL Monitor to get a quick health check, sort of like checking the vitals on a patient. First time opening up our internal SQL Monitor instance and I was greeted with this: Oh my. Maybe I need to get our internal guys to read my blog. Anyway, I know that there are two servers where most of the load is. I'll drill down on the first. I'm selecting the server, not the instance, by clicking on the server name. That opens up the Global Overview page for the server. The information here much more applicable to the "oh my gosh, I have a problem now" type of monitoring. But, looking at this, I am seeing something immediately. There are four(4) drives on the system. The C:\ has an average read time of 16.9ms, more than double the others. Is that a problem? Not sure, but it's something I'll look at. It's write time is higher too. I'll keep drilling down, first, to the unclosed alerts on the server. Now things get interesting. SQL Monitor has a number of different types of alerts, some related to error states, others to service status, and then some related to performance. Guess what I'm seeing a bunch of right here: Long running queries and long job durations. If you check the dates, they're all recent, within the last 24 hours. If they had just been old, uncleared alerts, I wouldn't be that concerned. But with all these, all performance related, and all in the last 24 hours, yeah, I'm concerned. At this point, I could just start responding to the Alerts. If I click on one of the the Long-running query alerts, I'll get all kinds of cool data that can help me determine why the query ran long. But, I'm not in a reactive mode here yet. I'm still gathering data, trying to understand how the server works. I have the information that we're generating a lot of performance alerts, let's sock that away for the moment. Instead, I'm going to back up and look at the Global Overview for the SQL Instance. It shows all the databases on the server and their status. Then it shows a number of basic metrics about the SQL Server instance, again for that "what's happening now" view or things. Then, down at the bottom, there is the Top 10 expensive queries list: This is great stuff. And no, not because I can see the top queries for the last 5 minutes, but because I can adjust that out 3 days. Now I can see where some serious pain is occurring over the last few days. Databases have been blocked out to protect the guilty. That's it for the moment. I have enough knowledge of what's going on in the system that I can start to try to figure out why the system is running slowly. But, I want to look a little more at some historical data, to understand better how this server is behaving. More next time.

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• Performance Tuning Tips for Apache

  Apache is one of the most successful open source projects of our times. A big advantage of this popularity is that over the years people have spent a great deal of time fine tuning the software for better performance. Read on to learn more.

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• Performance Tuning in the Age of Big Data

  Database Administrators must now deal with large volumes of data and new forms of high-speed data analysis. If your responsibility includes performance tuning, here are the areas to focus on that will become more and more important in the age of Big Data. Total DeploymentEnjoy easy release management for your .NET apps, services, and databases with Deployment Manager. Get your free Starter edition now

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• Tuning JVM (GC) for high responsive server application

  - by elgcom

  I am running an application server on Linux 64bit with 8 core CPUs and 6 GB memory. The server must be highly responsive. After some inspection I found that the application running on the server creates rather a huge amount of short-lived objects, and has only about 200~400 MB long-lived objects(as long as there is no memory leak) After reading http://java.sun.com/javase/technologies/hotspot/gc/gc_tuning_6.html I use these JVM options -Xms2g -Xmx2g -XX:MaxPermSize=256m -XX:NewRatio=1 -XX:+UseConcMarkSweepGC Result: the minor GC takes 0.01 ~ 0.02 sec, the major GC takes 1 ~ 3 sec the minor GC happens constantly. How can I further improve or tune the JVM? larger heap size? but will it take more time for GC? larger NewSize and MaxNewSize (for young generation)? other collector? parallel GC? is it a good idea to let major GC take place more often? and how?

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• Performance problems when running Java desktop applications on Citrix Metaframe

  - by demetriusnunes

  We have a desktop Java application running within a Citrix Metaframe server farm and the performance, specially while starting up the app, is very unreliable. Sometimes it takes 15 seconds and sometimes it takes over a minute. It's really unpredicatable. Is there any way to optimize running Java desktop applications within Citrix Metaframe Terminal server sessions to a more reliable performance level? Are there any optimization directed specifically toward Java, such as pre-load JVMs or something like that? Any help would be greatly appreciated.

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• Need help diagnosing network performance issues

  - by tokes

  I am currently working in a developing country as a system analyst for a government department. My area of expertise is software projects, but I've come across a few issues with the network setup in my office. (Unfortunately, being a developing country, there's not a lot of professional help available for this sort of thing.) Most recently, I am trying to diagnose a problem with slowness on the network. Our office is connected to the internet via an ADSL wireless modem/router (called Router). The modem is connected via ethernet to a switch (called Switch). The modem also acts as a wireless access point (called Wireless1), though because it is in a room at the end of the floor, it's range is limited. There are ethernet ports installed around the office. The cables of these all lead back to the same switch. In closer vicinity to the bulk of the client computers, there is another wireless router that acts as an access point for those clients (called Wireless2). That router is connected via ethernet to a wall port, and therefore to Switch. There is also a Windows server which acts as a DNS server (called DNSBox) which is located in the same room and is connected directly to Switch. ---Internet----------| Router/Wireless1 192.168.10.1 ---------------| |----|=========| DNSBox | |-------------------- 192.168.10.4 --------------------| Switch |---Other clients---- | |-------------------- |----|=========| Wireless2 ------------------| 192.168.10.198 One final thing to mention about the network setup. All clients are configured with manual IP addresses. Their router/gateway is set to the IP address of Router, and their DNS server is set to the IP address of DNSBox (with a secondary IP set to an external IP - that of our ISP's DNS server). Here are the symptoms we are experiencing: Clients connected to Wireless2 AP experience slow and unstable connections to the internet. (Slow here is defined as speeds of ~1KB/s, though ping response times seem to be as normal.) Clients connected via ethernet to Switch also experience the same slowness. Clients connected to Wireless1 AP (i.e. connecting via wireless directly to the ADSL modem) experience normal connections to the internet. Clients connected via ethernet to Router (i.e. connecting via ethernet directly to the ADSL modem) also experience normal connections to the internet. I also tried to gauge the connection performance between two machines on the network via ethernet: A file transfer between two clients who were both directly connected to Switch was the fastest; A file transfer between one client directly connected to Switch, and one client directly connected to Router (which is directly connected to Switch) performed much slower; A file transfer between two clients directly connected to Router also performed slowly. Things I have attempted to diagnose the problem: Restarted Switch -- no change. We tried unplugging ethernet jacks from Switch 4 at a time and testing the internet connection. The thought here was that perhaps a client on the network has contracted a virus, and is possibly spamming the network with traffic? (Not very technical, I know.) Unfortunately we couldn't get any significant increases in performance using this method. There were a couple of times when it seemed to be better, but then the connection speed quickly dropped back to slow/dead pace. I didn't want to unplug all jacks from Switch because I was concerned that users might be affected or that I would re-plug in the jacks incorrectly (should I even be worried about that? a port is a port on a switch, right?) I tried swapping the ethernet cable used to connect Router to Switch -- no change in performance. I tried swapping the port used on Switch for Router -- no change in performance. Anyone got any ideas on what this could be? Should I be mentioning specific brand names/models of the hardware used? Virii outbreaks are common in this country/office -- what could I be doing to figure out if a virus is at fault? If it is a virus, it doesn't seem to be generating a lot of traffic to/from the internet, because a) I can still get a good speed if I am directly connected to Router / Wireless1 and b) our ISP data usage has not risen suspiciously. Thanks for your help! Update #1 Here are the specs of some of the hardware: Switch is an Edimax ES3132RL 32-Port 10/100 Rackmount Switch Router is a D-Link DSL-G604T Update #2 I just tried unplugging everything except a laptop and Router from Switch. Speeds are still slow. I guess that means that Router / Switch are not being flooded? It seems more and more likely that the cause is something to do with the interaction between Router and Switch. However, I still can't find any useful resources on setting the LAN speed for either (and I'm not well-versed in these advanced networking configurations).

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• Slow performance by PHP directory operations on virtual machine (Ubuntu libvirt)

  - by thonixx

  Some days ago I installed an Ubuntu server and two running virtual machines with libvirt. Everything works fine except one performance problem. Everytime when I call a PHP script with directory operations the operations are very slow and not performant. Here is an example: http://zother.white-tiger.ch/ And here you see an example without a directory operation and how fast it is: http://michaeltanner.ch/ It's all on the same virtual server. The virtual machine uses 6 cores (8 are available) and 7500 megabytes RAM (8 Gigabyte are available). The disk image format is qcow2. How can I improve the performance?

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• Performance Alert Writing to event Log but not running program

  - by TooFat

  I followed the instructions here How to create and configure performance alerts in Windows Server 2003 to set up an alert if the available logical disk space on one of my drives goes below a certain number. I selected the option to write to the application event log and select the "run this program" option and put in the path to a script that sends me an email. If I copy the path to the script and run it everything works and I get the email. When I start the alert I can see that the limit I set is being exceeded and the logs are being written to the application log, but the email is never being sent. I have the runas user and pword set to a Domain Admin. If I make the "run this program path" to C:\Windows\System32\calc.exe" it also doesn't start up the calculator. The Performance Logs and alerts services is running as Local Admin with allow to interact with desktop. What am I doing wrong?

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• How to troubleshoot performance issues of PHP, MySQL and generic I/O

  - by jbx

  I have a WordPress based website running on a shared hosting. Its response time is very decent (around 2s to retrieve the HTML page and 5s to load all the resources). I was planning to move it to a dedicated virtual server (Ubuntu 12.04 LTS), which should theoretically improve things and make them more consistent given its not shared. However I observed severe performance degredation, with the page taking 10seconds to be generated. I ruled out network issues by editing /etc/hosts on the server and mapping the domain to 127.0.0.1. I used the Apache load tester ab to get the HTML, so JS, CSS and images are all excluded. It still took 10 seconds. I have Zpanel installed on the server which also uses MySQL, and its pages come up quite fast (1.5s) and also phpMyAdmin. Performing some queries on the wordpress database directly through phpMyAdmin returns them quite fast too, with query times in the 10 to 30 millisecond region. Memory is also sufficient, with only 800Mb being used of the 1Gb physical memory available, so it doesn't seem to be a swap issue either. I have also installed APC to try to improve the PHP performance, but it didn't have any effect. What else should I look for? What could be causing this degradation in performance? Could it be some kind of I/O issue since I am running on a cloud based virtual server? I wish to be able to raise the issue with my provider but without showing actual data from some diagnosis I am afraid he will just blame my application. UPDATE with sar output (every second) when I did an HTTP request: 02:31:29 CPU %user %nice %system %iowait %steal %idle 02:31:30 all 0.00 0.00 0.00 0.00 0.00 100.00 02:31:31 all 2.22 0.00 2.22 0.00 0.00 95.56 02:31:32 all 41.67 0.00 6.25 0.00 2.08 50.00 02:31:33 all 86.36 0.00 13.64 0.00 0.00 0.00 02:31:34 all 75.00 0.00 25.00 0.00 0.00 0.00 02:31:35 all 93.18 0.00 6.82 0.00 0.00 0.00 02:31:36 all 90.70 0.00 9.30 0.00 0.00 0.00 02:31:37 all 71.05 0.00 0.00 0.00 0.00 28.95 02:31:38 all 14.89 0.00 10.64 0.00 2.13 72.34 02:31:39 all 2.56 0.00 0.00 0.00 0.00 97.44 02:31:40 all 0.00 0.00 0.00 0.00 0.00 100.00 02:31:41 all 0.00 0.00 0.00 0.00 0.00 100.00 My suspicion that this comes from I/O related issue is also because a caching plugin I use to reduce the amount of queries to the database, by precompiling PHP pages is actually making things worse instead of better. It seems that file access is making things worse instead.

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• VMWare Workstation Performance

  - by tekiegreg

  Hi there, awhile ago I upgraded my laptop to Windows 7 x64 from Windows XP 32 bit edition. However not before virtualizing the physical installation and I continue to run it under VMWare Workstation today. The performance on the resulting VM is just absolutely atrocious! I've done a lot of uninstalling stuff that's not longer needed since the machine is virtual in an effort to reduce RAM, but in general the responsiveness seems sluggish. I also run the Virtual Machine on it's own separate HD that is seldom used by the host OS. I'm just hoping for some general tips in increasing VMWare performance anywhere, thoughts? EDIT: Both of the below answers were excellent starting points for me. However I did like the selected answer's strategies on disk management. I am running the Virtual Machine in a separate external hard disk, likely I'm going to have to reconfigure somehow. Thanks all!

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• Optimizing PHP<>MySQL performance

  - by BarsMonster

  I am trying to optimize my PHP<MySQL on this test script: <? for($i=0;$i<100;$i++)//Itterations count $res.= var_dump(loadRow("select body_ru from articles where id>$i*50 limit 100")); print_r($res); ?> I have APC, and article table have an index on id. Also, all these queries are hitting query cache, so sole MySQL performance if great. But when I am using ab -c 10 -t 10 to bench this scipt, I am getting: 100 itterations: ~100req/sec (~10'000 MySQL queries per second) 5 itteration: ~200req/sec 1 itteration: ~380req/sec 0 itteration: ~580req/sec I've tried to disable persistent connections in PHP - it made it slower a bit. So, how can I make it work faster, provided that MySQL is not limiting performance here?

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• Tips to increase performance of a Windows computer

  - by Niyaz

  What are some general guidelines to increase the speed/performance of my Windows machine?

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• Performance affects of compressing Program Files on Windows / NTFS

  - by SRobertJames

  What are the performance affects of compressing Program Files on Windows NTFS? On a fast, multicore machine, the overhead of decompression is minimal. Machines are generally disk bound, and if you can reduce the disk load by compression, you often speed things up. (Microsoft says that the built in compression of Windows Search indexes actually improves speed for this reason.) On the other hand, Windows' virtual memory is complicated. Perhaps if files are compressed, they can't be paged out simply. And there may be other issues. In short: On a fast, multicore machine with a relatively slow disk, what performance affects will compressing Program Files have?

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• Good book for building high performance web sites?

  - by Arne Evertsson

  Any recommendations for a book about building and running high performance, high-availability web sites on Linux?

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• Verify server performance

  - by George Kesler

  I'm looking for a quick and SIMPLE way to verify that new servers are performing as expected. The most important metric is disk performance, second is network performance. I’m trying to prevent problems caused by misconfiguration of RAID arrays, NIC teaming etc. The solution should work with both physical and virtual servers. I don’t need sophisticated analysis with different workloads, just one set of benchmarks which I would run against a reference server and later compare to new ones. One problem is that most benchmarks are not giving accurate results when running on a VM.

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• General video performance affected on Mac OSX 10.5 (PowerBook G4)

  - by r0ca

  Hi all, I'm quite new to Mac and I just got a PowerBook G4 for free. I installed OSX 10.5 on it and for the first two weeks, everything was going kinda smooth even if this is similar to a P3. I'm not expecting awsome video performance but at least be able to watch some videos from Youtube. Yesterday night, I installed Office 2008 for mac and this morning, even after a reboot, my computer is way much slower that I used to know. I watched a youtube video and the framerate was 1:1. I also noticed it on flash adds, it's way slower! Is there anything that I can do to increase video performance, see what's the process list running and taking more GPU or CPU, what's taking more ram and stuff like that?! What do you guys, Mac pros, would do on an old laptop with OSX 10.5 Thanks!

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• Skyrim: Heavy Performance Issues after a couple of location changes

  - by Derija

  Okay, I've tried different solutions: ENB Series, removing certain mods, checking my FPS Rate, monitoring my resources, .ini tweaks. It's all just fine, I don't see what I'm missing. A couple of days ago, I bought Skyrim. Before I bought the game, I admit I had a pirated copy because my girlfriend actually wanted to buy me the game as a present, then said she didn't have enough money. Sick of waiting, I decided to buy the game by myself. The ridiculous part is, it worked better cracked than it does now uncracked. As the title suggests, after entering and leaving houses a couple of times, my performance obviously drops extremely. My build is just fine, Intel i5 quad core processor, NVIDIA GTX 560 Ti from Gigabyte, actually stock-OC, but manually downclocked to usual settings using appropriate Gigabyte software. This fixed the CTD issues I had before with both Skyrim and BF3. I have 4GB RAM. A website about Game Tweaks suggested that my HDD may be too slow. A screenshot of a Windows Performance Index sample with the subscription "This is likely to cause issues" showed the HDD with a performance index of 5.9, the exact same mine has, so I was playing with the thought to purchase an SSD instead, load games onto it that really need it like Skyrim, and hope it'd do the trick. Unfortunately, SSDs are likewise expensive, compared to "normal" HDDs... I'm really getting desperate about it. My save is gone because the patches made it impossible to load saves of the unpatched version and I already saved more than 80 times despite being only level 8, just because every time I interact with a door leading me to another location I'm scared the game will drop again. I can't even play for 30 mins straight anymore, it's just no fun at all. I've researched for a couple of days before I decided to post my question here. Any help is appreciated, I don't want to regret having bought the game... Since it actually is the best game I've played possibly for ever. Sincerely. P.S.: I don't think it's necessary to say, but still, of course I'm playing on PC. P.P.S.: After monitoring both my PC resources including CPU usage and HDD usage as well as the GPU usage, I don't see any changes even after the said event. P.P.P.S.: Original question posted here where I've been advised to ask here.

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• RAID10 without write-back cache = horrible write performance?

  - by Harry Mexican

  I have just provisioned a dedicated server on singlehop. I'm running it through some tests to know what to expect performance-wise. On the I/O side (with 4 1TB disks in RAID 10) I get: write-cache disabled 200 MB/s read throughput 30 MB/s write throughput I thought that was really low compared to my desktop HD which gets 150-150 or so. So I had a chat with them and they suggested enabling the write cache. New results: write-cache enabled 280 MB/s read 260 MB/s write which is great and all but means I'd have to add a BBU for an additional monthly cost. Is it normal for the write throughput to be 1/4 of a regular drive on RAID10, if you don't have write cache? It almost feels like its intentionally bad to force you to pony up for the BBU. I'd be happy with normal non-raid performance of 150/150.

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• Analyzing Linux NFS server performance

  - by Kamil Kisiel

  I'd like to do some analysis of our NFS server to help track down potential bottlenecks in our applications. The server is running SUSE Enterprise Linux 10. The kind of things I'm looking to know are: Which files are being accessed by which clients Read/write throughput on a per-client basis Overhead imposed by other RPC calls Time spent waiting on other NFS requests, or disk I/O, to service a client I already know about the statistics available in /proc/net/rpc/nfsd and in fact I wrote a blog post describing them in depth. What I'm looking for is a way to dig deeper and help understand what factors are contributing to the performance seen by a particular client. I want to analyze the role the NFS server plays in the performance of an application on our cluster so that I can think of ways to best optimize it.

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• Determining Performance Limits

  - by JeffV

  I have a number of windows processes that pass messages between them hat a high rate using tcp to local host. Aside from testing on actual hardware how can I assess what my hardware limit will be. These applications are not doing CPU intensive work, mostly decomposing and combining messages, scanning over them for special flag in the data etc.. The message size is typically 3k and the rate is typically ~10k messages per second. ~30MB per second between processing stages. There may be 10 or more stages depending. For this type of application, what should I look to for assessing performance? What do I look for in a server performance wise? I am currently running an XEON L5408 with 32 GB ram. But I am assuming cache is more important than actual ram size as I am barely touching the ram.

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• performance block countries using iptables /netfilter

  - by markus

  It's easy to block IPs from country using iptables (e.g. like http://www.cyberciti.biz/faq/block-entier-country-using-iptables/). However I read that the performance can go down if the deny list get too large. An alternative is installing the iptables geoip patch or using ipset ( http://www.jsimmons.co.uk/2010/06/08/using-ipset-with-iptables-in-ubuntu-lts-1004-to-block-large-ip-ranges/) instead of iptables. Does anyone have experience with the various approaches and can say something about the performance differences ? Are there are other ways to block country IPs in linux which I did't mentioned above?

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• Does shutdown idle VMs improve the performance?

  - by Samselvaprabu

  Often our team members are coming to me with a compliant that their VMs are slow. Our team members suggested to shutdown some of the VMs temporarily and try to access the VM. But most cases that would not help. Assume that i have assigned 4 GB for and 2 CPUs for my VM. So ideally it should not face performance issue. As our ESXi 4.1 server has multiple VM in the same server (we have overcommited memory and CPU). Does shut down other VM really helps to improve performance or not? [Note : We are using ESXi 4.1 and our hardware is R710 server. We have more number of VMs in single server so we have overcommited memory.]

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• Exchange 2010 SP2 OWA performance

  - by Frederik Nielsen

  How do I increase performance in OWA 2010 SP2? I am running CAS on a seperate installation, which has 8GB RAM and 4 CPU cores - running virtualized in a vmware environment. However, the load times are pretty bad, so is there any way to improve those? I am thinking of installing a linux cache-stuff-server in front of the OWA, but will that work? And how should it be done? Allright, I "fixed" it - was just something temporary issue. Thanks for your replies

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• Strange performance from RAID5 using WD RE4 disks

  - by Howard

  I've noticed a bit of a performance issue with some WD RE4 drives I'm using under AMD's hardware RAID solution. First a bit of background: Environment: Windows 7 home premium x64 HDD's: 3x 1TB WD Raid Edition 4 in a RAID 5 setup with 128 kbyte stripe (2TB usable space) Testing Tool: HD Tune, process set to "High Priority" Processor: AMD Phenom II x6 1100T Ram: 16GB DDR3/1600mhz Motherboard: MSI 970A-G45 The image below pretty much depicts the issue I'm having. Every test has the same thing, a period of similar length where the performance drops to a few megabytes a second. This can't be a TLER issue as the purpose of RE4's is to work around that. Any help would be greatly appreciated.

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