Performance tuning is the process of modifying a system to improve its efficiency. This is also known as optimizing.

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FreeBSD performance tuning. Sysctls, loader.conf, kernel

I wanted to share knowledge of tuning FreeBSD via sysctl.conf / loader.conf / KENCONF / etc. It was initially based on Igor Sysoev's (author of nginx) presentation about FreeBSD tuning up to ...
22
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3answers
9k views

Linux - real-world hardware RAID controller tuning (scsi and cciss)

Most of the Linux systems I manage feature hardware RAID controllers (mostly HP Smart Array). They're all running RHEL or CentOS. I'm looking for real-world tunables to help optimize performance for ...
21
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7answers
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Is it OK to run perfmon on production servers? And why?

Or should perfmon be limited to a Dev/QA server with load tests that simulate production activity? I'd like to run perfmon for two days (like Sql Server master Brent Ozar suggests) to get an overall ...
14
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7answers
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yslow says etags are misconfigured. how to configure etags properly on IIS7?

running ySlow on a website I support, I noticed it reported that the etags are misconfigured for the site images (e.g. *.jpg, *.png, *.gif). Can anyone help explain what I have to do to get IIS7 ...
13
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3answers
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Building a 1,000M row MySQL table

This question is reposted from Stack Overflow based on a suggestion in the comments, apologies for the duplication. Questions Question 1: as the size of the database table gets larger how can I tune ...
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7answers
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Apache Tomcat chokes after 300 connections

We have an apache webserver in front of Tomcat hosted on EC2, instance type is extra large with 34GB memory. Our application deals with lot of external webservices and we have a very lousy external ...
10
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2answers
7k views

Should we mount with data=writeback and barrier=0 on ext3?

We've been running a server on a VM at a hosting company, and have just signed up for a dedicated host (AMD Opteron 3250, 4 cores, 8GB RAM, 2 x 1TB in software RAID, ext3). While running performance ...
10
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2answers
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Tuning (and understanding) table_cache in mySQL

I ran the excellent MySQL performance tuning script and started to work through the suggestions. One I ran into was TABLE CACHE Current table_cache value = 4096 tables You have a total of 1073 ...
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13answers
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Postfix performance

Running postfix on ubuntu, sending alot of mail ( ~ 1 million messages ) per day. loads are extremly high but not much in terms of cpu and memory load. Anyone in a similiar situation and know how to ...
8
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5answers
11k views

Performance Tuning a High-Load Apache Server

I am looking to understand some server performance problems I am seeing with a (for us) heavily loaded web server. The environment is as follows: Debian Lenny (all stable packages + patched to ...
8
votes
2answers
785 views

Linux RAID-0 performance doesn't scale up over 1 GB/s

I have trouble getting the max throughput out of my setup. The hardware is as follow : dual Quad-Core AMD Opteron(tm) Processor 2376 16 GB DDR2 ECC RAM dual Adaptec 52245 RAID controllers 48 1 TB ...
7
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3answers
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What are your tricks for optimizing your Subversion configuration?

For a Linux or Windows system, what tricks do you do to optimize your Subversion server? The following are my current tricks for a Linux system serving over Apache with HTTPS and backed by Active ...
7
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2answers
3k views

CPU0 is swamped with eth1 interrupts

I've got an Ubuntu VM, running inside Ubuntu-based Xen XCP. It hosts a custom FCGI-based HTTP service, behind nginx. Under load from ab the first CPU core is saturated, and the rest is under-loaded. ...
7
votes
1answer
5k views

Interpreting ethtool Coalesce output

Other than tx and rx being the transmit and recieve, can anyone explain what the fields mean in ethtool -c's (Coalescing output) and what effect they have on how coalescing works? Coalesce parameters ...
7
votes
1answer
1k views

Why change net.inet.tcp.tcbhashsize in FreeBSD?

In virtually every FreeBSD network tuning document I can find: # /boot/loader.conf net.inet.tcp.tcbhashsize=4096 This is usually paired with some unhelpful statement like "TCP control-block hash ...
7
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2answers
1k views

What are the implications of the SHOWPLAN permission on SQL Server 2005?

A user wants the SHOWPLAN permission in order to use Execution Plans to tune a query. What are the implications of this permission. Is it safe to grant a user? I've seen the security note here, and ...
7
votes
3answers
468 views

Unexplained periodic humps in system CPU usage on W2K3E

We have a Windows 2003 R2 Enterprise 64-bit server running a custom workload suffering from an odd performance problem. The pared-down version below suffers from a smaller hump, but it's qualitatively ...
7
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3answers
3k views

NetBackup Multiplexing for Oracle RMAN Backups

My question is... what multiplexing factor in NetBackup is recommended / do you use for Oracle RMAN backups over 1Gb/s management network to LTO3? JB Background: With enterprise backup tools like ...
6
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4answers
4k views

Configuring NTFS file system for performance

We have an application that is planning to store around 1.1TB of XML files which average 8.5kb in size. These represent a rolling 18 months of data, with around 200,000 new files being created every ...
6
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1answer
134 views

How to prevent IO Load under Linux for Video serving?

I'm currently serving videos of conferences via Nginx on 3 servers; 4 cores, enough memory (no swap used) and RAID-10 with 8 drives per server. Unfortunately iostat -xd 1 gives me 100% on all 3 ...
6
votes
2answers
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what does locked % in mongostat mean?

When running mongostat to look at our mongo database, I'll frequently see the locked % number jump up, sometimes as high as 80%. Here's a few example rows: insert query update delete getmore ...
6
votes
4answers
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Windows 7 network performance tuning for LAN

I want to tune Windows 7 TCP stack for speed in a LAN environment. Bit of background info: I've got a Citrix XenServer set up with Windows 2008R2, Windows 7 and Debian Lenny with Citrix kernel, ...
6
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1answer
1k views

What are some TCP tuning tips for a service hit by iPhone clients on mobile networks like 3G?

I am a developer that has the good+bad situation of designing a network service that will be hit very hard by iPhone clients. The iPhone app has over 10MM downloads in the past year and now I'm ...
6
votes
2answers
5k views

Best sysctl.conf configuration for high load - extremely busy content streaming server

What is the best sysctl.conf configuration for a high load, extremely busy content streaming server ? The server fetches the content from remote servers like amazon, s3, etc. then uses php to ...
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8answers
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Hard Drive Speed: RPM vs. Cache

When trying to choose a SATA magnetic hard drive (not SSD) for high performance for both random and linear access, which should be the primary factor? For example: would a 10k RPM drive with 16MB ...
5
votes
4answers
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Find out which task is generating a lot of context switches on linux

According to vmstat, my Linux server (2xCore2 Duo 2.5 GHz) is constantly doing around 20k context switches per second. # vmstat 3 procs -----------memory---------- ---swap-- -----io---- -system-- ...
5
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2answers
4k views

Faster IMAP searching for Courier IMAP server on Linux

I am looking for tips on improving IMAP search performance using Courier IMAP. The current version is 4.2.1. Unlike in the question "Fast search for IMAP?", I'm specifically looking for server side ...
5
votes
2answers
134 views

ZFS Equivalent of lvdisplay snap_percent

I've been using LVM snapshots for backing up MySQL databases. FLUSH TABLES WITH READ LOCK is issued and then lvcreate --snapshot --size 4G etc. Because the database is live while the snapshot is ...
5
votes
1answer
882 views

How do I test the effect of ionice (against a device using the cfq scheduler)?

I'm trying to construct an experiment to measure the effect of ionice. What I'd like to do is to (per another answer on serverfault) cause frequent enough I/O that a sufficiently "niced" process is ...
4
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7answers
3k views

Linux tool/command to check file system performance

What is the simplest way to check read/write performance to a specific location (e.g. a mounted iSCSI device). I suspect I can't use hdparm because that's lower level. Am I right?
4
votes
3answers
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Understanding RedHat's recommended tuned profiles

We are going to roll out tuned (and numad) on ~1000 servers, the majority of them being VMware servers either on NetApp or 3Par storage. According to RedHats documentation we should choose the ...
4
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1answer
501 views

Ubuntu HTTP latency falling into strange quantiles

I have an Ubuntu 10.10 server with plenty of RAM, bandwidth and CPU. I'm seeing a strange, repeatable pattern in the distribution of latencies when serving static files from both Apache and nginx. ...
4
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1answer
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PostgreSQL - count() performance and how to tweak it?

I've done some reading in google and the only thing I did was get myself confused. Some of the people say that count() is slower with many records, others say you can cache the number or even use ...
4
votes
1answer
381 views

How does php know what memcached node to look for its data in?

I am new to the world of Memcached clusters If I have a php web application that is using memcache - how does it does its hash and decide what node to check for a particular value to avoid having to ...
4
votes
2answers
625 views

ratelimit POST requests

Im running a large wordpress multiuser site. I have a varnish cache infront of the wordpress application server. As it make no sense to cache POST requests, i am vulnerable to DOS using lots of POST´s ...
4
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1answer
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What is the best TCP congest algorithm to use for a mobile device?

Given the multitude of TCP algorithms available now and the rise of Linux based mobile devices, what are ideal algorithm(s) to consider? From reading of the various implementations, Veno and ...
3
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3answers
703 views

Disk write speed much slower than read speed

I have a VPS server (WiredTree), running CentOS. After experiencing some performance issues I created a simple benchmark for disk read/write speed using the following script: echo Write to disk dd ...
3
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4answers
1k views

Optimizing RAID 5 for BackupPC use (small random reads)

I am running a BackupPC server with a hardware RAID 5 for the main storage of the backups. Since the machine was created on a tiny budget, the controller is a 3Ware 9500S-4LP for the PCI port and the ...
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6answers
1k views

MySQL performance tuning

I'm looking for a succinct list of common pitfalls and optimizations for tuning a MySQL server as used for mid-size websites. In general, the type of advice I'm looking for here is information that ...
3
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3answers
3k views

HP P410 RAID + Samsung 830 SSDs + Debian 6.0 - What performance to expect?

I'm renting two dedicated servers from a hosting company. Here are the specs: server1: HP ProLiant DL165 G7 2x AMD Opteron 6164 HE 12-Core 40 GB RAM HP Smart Array P410 RAID controller 2x Samsung 830 ...
3
votes
2answers
2k views

How can I tell which page is creating a high-CPU-load httpd process?

I have a LAMP server (CentOS-based MediaTemple (DV) Extreme with 2GB RAM) running a customized Wordpress+bbPress combination . At about 30k pageviews per day the server is starting to groan. It ...
3
votes
3answers
262 views

How to profile for HDD usage pattern?

I'm considering upgrading the storage system for some of my servers, and all the guides and manuals advise to consider the storage usage patterns of your app before deciding on a (RAID? SSD? iSCSI? ...
3
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3answers
2k views

Database I/O acceleration using solid state drives

What is the experience improving database performance using solid-state drives (particularly for PostgreSQL databases) such as HP's IO Accelerator? Did you see any marked improvements?
3
votes
1answer
3k views

Openfiler iSCSI performance

Hoping someone can point me in the right direction with some iSCSI performance issues I'm having. I'm running Openfiler 2.99 on an older ProLiant DL360 G5. Dual Xeon processor, 6GB ECC RAM, Intel ...
3
votes
2answers
149 views

Measuring I/O Performance Paradox

I'm trying to figure out the correct way to get the 'real world' write performance of my NFS cluster. The NFS export is mount on a XEN hypervisor, and I'm running 'dd' from within a VM. What I ...
3
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4answers
957 views

How can I make this setup faster?

Hey StackOverlow Community, I currently am using some software that stores a bunch of XML files. All the files are under 25k bytes. The makers of the software state the performance is based on ...
3
votes
3answers
558 views

It is possible move a specific file to the beginning of the disk?

It is possible move a specific file to the beginning of the disk? I want to move my virtual machine disk files (virtual disk) to the beginning of the disk to improve disk access performance. I believe ...
3
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1answer
3k views

Disabling CPU management

If I add the following processor.max_cstate=0 to the kernel command line for boot up, does that disable all CPU power management and throttling? I also found: ...
3
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1answer
323 views

How long is the “defined grace period” for the idle scheduling class of the CFQ io scheduler?

The ionice man page says A program running with idle io priority will only get disk time when no other program has asked for disk io for a defined grace period. Where is this "grace period" ...
3
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3answers
1k views

Linux's best filesystem to work with 10000's of files without overloading the system I/O

It is known that certain AMD64 Linuxes are subject of being unresponsive under heavy disk I/O (see Gentoo forums: AMD64 system slow/unresponsive during disk access (Part 2)), unfortunately have such ...