Questions about server hardware and software performance, or network performance.
80
votes
4answers
88k views
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 ...
71
votes
4answers
11k views
Why is TCP accept() performance so bad under Xen?
The rate at which my server can accept() new incoming TCP connections is really bad under Xen. The same test on bare metal hardware shows 3-5x speed ups.
How come this is so bad under Xen?
Can you ...
49
votes
13answers
7k views
Are networks now faster than disks?
This is a software design question
I used to work on the following rule for speed
cache memory > memory > disk > network
With each step being 5-10 times the previous step (e.g. cache ...
47
votes
8answers
3k views
How can a single disk in a hardware SATA RAID-10 array bring the entire array to a screeching halt?
Prelude:
I'm a code-monkey that's increasingly taken on SysAdmin duties for my small company. My code is our product, and increasingly we provide the same app as SaaS.
About 18 months ago I moved ...
40
votes
9answers
71k views
What limits the maximum number of connections on a Linux server?
What kernel parameter or other settings control the maximum number of TCP sockets that can be open on a Linux server? What are the tradeoffs of allowing more connections?
I noticed while load testing ...
33
votes
23answers
43k views
How to copy a large number of files quickly between two servers
I need to transfer a huge amount of mp3s between two serves (Ubuntu).
By huge I mean about a million files which are on average 300K.
I tried with scp but it would have taken about a week. (about 500 ...
32
votes
5answers
1k views
Pay no attention to that SAN behind the curtain
Once upon a time, I built my own SQL servers, and had control over drive configuration, RAID levels, etc. The traditional advice of separation of data, logs, tempdb, backups, (depending on budget!) ...
30
votes
7answers
11k views
How much of a performance hit for https vs http for apache?
Roughly how much of a performance hit will https take compared to http for the same page? Suppose I can handle 1000 requests/s for abc.php, how much will it decrease by when accessed through https? I ...
30
votes
7answers
57k views
Xen vs KVM in performance
What is faster on same hardware - Xen or KVM?
I'm trying to pick-up a virtualization technology to work, which gives the best performance.
There are some benchmarks here that I found on the subject:
...
25
votes
9answers
4k views
To improve SQL performance, why not just put lots of RAM rather than having faster hard disks?
People keep telling me that in order to improve an SQL server's performance, buy the fastest hard disks possible with RAID 5, etc.
So I was thinking, instead of spending all the money for ...
22
votes
10answers
13k views
Is virtual machine slower than the underlying physical machine?
This question is quite general, but most specifically I'm interested in knowing if virtual machine running Ubuntu Enterprise Cloud will be any slower than the same physical machine without any ...
22
votes
7answers
9k views
What are the performance differences between Raid 0,1,5,6,10
I have heard/read different performance stories on the various raid flavors. I am curious what the agreed upon best answer is.
21
votes
4answers
11k views
Which PHP (opcode) cache one should use and why?
I keep hearing about some PHP (opcode) caches like - APC, XCache, Memcache, eAccelerator, etc.
But I couldn't ever figure out how to go about choosing one. Apart from performance benefit, which a ...
19
votes
4answers
935 views
Why would a heavily disk intensive application run faster on a SAN than on a Physical Disk?
Why would a heavily disk intensive application run faster on a SAN than on a Physical Disk? I would have expected the Physical disk to be slightly faster but in fact the process ran 100 times faster ...
19
votes
3answers
5k views
PHP: What are the advantages of FastCGI over mod_php?
It was recently suggested to me that I use FastCGI with PHP. Now I went to the FastCGI page and read it but I don't really understand what the advantages are.
18
votes
5answers
1k views
Extremely fast booting server
I'm changing the way that our DHCP/DNS stuff works at work. Currently we've got 3 DNS servers, and a DHCP box. All of them are VMs.
There's a circular dependency where stuff booting requires NFS, ...
18
votes
10answers
14k views
How to make `rm` faster on ext3/linux?
I have ext3 filesystem mounted with default options. On it I have some ~ 100GB files.
Removal of any of such files takes long time (8 minutes) and causes a lot of io traffic, which increases load on ...
18
votes
7answers
5k views
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 ...
18
votes
8answers
13k views
What impact does full hard drive encryption have on performance?
We have HP notebooks here at work, and it is policy to have HP's hard drive encryption turned on to protect client databases and IP in the case of loss/theft.
I was wondering if there was any ...
18
votes
8answers
6k views
Analyzing Linux NFS server performance
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 ...
17
votes
2answers
868 views
Can a virtualized machine have the CPU and RAM resources of multiple underlying physical machines?
We are studying implementing some virtualized servers here, but we don't know what will be better suitable for us. Some folks are saying better have two huge servers, and others are saying have like a ...
16
votes
3answers
31k views
Optimal values for ServerLimit, MaxClients, MaxRequestsPerChild directives
I'm running a traffic intense site plenty of dynamic content, mostly user-generated.
The server is a dedicated one and has a total of 4 Intel(R) Xeon(R) CPU X3210 @ 2.13GHz proccesors. I need to know ...
15
votes
5answers
13k views
Can a pool of memcache daemons be used to share sessions more efficiently?
We are moving from a 1 webserver setup to a two webserver setup and I need to start sharing PHP sessions between the two load balanced machines. We already have memcached installed (and started) and ...
15
votes
7answers
17k views
How can you know what is w3wp.exe doing? (or how to diagnose a performance problem)
I'm having a performance problem in a site we've made, and I'm not exactly sure how to start diagnosing it.
The short description is: We have a very small site (http://hearablog.com) with very little ...
15
votes
4answers
989 views
HTTP Compression on IIS 6.0 (Windows Server 2003)
There are many things you have to do/consider when you want to enable HTTP compression on IIS 6.0 (Windows Server 2003).
Can somebody please provide a comprehensive list of the actions you have to ...
14
votes
8answers
13k views
How do I profile MySQL?
What tools exist to profile MySQL, like how MSSQL 2000+ does with the SQL Profiler?
I'd want to trace things like SQL statements executed, execution times, execution plan, etc.
14
votes
16answers
9k views
Real time monitoring of MS Windows servers and their services
We have a bunch of large HDTVs in our monitoring office keeping an eye on all of our production equipment.
We are monitoring:
Cisco routers
HP switches
HP proliant servers
Windows 2003
IIS
SQL ...
14
votes
6answers
474 views
First days online : how not to kill your site
Suppose you have this fancy new site, with lots of data (like big images), and you're about to put it online. If you do "too much" publicity, during the first days, the site will be overwhelmed with ...
14
votes
5answers
21k views
How many Context Switches is “normal” (as a function of CPU cores (or other))?
Do any of you have a rule of thumb as to how many context switches (per processor core) is Normal on a Linux server?
My college here brought it up, and he's seeing 16K on a 8-core x86_64 machine.
...
14
votes
3answers
10k views
GlusterFS vs Ceph, which is better for production use for the moment?
I am evaluating GlusterFS and Ceph, seems Gluster is FUSE based which means it may be not as fast as Ceph. But looks like Gluster got a very friendly control panel and is ease to use.
Ceph was ...
13
votes
10answers
2k views
Would rebooting the server in a schedule be good idea for performance?
I am wondering if rebooting a server in a schedule would be good idea for performance.
Let's say we want to reboot the server at 02:00 AM per 2 nights.
The server here is Windows Server 2008 R2. ...
13
votes
17answers
10k views
What network file sharing protocol has the best performance and reliability?
We have a setup with a few web servers being load-balanced. We want to have some sort of network shared storage that all of the web servers can access. It will be used as a place to store files ...
13
votes
10answers
5k views
System degredation - does Windows slow down over time?
I am having a small squabble at work with our admin regarding a colleague's laptop. The laptop is bordering on unusable. The admin tidied up some temp directories and defragged the HDD a few months ...
13
votes
4answers
11k views
How to pick between RabbitMQ and ZeroMQ or something else?
I'm looking for a queuing system which is fast and reliable and potentially can be spread across machines. Platform is Linux. Open source is preferable.
Both RabbitMQ and ZeroMQ look good but I ...
13
votes
7answers
8k views
What is the best filesystem for insert performance on PostgreSQL?
I'm curious if anyone out there has done any experimentation or comparisons between file systems and database performance. On Linux, I'm wondering what is the optimal file system for a postgres ...
13
votes
3answers
2k views
Some Linux systems become very slow when Redis is loading a big dataset
I received a report from a Redis user, and I'm not sure what to reply as I'm not an expert in the area of Linux and its scheduler, however we (as the Redis project) need to figure this kind of issues ...
13
votes
4answers
3k views
Apache or NGINX for PHP?
I've read quite a bit on the major benefits to running NGINX over Apache for serving static files. However, I have never seen an article talking about Apache vs NGINX for serving PHP pages.
Question: ...
13
votes
3answers
395 views
Does this prove a network bandwidth bottleneck?
I've incorrectly assumed that my internal AB testing means my server can handle 1k concurrency @3k hits per second.
My theory at at the moment is that the network is the bottleneck. The server can't ...
13
votes
2answers
8k views
limit linux background flush (dirty pages)
Background flushing in linux happens when either too much written data is pending (adjustable via /proc/sys/vm/dirty_background_ratio) or a timeout for pending writes is reached ...
12
votes
5answers
835 views
Which bots and spiders should I block in robots.txt?
In order to:
Increase security of my website
Reduce bandwidth requirements
Prevent email address harvesting
12
votes
3answers
2k views
How fast is MySQL replication?
I'm considering setting up replication of our mysql db to be able to have local slaves in each of our branch offices, while having the master in the main office to improve application performance ...
12
votes
4answers
447 views
How to best tune a Windows development machine?
How to best tune a Windows PC for development purposes?
12
votes
3answers
1k views
MySQL Replication Performance
I'm having a serious issue with MySQL 5.5 replication performance between two machines, mostly myISAM tables with statement based replication. The binary logs and mysql data directory are both located ...
12
votes
1answer
453 views
Apache performance degrades dramatically above ~256 simultaneous requests
I'm running a relatively low-traffic site that experiences a large spike in visitors once a week following a site update. During this spike, site performance is extremely poor compared to the rest of ...
12
votes
4answers
418 views
IIS7 ASP.NET application - 2 identical apps in 2 identical app pools, 1 is responsive and 1 is not
I have an ASP.NET (v4.0) web app that is installed in a virtual directory (as an application) and is hosted in it's own app pool.
This is repeated for each instance of the app (i.e. per customer).
...
11
votes
11answers
6k views
Should I run my database off of a RAID 5 configuration?
I've heard that the write performance of RAID 5 can be appalling at times. While I want the redundancy that it provides I don't want to sacrifice my database insert/update times.
Is this something I ...
11
votes
13answers
5k views
Why would wireless routers become less reliable over time?
I've been curious about this for awhile now. I don't know if I'm seeing a real pattern or not, but having worked with many home office/small office wireless routers for a few years now, I've noticed ...
11
votes
11answers
10k views
What can cause slow ssh session? [closed]
I ssh on remote host but terminal performance is poor. Symbols I am typing are not shown immediately, but with some delay. Sometimes two symbols are shown at one time after delay.
11
votes
2answers
367 views
Performance impact of running different filesystems on a single Linux server
The book "HBase: The definitive guide" states that
Installing different filesystems on a single server is not recommended.
This can have adverse effects on performance as the kernel may have to
...
11
votes
1answer
8k views
Determining which process is causing heavy disk I/O?
I've seen this question:
How to identify heavy write to disk?
And I've used dstat and atop before...but they don't seem to pinpoint what process is causing disk I/O. For example, from dstat:
dstat ...
