Questions about server hardware and software performance, or network performance.

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14
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5answers
1k 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
14
votes
6answers
504 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
16answers
11k 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
1answer
195 views

Vendor whitepaper says: 5Mpps no prob. I'm already hitting a wall at 120kpps. Where's the bottleneck?

HP's whitepaper on their QLogic (fka Broadcom) NetXtreme II adapters, which includes the specific NIC that I'm testing, states (page 7) that their small packet performance for packets up to 256 ...
14
votes
3answers
783 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 ...
14
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 ...
14
votes
3answers
13k views

GlusterFS vs Ceph, which is better for production use for the moment? [closed]

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 ...
14
votes
2answers
289 views

NFS poor write performance

I have two machines connected with 10Gbit Ethernet. Let one of them be NFS server and another will be NFs client. Testing network speed over TCP with iperf shows ~9.8 Gbit/s throughput in both ...
13
votes
14answers
11k 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 ...
13
votes
11answers
16k views

How to monitor and log the memory/cpu usage of processes over time? [closed]

I am looking for a way to diagnose issues, such as swap death, where a balooning memory process fills up swap and kills the whole machine (such as apache). I'm already using cacti and I can set up ...
13
votes
2answers
18k views

Best Mysql cache settings for 8gb RAM dedicated mysql server using only Innodb (5gb database)

I'm a pretty big noob when it comes to setting up mysql for performance. And honestly I'm not worried about the fine tuning to squeeze every last bit of performance out of mysql, but I do know that ...
13
votes
1answer
5k views

Apache 2.2 mpm_worker: more threads or more processes?

When using the Worker MPM in Apache, you can fiddle with the number of child processes and the number of server threads per child process. What are the advantages and disadvantages of each? Under ...
13
votes
5answers
13k views

Process runs slower as a scheduled task than it does interactively

I have a scheduled task which is very CPU- and IO-intensive, and takes about four hours to run (building source code, if you're curious). The task is a Powershell script which spawns various ...
13
votes
3answers
4k 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 ...
13
votes
1answer
849 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
11answers
8k 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 ...
12
votes
4answers
3k views

Why is 1 of my 24 CPUs Pegged at 100%?

I have an HP ProLiant DL380 G7 system using 2 6-core CPUs, with Hyper-threading enabled, for a total of 24 logical CPUs (as seen by Windows). When running our application, total system CPU ...
12
votes
7answers
3k views

How do storage IOPS change in response to disk capacity?

All other things being equal, how would a storage array's IOPS performance change if one used larger disks. For example, take an array with 10 X 100GB disks. Measure IOPS for sequential 256kb block ...
12
votes
8answers
10k views

Should I completely turn off swap for linux webserver?

Recently my friend told me that it is a good idea to turn off swap on linux webservers with enough memory. My server has 12 GB and currently uses 4GB (not counting cache and buffers) under peak load. ...
12
votes
8answers
14k views

Troubleshooting a “slow” network

We've all had a complaint that the "network" is "slow" at some point: might be localized to one room (switch) or one computer, might just be Internet (DNS? Browser issue?), might be just one ...
12
votes
4answers
5k views

Ubuntu's garbage collection cron job for PHP sessions takes 25 minutes to run, why?

Ubuntu has a cron job set up which looks for and deletes old PHP sessions: # Look for and purge old sessions every 30 minutes 09,39 * * * * root [ -x /usr/lib/php5/maxlifetime ] \ ...
12
votes
7answers
22k views

How can I disable encryption on openssh?

I'm having performance problems using openshh(server) and putty(client) combination to use a remote webproxy. I'd like to disable encryption and test the results to see if it makes a difference. How ...
12
votes
1answer
567 views

ext4 listing of files very slow in one specific directory that contained lots of files before

Background I had a small logrotate misshap... Logrotate would rotate the archived logs by misstake causing a quadratic growth of files in my /var/log/. And by the time I caught wind that something ...
12
votes
2answers
422 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 ...
12
votes
3answers
3k 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
1answer
17k views

Why is my rsync so slow compared to pure cp or even scp?

I'm transfering the files from Linux to Windows 7 via a mounted share (the share is mounted from Windows on Linux).. I'm copying lots of data (i.e. nearly a TB) from the old to the new machine within ...
12
votes
4answers
243 views

tcpdump increases udp performance

I'm running a set of load tests to determine the performance of the following setup: Node.js test suite (client) --> StatsD (server) --> Graphite (server) In short, the node.js test suite ...
12
votes
5answers
15k views

Incredibly slow KVM disk performance (qcow2 disk files + virtio)

I'm having some serious disk performance problems while setting up a KVM guest. Using a simple dd test, the partition on the host that the qcow2 images reside on (a mirrored RAID array) writes at ...
12
votes
3answers
6k views

LVM Performance overhead?

I would be thankfull if someone who understands how LVM works, could tell me a rough estimate, how much slower using LVM (with a Software RAID1) will be. (What I do not want to know how much slower ...
12
votes
9answers
1k views

When to move a virtualized server to physical?

Virtualization has some great benefits, but there are times when a virtualized server needs more performance and should be moved to physical. My question is, how do you tell when these times are? I'm ...
12
votes
1answer
11k views

Is there still a use for irqbalance on modern hardware?

This question has been asked before, but I believe that the world has changed enough for it to be asked again. Does irqbalance have any use on today’s systems where we have NUMA-capable CPUs with ...
12
votes
3answers
2k views

Determining a realistic measure of requests per second for a web server

I'm setting up a nginx stack and optimizing the configuration before going live. Running ab to stress test the machine, I was disappointed to see things topping out at 150 requests per second with a ...
12
votes
1answer
1k views

Why do we get a sudden spike in response times?

We have an API that is implemented using ServiceStack which is hosted in IIS. While performing load testing of the API we discovered that the response times are good but that they deteriorate rapidly ...
12
votes
4answers
614 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
3answers
5k views

Do you use performance counters on production IIS web sites?

Do you keep the counter ON during heavy production loads Which performance counters do you find useful for ASP.Net/IIS 6.0 websites?
11
votes
3answers
14k views

Why is Apache running so many processes? Excessive RAM here?

I notice Apache is running multiple processes on my LAMP server (ubuntu 10.10). I'm just running a Wordpress site with MySQL as a database. It seems like www-data is running apache2 more than it ...
11
votes
1answer
5k views

How do I run my PowerShell scripts in parallel without using Jobs?

If I have a script that I need to run against multiple computers, or with multiple different arguments, how can I execute it in parallel, without having to incur the overhead of spawning a new PSJob ...
11
votes
2answers
550 views

Do unused application pools in IIS affect performance?

Due to a major update in our architecture, we now have a few unused application pools under IIS (there are no web sites mapped to them). I understand how it can a good idea to remove them just to ...
11
votes
2answers
11k views

High disk I/O - jbd2/sda2-8 process

I have run a file server on a CentOS 5.8 final server. My only concern at the moment is what appears to be intermittent but continuous high disk I/O activity causing a general slowdown because of ...
10
votes
6answers
5k views

What purpose does an empty gif (1x1 pix) file serve?

I've seen a few random pages mention using empty gif images to somehow increase performance. I've also found the nginx has a module for just this purpose. What I can't figure out, is exactly how ...
10
votes
4answers
1k views

Why HDD rotate at 7200 rpm?

I was wondering why hard drives rotate at these specific speed (5400,7200, ...) and not other values.
10
votes
10answers
978 views

How does the number of subdirectories impact drive read / write performance on Linux?

I've got an EXT3 formatted drive on a Linux CentOS server. This is a web app data drive and contains a directory for every user account ( there are 25,000 users ). Each folder contains files that ...
10
votes
8answers
5k views

Best file system for external (USB) hard drives/USB memory media

Almost all external USB hard drive and USB memory media/sticks come today preformatted with FAT32. As far as I know the only advantage of the file system is the compatibility among OSes and devices. ...
10
votes
2answers
1k views

Why is my RAID1 read access slower than write access?

I have done some simple performance tests and it seems that reading from my RAID1 is slower than writing: root@dss0:~# for i in 1 2 3; do dd if=/dev/zero of=/dev/sda bs=1048576 count=131072; done ...
10
votes
9answers
2k views

On a modern system, will using disk compression give me better overall performance?

It seems that CPU increases have outpaced disk speed for a while. Assuming a desktop or laptop with modern dual core Intel/AMD CPU and a single average SATA disk, would doing compression on most all ...
10
votes
4answers
612 views

How do I most efficiently store and serve 1,000,000+ small gziped files on a Linux web server?

I have large static content that I have to deliver via a Linux-based webserver. It is a set of over one million small, gzip files. 90% of the files are less than 1K and the remaining files are at most ...
10
votes
2answers
2k views

How does Linux handle concurrent disk IO?

When a Linux server is serving many concurrent requests to read many different files, does it: Seek to File_1, read the entire file, then seek to File_2, read the entire file, then seek to File_3, ...
10
votes
13answers
7k views

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 ...
10
votes
2answers
1k views

Expected performance of e-SATA port multiplication?

For a certain read/write workload, I get 30 MiB/s from a 4-disk array using esata port multiplication. When I move the exact same array to four individual sata connections, I get 90 MiB/s for the same ...
10
votes
1answer
5k views

Is calculating IOPS for ZFS RAIDZ different then calculating IOPS for RAID5 & RAID6?

When calculating IOPS for traditional RAID arrays, one could use the following formula (Borrowed from Getting The Hang Of IOPS v1.3 on Symantec Connect): Ieffective = (n * Isingle) / (READ% + (F * ...