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

learn more… | top users | synonyms (2)

16
votes
5answers
28k 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 ...
16
votes
3answers
20k 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 ...
16
votes
2answers
2k views

Is running permanently in a VMWare snapshot bad for performance?

I understand that the VMWare KB frowns upon long running snapshots mainly due to two things (In my opinion) Taking tons of snapshots can fill up the data store. Snapshots are simply delta files. ...
16
votes
4answers
21k views

How can I find out what is causing interrupts on Windows?

Occasionally I come across servers (Windows 2003 and 2008) with high processor % interrupt time. Is there a way to see what program or device is causing the interrupts?
16
votes
1answer
297 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 bytes/...
15
votes
8answers
14k 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. ...
15
votes
2answers
31k 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 ...
15
votes
8answers
23k 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 ...
15
votes
3answers
4k 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 (...
15
votes
8answers
10k views

How to scale php5+MySQL above 200 requests/second?

I am tweaking my homepage for performance, currently it handles about 200 requests/second on 3.14.by which eats 6 SQL queries, and 20 req/second on 3.14.by/forum which is phpBB forum. Strangely ...
15
votes
4answers
1k 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 ...
15
votes
4answers
4k 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: ...
15
votes
3answers
3k 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 ...
14
votes
11answers
5k 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. ...
14
votes
5answers
34k views

Howto check disk I/O utilisation per process

Im having a problem with a stalling Linux system and I have found sysstat/sar to report huge peaks in disk I/O utilization, average service time as well as average wait time at the time of the system ...
14
votes
4answers
8k views

Performance difference between ramfs and tmpfs

I need to setup an in memory storage system for around 10 GB of data, consisting of many 100 kb single files(images). There will be lots of reads and fairly periodic writes(adding new files, deleting ...
14
votes
10answers
7k 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 ...
14
votes
2answers
1k views

Virtualization - Ten 1Gbps links or one 10Gbps link? (Performance)

I have a machine that has several VM's (5) and 3 physical networking cards (with each 2 ports), with a total of six 1Gbps ethernet ports. I have a SPF-capable switch, having a total of 48Gbps ...
14
votes
4answers
2k views

How do limit disc i/o during backup?

I have a cron that basically do a simple "tar zcf" in the night. The server has: 8 Cores - Intel(R) Xeon(R) CPU E5606 @ 2.13GHz 25GB RAM Ubuntu 12.04.2 LTS Hardware RAID 1 (LSI Logic / Symbios ...
14
votes
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
506 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
2answers
9k views

See what files are being written to (like iotop but for files, not processes)

I have a Linux server, and it's doing a lot of disk io. There is one process that is doing most of the disk writes. I found this out with iotop, which shows the processes that are doing disk I/O. Is ...
14
votes
3answers
5k 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 ...
14
votes
3answers
970 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
3k 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 ...
14
votes
2answers
18k 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 ...
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 ...
13
votes
14answers
16k 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
1answer
16k 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 ...
13
votes
2answers
6k views

Can rsync display current average speed?

When I'm transferring large quantities of data using rsync, it would be helpful if I could have the average speed up until now at a glance, rather than a bunch of different speeds for each file.
13
votes
1answer
6k 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
2answers
435 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 ...
13
votes
1answer
19k 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 ...
13
votes
1answer
1k 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
10k 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
4k 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
3answers
2k views

What does “low profile” stand for, connected to hardware?

When it comes to hardware I often read something like "Apple Mac computers, and other lower profile ...." For me it sounds like a better word for low end segment hardware but I am not sure about it. ...
12
votes
7answers
6k 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
3answers
6k 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?
12
votes
6answers
6k 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 ...
12
votes
4answers
1k views

Load time impact of htaccess

There are in general two possibilities of handling stuff on Apache: make configurations for folders one by one using htaccess file to fully resign htaccess and put all the rules into the httpd.conf ...
12
votes
3answers
2k views

Configuring a router to drop packets, introduce latency, corrupt data

I was wondering if anyone had any experience setting up an environment designed purposefully for poor performance when sending/receiving requests over a network. I'm developing an application and ...
12
votes
1answer
836 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
4answers
6k 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
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, ...
12
votes
2answers
10k views

Rabbitmq - Reasonable performance/scale expectations

I'd be grateful if anyone could point me in the direction of some reasonable scale figures/limitations on rabbitmq (on "average" hardware, fwiw) or post your experience with its performance. I'm ...
12
votes
4answers
8k 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
4answers
569 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 ...