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

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65
votes
8answers
7k 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 ...
51
votes
8answers
100k 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 ...
5
votes
3answers
6k views

mkfs Operation Takes Very Long on Linux Software Raid 5

I've set-up a Linux software raid level 5 consisting of 4 * 2 TB disks. The disk array was created with a 64k stripe size and no other configuration parameters. After the initial rebuild I tried to ...
3
votes
5answers
22k views

Windows networking performance (SMB/CIFS)

Are there registry settings or other settings available to tune Windows networking (SMB/CIFS) performance? I'm trying to get maximum throughput for large file copy operations but any settings would ...
5
votes
1answer
790 views

Is it bad practice to run a web application server directly on port 80/443

I am hosting a web app on amazon aws, using an ec2 instance. On that instance i will be running only one application. using glassfish v3.0.1 I do not want to run the app using : ...
1
vote
3answers
1k views

High Memory Usage on Linux Server

I have a LAMP server with following configuration. CPU : Intel(R) Xeon(R) CPU RAM : 32 GB HDD : 80 GB Running on virtual environment. All the things in the server are running smoothly. But I ...
4
votes
5answers
469 views

is there anyway to know if your supposedly fully dedicated server is really a virtually resource-shared machine? [duplicate]

sometimes I feel my server not responding as smoothly as I would expect (i have a Intel(R) Xeon(TM) CPU 2.80GHz Quad Core), given that for example, the 'top' commands reports a low load < 0.5, CPU ...
44
votes
23answers
68k 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 ...
21
votes
5answers
22k 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 ...
17
votes
5answers
40k views

High load average, low CPU usage - why?

We're seeing huge performance problems on a web application and we're trying to find the bottleneck. I am not a sysadmin so there is some stuff I don't quite get. Some basic investigation shows the ...
21
votes
10answers
19k 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 ...
10
votes
1answer
4k 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 * ...
93
votes
4answers
126k 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 ...
11
votes
7answers
11k 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 ...
16
votes
1answer
19k 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 ...
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: ...
4
votes
4answers
3k views

How can I monitor what process is swapping?

I have a linux webserver. It's running Apache and a python based web application and postgres. It's quite slow. By running ab (apache benchmark) and vmstat I could see that it was swapping while ...
-1
votes
2answers
2k views

Poor SQL performance on HP ProLiant ML310e Gen8 v2 with raid10

I recently bought HP ProLiant ML310e Gen8 v2 server with 8G's RAM and 4 HP 1TB 6G 7.2k rpm SATA (3.5in) Non-Hot Plug MDL HDD disks. It was surprise to me that HP didn't provide debian drivers for ...
-1
votes
1answer
158 views

windows 2003 server slow access

I have a Windows Server with 2 Ethernet ports, both with 1GB cards and I have 20 users connecting to the server to run an application which involves a lot of data being transferred and the speeds are ...
63
votes
13answers
13k 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 ...
17
votes
3answers
14k 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 ...
14
votes
16answers
10k 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 ...
8
votes
7answers
1k views

Good book for building high performance web sites?

Any recommendations for a book about building and running high performance, high-availability web sites on Linux?
8
votes
5answers
19k views

How to improve MySQL INSERT and UPDATE performance?

This question can probably be asked on StackOverflow as well, but I'll try here first... Performance of INSERT and UPDATE statements in our database seems to be degrading and causing poor performance ...
6
votes
9answers
3k views

Linux Server Performance Monitoring

I'm looking to monitor performance on my Linux servers (which happen to be Centos). What are the best tools for monitoring things in realtime such as: Disk Performance I/O, swapping etc.. CPU ...
22
votes
3answers
26k views

Why is my rsync so slow?

My Laptop and my workstation are both connected to a Gigabit Switch. Both are running Linux. But when I copy files with rsync, it performs badly. I get about 22 MB/s. Shouldn't I theoretically get ...
12
votes
11answers
14k views

A monitoring tool that captures processes' memory usage/cpu usage, etc over time

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 ...
16
votes
3answers
7k views

OpenVPN performance: how many concurrent clients are possible?

I am evaluating a system for a client where many OpenVPN clients connect to a OpenVPN server. "Many" means 50000 - 1000000. Why do I do that? The clients are distributed embedded systems, each ...
14
votes
8answers
6k views

Doing an rm -rf on a massive directory tree takes hours

We're using rsnapshot for backups. It keeps lots of snapshots of the backuped up file, but it does delete old ones. This is good. However it's taking about 7 hours to do a rm -rf on a massive ...
4
votes
3answers
4k views

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 ...
3
votes
6answers
9k views

IO Wait causing so much slowdown (EXT4 JDB2 at 99% IO ) During Mysql Commit

I am writing an indexer, using python, which indexes documents and insert them into Database, Before it was single process but now i made it to multiprocessing with 4 parallel processes running.After ...
7
votes
4answers
3k views

Experience in migrating from Apache to nginx?

I'd like to get some feedback about a migration From Apache to nginx. My goal is to reduce the memory footprint of the web server. Currently, I use the following modules.features on Apache: multiple ...
6
votes
6answers
7k views

How many files in a directory is too many? (Downloading data from net)

Greetings, I'm writing some scripts to process images from various photo websites. Right now I'm storing all this data in individual text files in the same directory. The directory is web ...
3
votes
2answers
17k views

Find out the bottleneck for windows remote desktop server (Terminal server)

I have Windows server 2008 R2 (SP1) installed on my VMware Host to work as RDS server. Sometimes my remote users can see the lagging/delay on RDS server. Can anyone tell me from their experience what ...
1
vote
3answers
3k views

How to find out if my Windows Server 2003 needs more memory?

What's the best way to find out if my server needs more memory? I suppose I should use Perfmon, but which counters? Thanks.
7
votes
1answer
4k views

Remote connection to MySQL server takes very long

I have a MySQL 5.0.75 server running on my Linux notebook to which I want to connect from another machine in the local network. This connection takes 5-6 seconds: mysql -h 172.22.65.101 -u myuser ...
5
votes
7answers
10k views

Speeding up rsync over smb

I'm backing up a Linux box over SMB to a NAS. I mount the NAS locally and then I rsync a lot of data (100GB or so). I believe it's taking an awfully long time to do it: more than 12 hours. I would ...
3
votes
3answers
2k views

Apache performance issue, after “1000 total children” Apache no longer responds to HTTP requests. Not MaxClients issue?

Hoping someone can point me in the right direction as I've spent the last week trying to figure out where the "issue" is but haven't been able to, tried posting to the Apache users mailing lists but ...
3
votes
2answers
390 views

MediaWiki is getting slower gradually

I set up my MediaWiki on a CentOS. In the first few months, it works fine and fast. But it seems gradually getting slower. My wiki site has less than 50 pages, so it's a very small scale site. But it ...
6
votes
6answers
2k views

Windows 2008 Server on mixed ethernet speeds — download from share slow, but fast plain TCP

I have a Windows Server 2008 R2 x64 server that is AD controller and file server. I have a problem that Windows XP clients experience terribly slow (less than 10Mbps, really less than ...
4
votes
1answer
689 views

iotop and iostat disagree

I'm trying to understand what's going on with my server's disks. It's running Ubuntu 12.04LTS and I'm used to using iostat to know when the disk is the bottleneck. But iostat -xd looks to me like ...
4
votes
2answers
2k views

Is there any way to limit bandwidth usage by process ID in Windows?

Is there any way to basically do traffic shaping based on process ID or name within a Windows instance?
2
votes
1answer
7k views

ESXi 5 network performance is slow

We just did a fresh install of ESXi 5 on a host that was running ESX 4 before. Nothing has changed hardware wise. After the upgrade network performance is much slower. Even copying a big file from one ...
2
votes
4answers
1k views

Storing / calculating historical load averages

When I run uptime, I get output similar to the following: 07:50:39 up 13 days, 5:00, 1 user, load average: 0.00, 0.02, 0.00 Is there a way, other than by running uptime every X-many minutes, to ...
1
vote
4answers
255 views

file share system architecture asking for advice

I am using Windows platform to setup a web based file share system. In more details, individual users could upload and share documents from web interface (content may be big document, like video ...
8
votes
3answers
5k 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 ...
6
votes
5answers
4k views

How to measure disk throughput?

I want to know how many bytes per second can I write to the disk and read from it. How can I do that on linux machine?
3
votes
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 ...
3
votes
7answers
6k views

Copying large file to remote server causes it to run out of physical memory

I have a strange issue that appears to have started recently. When I copy a large file (Approx 6GB) from my laptop to one of our older fileservers the server runs out of memory after a few seconds. ...
1
vote
2answers
244 views

Microsoft Windows server monitoring tools

I'm more of a developer then an IT guy and I was wondering if there are any existing Microsof tools for monitoring servers and potentially SQL Server. We have access to MSDN so anything created by ...