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Questions tagged [performance]

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

101
votes
8answers
19k 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 ...
71
votes
6answers
92k views

Software vs hardware RAID performance and cache usage

I've been reading a lot on RAID controllers/setups and one thing that comes up a lot is how hardware controllers without cache offer the same performance as software RAID. Is this really the case? I ...
8
votes
1answer
2k 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 : www.mydomain.com:...
89
votes
8answers
181k 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 ...
7
votes
3answers
16k 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 ...
32
votes
11answers
27k 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 ...
15
votes
4answers
3k 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 ...
8
votes
3answers
16k 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 ...
86
votes
25answers
145k 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 ...
25
votes
5answers
30k 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 ...
26
votes
4answers
25k views

Limit Linux background flush (dirty pages)

Background flushing on 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 (/proc/sys/vm/...
13
votes
5answers
11k views

How can I replay Apache access logs back at my servers to do real world load testing?

I looked at Tools for load-testing HTTP servers? but I couldn't see how to replay my own existing logs in any of those tools. I have a bug that only occurs under certain load operations which my ...
5
votes
7answers
44k 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 ...
2
votes
3answers
6k 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 ...
-1
votes
2answers
4k 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 ...
77
votes
6answers
175k 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 ...
14
votes
1answer
49k views

How to troubleshoot latency between 2 linux hosts

The latency between 2 linux hosts is about .23ms. They are connected by one switch. Ping & Wireshark confirm the latency number. But, i dont have any visibility into what is causing this latency. ...
11
votes
1answer
14k 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 * ...
20
votes
8answers
40k 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 ...
28
votes
4answers
45k 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
6answers
41k 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 ...
19
votes
1answer
32k 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 ...
7
votes
6answers
9k 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 ...
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: ...
3
votes
1answer
63k views

Mysql showing 100% CPU usage [closed]

I'm experiencing some problems with my MYSQL server installed with Cpanel. My server is showing 100% usage of mysql even if I don't have too much traffic on web. I am running CentOS 6.5x64 with 80GB ...
4
votes
2answers
7k views

Samsung 850 EVO + HP P410 limited iops?

I´m experiencing a weird write iops limitation with a HP P410 256mb cache controller and 4x consumer grade ssd´s (Samsung EVO 850) in RAID5/10. After upgrade to latest firmware (6.64) for HP P410 ...
3
votes
4answers
2k views

Azure IO performance

We have a number of Windows Server virtual machines that we use for .NET and Java development and QA. I find Azure attractive for the obvious reasons but mainly for the opportunity to reduce non-...
-1
votes
1answer
188 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 ...
127
votes
4answers
171k views

FreeBSD performance tuning: Sysctl parameter, 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 100,000-...
123
votes
13answers
49k 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 ...
32
votes
4answers
39k 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 ...
13
votes
5answers
46k 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 ...
35
votes
17answers
66k views

What network file sharing protocol has the best performance and reliability? [closed]

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 ...
40
votes
4answers
87k 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 ...
29
votes
7answers
20k 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.
43
votes
11answers
76k 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.
19
votes
7answers
39k 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 ...
10
votes
2answers
68k 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 ...
7
votes
9answers
5k 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 ...
20
votes
8answers
15k 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 ...
27
votes
4answers
34k views

Why VM snapshots are affecting performance?

I read in one of the VMware KB articles that snapshots will directly affect VM performance. But my team keeps asking me how snapshots can affect performance. I would like to give them solid reason ...
22
votes
8answers
18k 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. ...
16
votes
2answers
2k 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 ...
4
votes
6answers
762 views

Recommended website performance monitoring services? [closed]

I'm looking for a good performance monitoring service for websites. I know about some of the available general monitoring services that check for uptime and notify you about unavailable services. But ...
17
votes
5answers
17k 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 ...
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 ...
8
votes
7answers
21k 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 ...
7
votes
1answer
4k 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 ...
1
vote
3answers
4k 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.
10
votes
1answer
8k 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 -...