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

learn more… | top users | synonyms (2)

1
vote
2answers
1k views

How efficient is iptables' hashlimit module?

I'm looking for a solution to rate-limit on an ip basis. How many packets can the hashlimit iptables module handle on a recent Intel x86_64 CPU core? 1.000/sec? 1.000.000/sec?
0
votes
1answer
30 views

Managing sudden peak in traffic for event ticketing system

I am going to be managing an event ticketing system for a specific event. I think we will probably be expecting generally low traffic, although there's likely to be a few sudden peaks of traffic (to ...
2
votes
1answer
73 views

Fastest triggering of realtime anti virus scan

I have the problem, that in each backup of my mail system (File based archive on Windows Server 2012 R2), errors occur while backing up virus-infected e-mail attachment files. This is caused by the ...
1
vote
2answers
2k views

MySQL high “sy” (kernel) CPU time

My MySQL server runs about 100 writes and 500 reads per second. The CPU usage looks strange to me. "us" (user) time shows 2-8%, while "sy" (kernel/system) time often shows 50+%. Here's some vmstat ...
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?
0
votes
1answer
29 views

Which bandwith can i expect, when i´m running a SATA SSD on a SAS interface?

So, i know this question had been asked before. I consider to buy a SSD for my Server, because i kinda hate the SAS HDDs in there. I thought: If i connect a SSD, which, in fact, handles way more ...
3
votes
2answers
693 views

optimizing ext[234] for small file throughput

I have a system that has a high throughput of small files on disk, i.e. a huge number of small files are created, written and deleted within seconds. Are there any reasonable ext2/ext3/ext4 mount ...
2
votes
0answers
30 views

Finding or estimating sequential vs random distribution of existing system (VMware / SAN)

IOMeter testing says the IOPs of the storage subsystem can range from hundreds of IOPs for 100% random loads to tens of thousands IOPs for 100% sequential loads. Is there any way I can measure or ...
36
votes
6answers
29k 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 ...
7
votes
1answer
11k views

How is memcache distributed?

I've got memcache running on 5 web servers all of which are on the host list in php and which are load balanced on the front end. So since memcached is supposed to be distributed the php client will ...
2
votes
4answers
7k views

5400 RPM vs. 7200 RPM 2.5" Drives in RAID - Any Real Difference?

Suppose you setup 8 drives in a RAID 10 configuration using 2.5" drives using 500GB capacity each (total 2TB with RAID10 config 1TB useable). The controller (assume a typical 3ware SATA controller) ...
0
votes
0answers
20 views

Oprofile events are not available

I run an Intel(R) Xeon(R) CPU E5520 @ 2.27GHz and I've just started to use Oprofile. I want to measure some events like the BUS_REQ_OUTSTANDING and BUS_TRAN_BRD but are not available. Is ...
-1
votes
4answers
4k views

Improve server performance by configuring MySQL [closed]

I have a server with 8GB of memory, running CentOS 5.4, php 5.2.9, mysql 5.0.77. I have a very large databse of about 20GB (InnoDB and MyIsam tables) and website using it. Website has about 20000 ...
1
vote
1answer
3k views

nginx loading page very slow

I just deployed nginx in a new environment with the same configuration that I've used previously and I am seeing some very odd behavior. Nginx is configured as a reverse proxy for Solr, when I try ...
2
votes
1answer
91 views

Filesystem Performance for LUKS Encrypted Volumes?

As you can format a LUKS volume with any filesystem you want, are certain filesystems better-suited to IO performance against an encrypted filesystem? Specifically, I'm wondering about a loop device ...
0
votes
0answers
38 views

Bad performance on ocfs2 with many files

i am managing a small science server infrastructure with an ocfs2 storage. On the storage are about 9.000.000 files consuming 4,7 TB. The files itself a really small around 500KiB-1Mb. The problem is ...
0
votes
0answers
29 views

Server Specs for browser game that hugs cpu

Our team have developed a web browser game, our servers are using nginx and php-fpm to host the website. the game consist of two parts an api and the game itself. both applications reside on its own ...
3
votes
3answers
18k views

Improving OpenVPN Performance

I've been trying to improve my OpenVPN performance and this is my current setup: cat /etc/openvpn/server.conf port 443 #- port proto tcp #- protocol dev tun #tun-mtu 1500 tun-mtu-extra 32 #mssfix ...
7
votes
1answer
226 views

Extreme ZFS slowdowns after several months

I've got a general-purpose server, providing mail, DNS, web, databases, and some other services for a number of users. It's got a Xeon E3-1275 at 3.40 GHz, 16 GB ECC RAM. Running Linux kernel 4.2.3, ...
0
votes
2answers
65 views

Guest OS 100% utilization, 'Total Run Time' is about 60%

I have ran CPU stress test on linux HyperV VM. Linux reports 100% CPU utilization, but "Hyper-V Hypervisor Virtual Processor(*)\%Total Run Time" metric shows about 60-70%. Is it possible to obtain "...
2
votes
1answer
1k views

High CPU load caused by slow disks?

We are running a online application on a 3-year old server (quadcore Xeon, 4GB RAM, SAN-disks). The server hosts besides the web application a SQL-, FTP-, SFTP, SMTP, and POP-services. Over the years ...
0
votes
0answers
34 views

Comparing 1x Xeon multi core vs 4x UltraSparc IV

I'm in the process of reviewing specs for hardware running an Oracle server. The new hardware will be running using Xeon processor compared to the old servers (Solaris) running on UltraSparc IV. So ...
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 ...
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 ...
1
vote
0answers
138 views

What's your experience with the AWS NAT Gateway performance?

In December/2015 Amazon launched their VPC NAT Gateway service which is basically a managed alternative to creating your own (and it looks very good in comparison to NAT instances). I was just about ...
112
votes
4answers
153k 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-...
1
vote
1answer
16 views

Linux top in RES what does the 't' suffix stand for

When monitoring my system with top, I noticed that under RES some values have a 't' suffix, but I can't see any indication of what this means. PID USER PR NI VIRT RES SHR S %CPU %...
4
votes
1answer
161 views

SQL Azure insert query ten times slower on V12 than V11?

I noticed performance degradation about two weeks ago impacting one of our applications with an SQL Azure backend. It's running on V12 on tier S1 90% of the time, sometimes scaling to S2, S3 or P1. ...
3
votes
1answer
374 views

php-fpm and nginx @ high CPU usage?

My server is with DigitalOcean with the following plan: 2 Core Processor 2 GB Memory My website is receiving thousands of visitors, however, both CPU cores are @ 100%: The issue seems to be with ...
1
vote
3answers
3k views

Unexplicable extreme slowness on Dell PowerEdge R320, fixed only by cold reboot

At this customer's site, there are two new Dell PowerEdge R320 servers with the following configuration: A single 6-core CPU 16 GB of RAM 2x500 GB SATA disks in a RAID 1 array The O.S. is Windows ...
0
votes
0answers
10 views

Performance Impact of a SSD on Jetty

I was wondering if anyone has experience or data if the overall performance of a request is impacted by a SSD when using e. G. Jetty with all necessary data loaded to the RAM. I would expect no ...
8
votes
6answers
3k views

How can I keep Apache from falling over?

I have a pair of servers hosting a single Magento ecommerce site with moderate traffic (60k page views per day reported from google analytics, I think about 80k reported on the server itself). The ...
2
votes
0answers
49 views

What are the various factors that limits disk read and write speeds and on a network? [closed]

How to choose a server which: has high I/O performance of storage is highly flexible in terms of adding more storage So, basically these servers should act as storage servers for OST in lustre ...
1
vote
1answer
130 views

Nginx Stress Test with httperf - Large Data Transfer Differences from Apache Server

I'm running a simple httperf stress test on a quad-core Nginx server, pointed at an HTML/PHP document. Large connection rates quickly begin experiencing high connection and response times (see the ...
1
vote
3answers
4k views

NFS Over OpenVPN: Top Performance Boosters

I have two VPS's - One is running 2008 Server R2 and the other is a Ubuntu 12.04 installation. I am using the Windows VPS for RD sessions for Quickbooks and a couple other apps and using the Ubuntu ...
0
votes
1answer
45 views

Why my disk elevator is set to “deadline”

I have CentOS 6.x Linux server with kernel 2.6.32-573.8.1.el6.x86_64. I did some checks today and I found that disk elevator is "deadline". [root@srv ~]# cat /sys/block/sda/queue/scheduler noop ...
0
votes
2answers
117 views

Apache TLS (SSL) Performance

We are running a fairly powerful dedicated server with a Xeon CPU, 32GB RAM, and RAID SSDs running Centos 6. Yet, we are still seeing HTTPS add over 100ms to our page download time. Is there anything ...
1
vote
0answers
34 views

Persist statistics data from Postgres' stats_temp_directory on demand

We are investigating I/O load in one of our VMs and possibilities to optimize it and it showed that most of the load is generated by the stats collector of PostgreSQL. It jumps between 3,5 and 6,5 MB/...
2
votes
0answers
107 views

Debug slow lan (ssh, nfs) file transfer

I've got two linux boxes attached to a gigabit switch. They both have gigabit NICs, cables are cat7. Testing the network with iperf shows a fast connection but transferring files with rsync, scp, or ...
20
votes
1answer
659 views

Why higher await time for DM multipath device than underlying device?

We have a CentOS 6.4 based server attached to Hitachi HNAS 3080 storage and observed the kernel remount the filesystem in read-only mode: May 16 07:31:03 GNS3-SRV-CMP-001 kernel: [1259725.675814] ...
1
vote
2answers
2k views

Increase download speed of ftp server

I have a VSFTPD server running in my machine. The download speed is about 30 KB/s, which is way less than my connection speed. I understand the upload speed of the server affects the download speed on ...
0
votes
0answers
89 views

Synology DS1813+ RAID 5 with iSCSI IO wait perfomance issue

I'm have RAID 5 on Synology DS1813+ (DSM Version: DSM 5.0-4493 Update 4) with 8 ST4000DM000-1F2168 disk, usind as NAS and iSCSI/NFS targer for ESXi. In low read/write rate from disk have more io wait,...
6
votes
2answers
2k views

Why is Postgres sitting 95% idle, with no file I/O?

I have a TileMill/PostGIS stack running on an 8 core Ubuntu 12.04 VM on an OpenStack cloud. It's a rebuild of a very similar system which was running nicely on very similar hardware (same cloud, but ...
3
votes
1answer
41 views

Finding SQL Server Bottleneck - not CPU, IO, available memory

I'm trying to identify the bottleneck on a new SQL Server implementation (2012 Enterprise). I've been running some meaty queries/ETL jobs which are taking a considerable time - but I'm having ...
2
votes
0answers
62 views

Unexpected discrepancy between write and read performance using cryptsetup 1.4.3 and 1.6.6 on Debian Wheezy (7.9) and Debian Jessie (8.2)

I have been setting up a raid1 array and have set up an encrypted medium using cryptsetup with default options. The raid arrays are supposed to use 2 drives, but for the moment, I only have 1 drive in ...
0
votes
1answer
47 views

MySql ignores memory settings

I'm using MySql community server 5.6 on Ubuntu 15.04, I have /etc/mysql/my.cnf (no other config files). I've made changes to it and restarted MySql. When I use such query SELECT @@key_buffer_size (...
0
votes
0answers
7 views

How to calculate Hardware requirements to send push notifications to GCM [duplicate]

I am gathering hardware requirements for system (up to 100M users) that would be firing Push notifications and nothing more. It would receive a signal to send message and then would select all users ...
0
votes
0answers
66 views

How to find the bottleneck for slow rsync

I want to find the bottleneck for a slow rsync. I see these parts (on byte flow order): IO on source CPU on source Network CPU on destination IO on destination How can I debug this?
0
votes
0answers
50 views

asp.net website intermittent slowness

I have published a asp.net web application in azure which has the configuration of D-13. The domain has been registered with GoDaddy. These are the list of webpages I am using Login.aspx Landing....
1
vote
0answers
148 views

KVM bad IO sync performance in Linux guest

I'm setting up virtualized Ubuntu 15.10 guest inside Ubuntu 15.04 server using libvirt and KVM. Storage in host system: # mount | grep ext4 /dev/sda1 on / type ext4 (rw,relatime,errors=remount-ro,...