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

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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
128 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
294 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
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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
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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
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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
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0answers
45 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
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1answer
98 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
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3answers
3k 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
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1answer
39 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
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2answers
94 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
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0answers
32 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
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0answers
96 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
646 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
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0answers
83 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
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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
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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
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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
38 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
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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
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0answers
55 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
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0answers
43 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
141 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,...
1
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2answers
1k views

Horrible PHP/MySQL Query Performance On Ubuntu Server 10.04

I just did a clear install of Ubuntu Server 10.04 with the standard LAMP config.. Then I made a small script to test insert speeds into a table with 3 columns. When I run the script on any of my ...
0
votes
2answers
1k views

Optimizing disk performance on KVM VM configuration

I have a KVM host server running Ubuntu 12.04 LTS, bare bones installation with only KVM installed. The server has an 8 Core Intel(R) Xeon(R) CPU E3-1230 V2 @ 3.30GHz CPU with 32GB of RAM and SATA ...
0
votes
5answers
153 views

Email server for huge number of subscriber

My question is that my company is thinking of providing a free email account for each of its customers. As a new company we will assume that our corporate email system will be MS Exchange server which ...
0
votes
1answer
29 views

Low iops,read and write performances

We are currently testing our using ZFS on Linux as a storage platform for our VPS nodes but we don't seem to be getting the performance figures we expected. Can you please provide some suggestions as ...
66
votes
8answers
143k 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 ...
2
votes
3answers
82 views

Check the cause of slow loading time among different server

A e-shop has developed using perstashop and put to the three server: the first 2 are amazon EC2, should be same setting Server 1: http://be-pure.com/en/women/3-slim-y-tank.html Server 2: http://52....
3
votes
3answers
2k views

Faster zlib alternatives [closed]

I wonder, if there are any faster builds of zlib around with more advanced optimizations? If it's possible to optimize it using SSE instructions or Intel C++ compiller, or some trick which were ...
1
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2answers
2k views

How to change the scheduler of a RAID 5 device?

I've created a RAID 5 device block by combining 4 HDDs. The name of my device is md1. But the /sys/block/md1/queue/scheduler file outputs "none" on doing cat. And also after editing it using vim ...
0
votes
1answer
104 views

Will adding CPU cores or RAM to my cloud server improve speed in my situation? [duplicate]

I have a Siteground cloud server, and I know nothing about servers. It hosts 8 websites, although 3 of them have their own dedicated IP addresses and cPanels. It's on a Linux server, but there's ...
3
votes
1answer
66 views

Decreased performance of Mysql after superior hardware upgrade

I am quite new to Percona/database servers and i dont know how to approach the following issue. Couple of days ago i upgraded the hardware of a percona cluster (3 nodes) servers with a much more ...
4
votes
3answers
326 views

Generating a lot of dirty pages is blocking synchronous writes

We have processes doing background writes of big files. We would like those to have minimal impact on other processes. Here is a test realised on SLES11 SP4. The server has massive memory, which ...
1
vote
1answer
32 views

What is the “right way” to combine sync and drop_caches?

When I need to do echo 3 > /proc/sys/vm/drop_caches with a sync beforehand, is it better to use sync && echo 3 > /proc/sys/vm/drop_caches or sync ; echo 3 > /proc/sys/vm/drop_caches....
0
votes
1answer
156 views

MongoDB 80,000+ insertions per second

To test my MongoDB 3.2 / WiredTiger on CentOS6, I use the script from http://vladmihalcea.com/2013/12/01/mongodb-facts-80000-insertssecond-on-commodity-hardware/. Here I list the script (a little ...
3
votes
1answer
352 views

CORAID using only 1 of the 2 available NICs for AoE traffic

We got 6 CORAID shelves in my workplace. On 2 of them I see AoE traffic on only 1 of the 2 NICs that are attached to the SAN switch. We got jumbo frames enabled on all devices. Both NICs show up when ...
1
vote
1answer
627 views

MongoDB high CPU usage

Running MongoDB 2.4.11 on Ubuntu 14.04.1 LTS In top, this mongod thread is constantly using ~195% CPU: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 24524 mongodb 20 ...
1
vote
1answer
49 views

Apache - delay over HTTPS but not HTTP

I have a problem with an Apache 2.4.7 on Ubuntu 14.04 (almost default settings), virtual cloud server. On a medium server load (about 2/3.0 cpu usage and tons of free memory) the time for ...
8
votes
2answers
11k views

Slow disk performance on Azure Virtual Machine

Okay, so first of all, allow me to say that I'm not an operations person, but a developer. So I'm going into a bit of unknown land here, so please bear with me. I would like to use a Azure Virtual ...
2
votes
4answers
2k views

Is running a VMware Fusion windows VM from a bootcamp partition faster?

Is running a VMware Fusion windows VM from a bootcamp partition faster than using a virtual drive? If so, is the difference dramatic or just 5-10%
2
votes
2answers
525 views

DRBD terrible sync performance on 10GigE

I've set up a pair of identical servers with RAID arrays (8 cores, 16GB RAM, 12x2 TB RAID6), 3 10GigE interfaces, to host some highly available services. The systems are currently running Debian 7.9 ...
32
votes
2answers
4k views

Why is my bare-metal 16x 2.93GHz cores computer performing poorer than a VPS with 4x 2.5GHz cores?

I have a written a piece of multi-threaded software that does a bunch of simulations a day. This is a very CPU-intensive task, and I have been running this program on cloud services, usually on ...
5
votes
2answers
3k views

cat /proc/cpuinfo shows 3.00GHz model but 1400.000 cpu MHz?

I ran this command on ssh to see CPU info: cat /proc/cpuinfo And it says: ... vendor_id : GenuineIntel cpu family : 15 model : 4 model name : Intel(R) Pentium(R) 4 CPU 3....
0
votes
1answer
130 views

Router - huge difference in Tx vs. Rx

I have two computers: (B) Banana Pi - 1 Gigabit Ethernet, Wi-Fi (supports 802.11n) (D) Desktop PC - 1 Gigabit Ethernet, Wi-Fi (2x2 MIMO, supports 802.11n) And (R) Mikrotik RouterBOARD RB951G-2HnD -...
7
votes
7answers
14k 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 ...
0
votes
2answers
163 views

What does negative value of -1 in kB_rd/ and kB_wr/s mean in PIDSTAT command

This is a sample output from running pidstat. minflt/s majflt/s VSZ RSS %MEM kB_rd/s kB_wr/s kB_ccwr/s 49 0 217532 18784 0.01 -1 -1 -1 Can you ...
4
votes
4answers
248 views

Which VM needs more resources?

I have a physical server which runs 8 virtual machines with virt-manager and kvm. Since one VM is not needed any more, I want to give the remaining virtual machines more resources. I'm looking for ...
0
votes
2answers
123 views

Reduced performance in mysql after upgrade to 5.6.27

Our application was using MySql version 4.0.24 for a long time. We are trying to migrate it to version 5.6.27. But, on testing the performance on 5.6.27, even the simple selects and updates are 30-40% ...