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

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6
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2answers
183 views

Calling sync/fsync slows IO after 30 minutes uptime

After 30 minutes of uptime using Ubuntu 14.04 with an ext4 hybrid SSD I see many processes blocking IO using iotop. The root cause of this slowdown has been traced back to the Unix system call sync. ...
6
votes
2answers
812 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 ...
6
votes
1answer
2k views

Does APC really improve performance with PHP 5.3+

According to a Linux Adminstrator over at Hostgator: With PHP 5.3 having APC installed is not needed as PHP 5.3 already has improvements that APC does resolve in it. Is that statement actually ...
6
votes
1answer
4k views

Nginx auto minify html output

does anyone know of a way to get nginx (or any other method) to minify html output on the fly? It seems straightforward to me and can shave a few kb off and help speed up the site.
6
votes
3answers
665 views

A strategy for network monitoring to improve network health?

The goal is to find out which parts of network should be upgraded / reorganized to improve network health (reliability and performance). What are the methods to monitor network traffic, detect ...
6
votes
3answers
4k views

Apache + Tomcat VS Stand Alone Tomcat or GlassFish

I am setting up a Debian server to serve Java web applications. I have done quite a bit of research for several weeks now. Tomcat's web site says it is better to use stand alone Tomcat for speed if ...
6
votes
4answers
528 views

Best performance: 1tb vs larger drives in app using only sequential read/writes

I have a custom app that is multi-threaded; each thread runs on its own logical core (the workstation is a dual xeon, with 12 physical and 24 logical cores). So there are 24 threads running ...
6
votes
4answers
1k views

My linux server takes more than an hour to boot. Suggestions?

I am building a CentOS 5.4 system that boots off a compact flash card using a card reader that emulates an IDE drive. It literally takes about an hour to boot. The ultra-slow part occurs when Grub ...
6
votes
2answers
4k views

Relation between disk IOPS and sar tps

I'm trying to estimate IOPS requirements of my application running on 32-bit CentOS 6.2. I started to take some measurement on a machine with SATA disks and I'm quite confused of difference between ...
6
votes
1answer
1k views

Very uneven CPU utilization with SQL Server 2012 on 2 processor computer with 16 cores / processor

After installing SQL Server Enterprise 2012 with the Server + Cal license model, on a computer with 2 processors each with 16 cores (and no hyperthreading involved) and putting the server under ...
6
votes
1answer
1k views

ext3 file system performance tuning: what metrics to monitor

I have a high-IO application that is working, and scaling well to date. Over the past few months we've been trying to look down the road and predict where our next bottlenecks will occur. One of ...
6
votes
4answers
4k views

iotop shows kswapd0 at 99.99% with 0% DISK READ and DISK WRITE

I have a heavy postgres query. It takes over ten minutes to run. I'd like to upgrade my hardware to get it run faster. I think more RAM will help, but my motherboard is full so I'll need a whole ...
6
votes
1answer
2k views

Why do I see a large performance hit with DRBD?

I see a much larger performance hit with DRBD than their user manual says I should get. I'm using DRBD 8.3.7 (Fedora 13 RPMs). I've setup a DRBD test and measured throughput of disk and network ...
6
votes
1answer
2k views

windws server 2008 udp multicast performance problem

I encounter a strange performance problem on 2008 R2 Enterprise SP1. Here is the setup: Many processes listening to distinct Multicast UDP streams (5 multicasts listen by process) bound on a single ...
6
votes
1answer
1k views

IPSec software that can use multiple CPU cores

Can anyone recommend a good IPSec software that can use multiple CPU cores to achieve performance ~2Gbps on Linux dual-CPU quad-core E5620 Xeon setup (total 16HT cores)? I have tried OpenSwan and ...
6
votes
0answers
84 views

Fast distributed filesystem for a large amounts of data with metadata in database [closed]

My project uses several processing machines and one storage machine. Currently storage organized with a MSSQL filetable shared folder. Every file in storage have some metadata in database. Processing ...
6
votes
4answers
7k views

3.5“ 15k RPM drives vs 2.5” 10k RPM drives

How do 2.5" 10k RPM SAS drives perform compared to 3.5" 15k RPM SAS drives? Specific areas of comparison: Random write Random read Sequential write Sequential read
5
votes
7answers
9k views

How to optimize performance for MSSQL databases?

I'm a dba with a database with ~280 tables, and total datasize of ~1,5GB. I'd like to tune the database to make it perform better. What do you do to keep your SQL databases performant? How much ...
5
votes
3answers
15k views

Measure Linux IOPS for a running system

How do I measure IOPS of a running Linux server? I know that the theoretical IOPS of a SATA drive is around 90 and enterprise 10k SAS/FC disk is 180. I want to know how much my running system is using ...
5
votes
7answers
2k views

setup lowcost image storage server with 24x SSD array to get high IOPS?

I want to build let's name it a lowcost Ra*san which would host for our social site the images (many millions) we have 5 sizes of every photo with 3 KB, 7 KB, 15 KB, 25 KB and 80 KB per Image. My ...
5
votes
7answers
11k 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 ...
5
votes
12answers
1k views

Optimum way to serve 70,000 static files (jpg)?

I need to serve around 70,000 static files (jpg) using nginx. Should I dump them all in a single directory, or is there a better (efficient) way ? Since the filenames are numeric, I considered having ...
5
votes
5answers
825 views

Linux: how many disk I/O does it take to read a file? How to minimize it?

According to this paper on Facebook's Haystack: "Because of how the NAS appliances manage directory metadata, placing thousands of files in a directory was extremely inefficient as the ...
5
votes
4answers
6k views

How do I configure RAID 5, especially stripe size, with 24 x 1.2 TB drives for CentOS 6?

For a Dell R920 with 24 x 1.2TB disks (and 1TB RAM), I'm looking to set up a RAID 5 configuration for fast IO. The server will be used to host KVM VMs that will be reading/writing files of all sizes, ...
5
votes
3answers
478 views

Should I host my entire web application using https?

Actually my only requirement for using SSL encryption is that when a user logs in, the password is transferred encrypted. However after reading a bit about protocol switching, that an HTTPS session ...
5
votes
6answers
592 views

Sysadmin performance metrics?

I work at a dot com and part of our team's responsibility is to maintain the production web application and server farm. Only recently did our department even get created, and now we have a huge ...
5
votes
4answers
13k 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 ...
5
votes
8answers
7k views

Hard Drive Speed: RPM vs. Cache

When trying to choose a SATA magnetic hard drive (not SSD) for high performance for both random and linear access, which should be the primary factor? For example: would a 10k RPM drive with 16MB ...
5
votes
4answers
8k views

Virtual Machine guest optimization tips

I've installed Windows7 in VirtualBox 2.2.4 and worked like a charm. But compared with my WindowsXP virtual machine, the performance is slow. I've installed Windows7 in (non-virtual) machines and the ...
5
votes
6answers
847 views

How to do periodic Sql Server performance monitoring and troubleshooting?

What are the best tools and processes for periodically monitoring and troubleshooting sql server performance issues?
5
votes
2answers
4k views

In absense of iotop which command is most appropriate for get i/o bounded process

Suggest me best way to list io bounded process. I know iotop is best way to get list but want any alternate option since my system showing a large number of D state process.
5
votes
4answers
584 views

Is there an advantage to load balancing using multiple VMs all on the same hardware?

Some collegues are suggesting a web load balancing schema with multiple web servers (IIS7) on different virtual machines all running on the same hardware. Is this a truly advantageous setup? All ...
5
votes
2answers
6k views

Clustered indexes versus non-clustered indexes?

I am in charge of a smaller DB 300+ hundred megs 100'ish tables about 45 users hit it throughout the work day. Mostly reads, but a fair number of updates and inserts. I have been slowing learning the ...
5
votes
4answers
3k views

dd vs. secure-erase for reconditiong SSDs

Does writing zeros to an entire ssd (dd if=/dev/zero of/dev/sdX) give the same performance restoring effect that you get from a "secure erase", or does secure erase do something else as well? ...
5
votes
5answers
6k views

Hyper-V Requirements, disk partitioning

My rule of thumb for a physical server was fast random access disk (VelociRaptor/SSD) for OS, and large disks for data (e.g. WD Caviar). How does that look for a Hyper-V that should run two virtual ...
5
votes
7answers
3k views

What is faster? A local mechical hard drive or a solid state drive over gigabit ethernet?

SSDs are rather new, so I couldn't find this information on the Internet. Would the performance of a local hard drive connected using SATA2 get out performed by a SSD over gigabit ethernet? In terms ...
5
votes
3answers
7k 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 ...
5
votes
2answers
2k views

ZFS with L2ARC (SSD) slower for random seeks than without L2ARC

I am currently testing ZFS (Opensolaris 2009.06) in an older fileserver to evaluate its use for our needs. Our current setup is as follows: Dual core (2,4 GHz) with 4 GB RAM 3x SATA controller with ...
5
votes
1answer
1k 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.
5
votes
1answer
915 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 : ...
5
votes
4answers
687 views

Geographical DB synchronus mirroring

An architect in our company has designed a solution based on 64 bit SQL2005 Standard edition synchronous mirroring between a physical (4 quad core, 32GB RAM) server and a virtual DR server (4 virtual ...
5
votes
1answer
938 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 ...
5
votes
1answer
4k views

HP DL380 G7 + Smart Array P410i + sysbench -> poor raid 10 performance

I have running system with low IO utilization: HP DL380G7 ( 24gb RAM ) Smart Array p410i with 512mb battary backed write cache 6x SAS 10k rpm 146gb drives in RAID10 Debian Squeze linux, ext4 + LVM, ...
5
votes
1answer
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 ...
5
votes
3answers
2k views

How valuable is TCP Window Scaling?

On a busy† Debian Lenny server of mine I am considering disabling TCP Window Scaling. Why? I'd like to enable syn cookies, which disables TCP Window Scaling. This server is locally firewalled and ...
5
votes
5answers
2k views

PostgreSQL High Performance Setup

I am setting up a server with the following specs: * Qty 4 Processors (AMD Opterons with 12 cores each) * 32 GB Memory * Qty 8 HDD (15K SAS Dual Port) * CentOS 5.5 * JBoss * PostgreSQL It is likely ...
5
votes
4answers
2k views

SSD drives and RAID configurations vs LVM

Background: I'm familiar with the basic RAID levels, and am curious to know if using SSD devices in a RAID0 or RAID5 would be a better deployment than adding them to a large LVM volume. ...
5
votes
3answers
8k views

Configuring Varnish to rewrite Expires/Cache-Control headers for client-side caching

How do I configure Varnish so that all responses to requests matching say "*.css" gets cached in the client's browser for 30 days? What I'm trying to achieve is making Varnish set the correct ...
5
votes
2answers
584 views

Very active database with high % disk times

I have a very active website which is using a NoSql database (RavenDb). I don't have exact figures as i'm not quite sure how to extract this information (any help would be great!) But looking in ...
5
votes
6answers
12k 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 ...