26 votes
Accepted

Maximizing rsync performance and throughput - directly-connected gigabit servers

The file count and SSH encryption overhead are likely the biggest barriers. You're not going to see wire-speed on a transfer like this. Options to improve include: Using rsync+SSH with a less costly ...
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  • 194k
19 votes
Accepted

Evaluating the CPU I/O wait on Linux

You need to be careful when evaluating these figures. IOWait is related, but not necessarily linearly correlated with disk activity. The number of CPUs you have affects your percentage. A high IOWait ...
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  • 22.6k
15 votes

At what point is a server considered idle?

A machine is idle when it's not performing the task it's supposed to perform for lack of requests. For example, if you had an email server, you could determine if it was fielding any requests from the ...
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  • 6,961
10 votes
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Nginx "ssl_stapling" ignored, no OCSP responder URL in the certificate

The ssl_trusted_certificate option should point to the root certificate and all intermediate certificates of the CA, not your signed certificate. This is made clear in the NGINX documentation here ...
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9 votes
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Minimal upgrade from one minor CentOS version to the next

No. Not really. If you're running the upgrade, that means new GLIBC and kernel and supporting packages will be downloaded and installed. In addition, any updates to the packages already present on ...
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  • 194k
8 votes

At what point is a server considered idle?

"Idle" is not a black and white concept: even a busy server can have free CPU cycles, IOPs and memory to run some other application. As a rule of thumb, target CPU load should be at around ~80% and ...
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  • 43.1k
7 votes
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What is a core, and will purchasing more cores for my VPS speed up page load times?

You might know what a core is from shopping for desktops and laptops. It's the CPU, the processor, the bit that does the work. Here's a wikipedia link that might help. I plugged your site into this ...
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6 votes

My Vps is too Fragile

The $5 VM cannot hold a full cPanel installation. A few suggestions: Configure MySQL to use the minimum settings example .cnf Disable all unnecessary modules in Apache and tune the number of Max/Min/...
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6 votes

Red Hat Linux tuning for a single application with a few TCP clients

Performance tuning is as much a black art as it is a science. Complete books have been written about it, include quite a bit as part of the vendor documentation You start with good monitoring, add ...
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  • 70.6k
6 votes
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Track what is causing AWS RDS to use insanely high bandwidth

You should always use the private IP addresses to communicate between your various infrastructure components (RDS, ElastiCache, whatever). If you use the public IP address, then you will be billed for ...
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6 votes
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LVM cache in writeback mode is equivalent to external ext4 journal?

An external journal isn't the same thing as an LVM cache device at all. An LVM cache on an SSD for writeback wouldn't be volatile, so the concerns with data integrity aren't enormous (except for if ...
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  • 6,961
5 votes
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RAID 10 Stripe Size for XenServer

I am going to try and sum up my comments into an answer. The basic line is: You should not tinker with the strip size unless you have good evidence that it will benefit your workload. Reasoning: For ...
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  • 40.2k
4 votes

Maximizing rsync performance and throughput - directly-connected gigabit servers

As you probably know copying a lot of little files (eg mailboxes using MailDir format or similar) is definitely not the best option to take advantage of high bandwith interfaces. SSH is probably not ...
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  • 1,600
3 votes

Possibility of WAN Optimization for SSH traffic

Definitely see the answers at: Why is my rsync so slow? I've relied on rsync-based solutions for replication and backup for many years. I've never needed to use any form of WAN acceleration (using an ...
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  • 194k
3 votes

Possibility of WAN Optimization for SSH traffic

I was initially going to be a naysayer to the idea of trying to "WAN optimize" rsync traffic, but the more I thought about it the more I decided that it was possible. A TCP-based dictionary ...
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3 votes
Accepted

Nginx performance when running multiple instances on the same machine

From a system point of view, there is no inherent differences in running 4 masters with 4 server sections, or a single master with 16 server sections. It implements the same architecture : ...
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  • 656
3 votes
Accepted

Speed up backup of just ACLs on large file systems

In my experience, getfacl can be CPU bound by the username-resolving process. Try adding the -n switch, for example issuing getfacl -n -R -p /backup/dir > out_file During benchmarks, pay special ...
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  • 43.1k
3 votes
Accepted

winbind authentication through apache slow

I still didn't find how to improve the performance when using mod_authnz_external. However changing to another apache module mod_authnz_ldap got rid of the performance problem. The only downside then ...
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  • 784
3 votes

Joins performed without indexes: 5568

Joins performed without indexes: 91. This is most likely the biggest culprit for your performance. Your database doesn't have proper indexes for columns that are used in SQL queries that join data ...
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3 votes
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Debugging and fine-tuning the linux process scheduler

Is it correct that the php-fpm process spent as much as 58.130 ms waiting for a CPU to run on? it's time from wake-up to context switch, so I'd say it's time taken to make it finally running (thus — "...
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  • 9,113
3 votes

XFS with No Barrier Mount option deprecated

Since kernel 4.13, the nobarrier was removed for XFS. This article suggests two workarounds: switch from XFS to ext4 echo "write through" > /sys/block/$device/queue/write_cache I tried myself the ...
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  • 213
3 votes
Accepted

Very slow write speed (NVME drive) on 10G network

This answer was inspired by comment by @shodanshok, who commented (so I can't upvote his contribution -- posting an answer instead) Edit 2021/06/09 - iperf3 developers identified a possible problem; ...
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  • 191
3 votes
Accepted

NGINX Redirect to Cached File in Subfolder

You can use a regular expression location to extract the first and second parts of the URI. Use a try_files statement to search the file system for each file in order. For example: location ~ ^(/...
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2 votes

Optimize images on CentOS server

You can use the file command to determine what the extension should be file -b --mime-type a image/jpeg file -b --mime-type c image/gif So it should be fairly straightforward to loop over the files ...
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  • 113k
2 votes

Optimize images on CentOS server

Is there a reason you can't install ImageMagick? I'm assuming that's what you're looking at, since you have this question tagged as such - if so, my instinct would be to simply run something akin to: ...
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  • 8,860
2 votes

Config NGINX to GZip Font Files? ( Different gzip_types for different directories)

CloudFlare will only gzip TTFs if they are transferred with one of these mime types: font/ttf application/ttf application/x-ttf Source: https://support.cloudflare.com/hc/en-us/articles/200168396-...
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2 votes
Accepted

Nginx auto minify html output

Google Pagespeed for Nginx does minification, and a bunch of other things. However when I benchmarked it didn't make enough of a difference to bother with, given my site was already well optimized. ...
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  • 29.2k
2 votes

My Vps is too Fragile

The sites themselves may not be so big, but just running apache (and php) and mysql and the OS can exceed your allotted ram (which you're doing, see your swap usage) if you don't take measures to ...
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  • 637
2 votes

What is the Ideal value for Worker Processes in Nginx Config?

Some other programs uses cpu, like php maybe? Paste all your top output, not only your cpu, but programs too. Turn on visibility of threads too... (H key, if I remember correctly.)
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2 votes

Slow disks but lots of RAM - optimization tips?

There is nothing you CAN do. Disc cache size - Windows automatically uses all non-app-allocated memory, so - there you go. Page file - should not do a lot anyway (only swap out stuff really not used). ...
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  • 50.7k

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