Questions tagged [cache]

A location or process for storing of transitory or temporary data in order to improve application or system performance.

Filter by
Sorted by
Tagged with
6 votes
3 answers
18k views

What is the memory module on a RAID card needed for?

As above, what is the reason for needing a memory module on a RAID card? The card I am looking at (HP P410) comes with either 256MB or 512MB but unsure which to get and why.
Tom's user avatar
  • 88
6 votes
2 answers
9k views

Non-volatile cache RAID controllers: what kind of protection is there against NVCACHE failure?

The battery back-up (BBU) model: admin enables write-back cache with BBU writes are cached to the RAID controller's RAM (major performance benefit) the battery saves uncommitted and cached data in ...
astrostl's user avatar
  • 690
93 votes
16 answers
71k views

Why drop caches in Linux?

In our servers we have a habit of dropping caches at midnight. sync; echo 3 > /proc/sys/vm/drop_caches When I run the code it seems to free up lots of RAM, but do I really need to do that. Isn't ...
ivcode's user avatar
  • 1,072
17 votes
1 answer
7k views

deleting linux cached ram [duplicate]

I have a webserver that has 8GB of ram and is running a pretty intensive php site (1 site) that does file manipulation, graphing, emailing, forums, you name it. The environment is far from static ...
Patrick R's user avatar
  • 2,975
97 votes
18 answers
91k views

Caching/preloading files on Linux into RAM

I have a rather old server that has 4GB of RAM and it is pretty much serving the same files all day, but it is doing so from the hard drive while 3GBs of RAM are "free". Anyone who has ever tried ...
Andrioid's user avatar
  • 2,700
4 votes
1 answer
5k views

Two separate PHP-FPM sites seem to be using the same code?

I have two websites with two codebases, yet when I change one codebase, I see the change in both. I have two checkouts of the same website. They are set up to use PHP-FPM through Apache2 with FastCGI....
Sander Marechal's user avatar
2 votes
1 answer
1k views

Varnish cache with Nginx SSL termination

How can I use varnish cache with nginx SSL termination for my SSL-Only (Https only) website? I use ubuntu 18.04 and I am currently running a wordpress site on my server.
Rahul Biswas's user avatar
21 votes
5 answers
15k views

Is there a way to get Cache Hit/Miss ratios for block devices in Linux?

Is it possible to see in Linux how many read and write requests from user space end up causing cache hits and misses for block devices?
Kyle Brandt's user avatar
  • 84.3k
15 votes
6 answers
13k views

SATA Disks that handle write caching properly?

It's pretty common to see advice to disable the write cache on individual disks used for databases because otherwise some disks will acknowledge writes that haven't yet made it to the disk surface. ...
eas's user avatar
  • 268
122 votes
8 answers
418k views

How do I clear Chrome's SSL cache?

I have a HAProxy / stunnel server that handles SSL for our sites on AWS. During testing, I created a self-signed cert on this server and hit it from my desktop using Chrome to test that stunnel was ...
Foovanadil's user avatar
  • 1,320
97 votes
5 answers
111k views

Disable caching when serving static files with Nginx (for development)

We are using Nginx to serve static files on a development platform. As it is a development platform, we'd like to disable caching so that each change is propagated to the server. The configuration of ...
Olivier Chappe's user avatar
30 votes
7 answers
152k views

How do I force NGINX to load new static files?

I recently pushed a major update to a site and I'm having an issue where some people can't log in because their browser is loading old javascript files. Some of the things I have done include: Cache ...
jwerre's user avatar
  • 778
26 votes
2 answers
20k views

Linux SSD as HDD cache

I have a Linux server system installed on an SSD and an HDD for user data. As there is space left on the SSD, I want to use it as a read cache for the HDD. Looking at the possibilities, I found: dm-...
GxB's user avatar
  • 431
24 votes
2 answers
35k views

Varnish Cache - default TTL?

I have discovered that I can set the TTL in Varnish as follows in my VCL file: sub vcl_fetch { # 1 minute set obj.ttl = 1m; } But what is the default setting (assuming the backend server is ...
Ade's user avatar
  • 709
23 votes
4 answers
18k views

How effective is LSI CacheCade SSD storage tiering?

LSI offers their CacheCade storage tiering technology, which allows SSD devices to be used as read and write caches to augment traditional RAID arrays. Other vendors have adopted similar technologies;...
ewwhite's user avatar
  • 198k
11 votes
5 answers
18k views

How do I add no-cache headers to all 404 pages served by apache and nginx?

I have recently run into an issue after switching to Cloudflare, and the solution is to basically stop Cloudflare from caching 404 responses. In our load-balanced multi-server setup, occasional 404s ...
Artem Russakovskii's user avatar
10 votes
2 answers
5k views

Caching proxy for yum and debian repositories

Does a caching proxy for yum exist, similar to approx for Debian repositories? Is there a way to have reprepro behave the same as approx? I have heard that approx was not as stable; besides, I would ...
Sushant Jain's user avatar
7 votes
2 answers
25k views

How can I cache YouTube videos with Squid Cache?

we're using the Squid cache in our company. Is there any way we can cache YouTube videos? cheers :)
Pure.Krome's user avatar
  • 6,608
7 votes
2 answers
3k views

Apache's htcacheclean doesn't scale: How to tame a huge Apache disk_cache?

We have an Apache setup with a huge disk_cache (>500.000 entries, >50 GB disk space used). The cache grows by 16 GB every day. My problem is that the cache seems to be growing nearly as fast as it's ...
flight's user avatar
  • 394
7 votes
5 answers
8k views

Free / Cached / Available memory on Linux

I have read that linux uses free memory for caching, to make system faster. However, both Nagios and Paessler PRTG monitoring system show me that my memory usage is critical. I could change Nagios ...
pkoraca's user avatar
  • 81
4 votes
2 answers
26k views

Linux cached memory: Over 85% of cached memory and using swap

I read about Linux and cachd memory at linuxatemyram but there is something that doesn't make sense to me, if the server have even a low load, instead of freeing some cached memory it starts using ...
Kuf's user avatar
  • 449
3 votes
1 answer
1k views

Why does TTL sometimes re-increment between DNS queries?

I dig xkcd.com, and I get something like this back: ; <<>> DiG 9.9.5-3ubuntu0.1-Ubuntu <<>> xkcd.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: ...
dayuloli's user avatar
  • 1,293
3 votes
2 answers
309 views

Is there an Elegant solution to rewrite long image?query-urls into cachable_nice_urls, using only apache htaccess?

this is a pain in the ass-problem! Whicever genius solves this riddle will receive paypal donation to eat diner for two. Now lets get started. Given: most proxies, do not cache resources with a "?" in ...
Sam's user avatar
  • 423
3 votes
2 answers
1k views

Unexplained cache RAM drops on Linux machine

I run a CentOS 5.7 64 machine with 24gb ram and running kernel 2.6.18-274.12.1.el5. This machine runs only Nginx, php-fpm and Xcache as extra applications. Since about 3 weeks my memory behavior on ...
Mr.Boon's user avatar
  • 1,481
2 votes
1 answer
2k views

NGINX cache (same URL) first returns MISS to all Chrome, Curl and Wget

I have a nginx cache proxy that gets content from an apache origin server. I make requests from curl, wget and Chrome to verify the cache response. Problem is that, for same URL, I always get a MISS ...
adrianTNT's user avatar
  • 1,149
2 votes
2 answers
147 views

linux caches route with IPs of machine it has no access to

I have a VPN with a gateway, and an application server. The app server only knows about the gateway of the VPN. The gateway of the VPN knows about the gateway of the physical network the vms are ...
greg0ire's user avatar
  • 316
1 vote
2 answers
1k views

running nginx as a reverse proxy with apache

Q1) Do I need mod_deflate running on apache? does it help in performance in anyway? Q2) Do I need mod_cache running on apache if nginx is serving a static caching proxy? <IfModule mod_cache.c> ...
John's user avatar
  • 53
0 votes
2 answers
8k views

How to update domain password cache over vpn

I have a machine that connects to a domain over a VPN, however it hasn't connected for months and has an old domain password (that I have forgotten) cached on it and won't let me log in to the box ...
user avatar
0 votes
2 answers
962 views

Adding location-block to cache files makes those files return 404

I want to cache some static files using Nginx. But I somehow can't get it to work. This is my nginx.conf: user www-data; worker_processes auto; pid /run/nginx.pid; include /etc/nginx/modules-enabled/*....
O'Niel's user avatar
  • 105
43 votes
6 answers
38k views

Which PHP (opcode) cache one should use and why?

I keep hearing about some PHP (opcode) caches like - APC, XCache, Memcache, eAccelerator, etc. But I couldn't ever figure out how to go about choosing one. Apart from performance benefit, which a ...
rahul286's user avatar
  • 1,657
34 votes
2 answers
41k views

No Cache-Control Header for files from AWS CloudFront with S3 Origin

We just migrated to Amazon AWS. We currently have an EC2 instance that's working well. It's running Nginx in front and Apache in the back-end. That's running well also. All sites are launched properly ...
jarvis's user avatar
  • 2,006
28 votes
4 answers
142k views

How do I disable tomcat caching? I'm having weird static file problems

How do I prevent tomcat from caching? I have css and basic html files that I load and use via ajax, and unless I restart tomcat, the changes do not seem to reflect. Different machines, different ...
Stefan Kendall's user avatar
18 votes
2 answers
41k views

Nginx not caching data

I have a REST API behind an nginx proxy. Proxying works fine, however I am unable to cache any responses. Any help would be much appreciated: Nginx config: worker_processes 10; error_log logs/...
nick_v1's user avatar
  • 365
13 votes
6 answers
45k views

sssd and ldap authentication cache

On our box running OpenSUSE 12.2 we have installed OpenLDAP and sssd daemon. We are using these two services for user authentication. Recently we created a script which creates new web-users for our ...
Seth Rayer's user avatar
13 votes
5 answers
25k views

Does it matter in which order rules are placed in htaccess?

I hope this is a simple YES or NO answer (please specify why) Q1: Does it matter in which order rules are placed in htaccess? Especially when they are completely separated items. Q2: If yes, am I ...
Sam's user avatar
  • 423
12 votes
5 answers
30k views

How to configure nginx to serve static contents from RAM?

I want to set up Nginx as my web server. I want to have image files cached in the memory (RAM) rather than disk. I am serving a small page and want a few images always served from RAM. I don't wish to ...
Vijayendra's user avatar
12 votes
5 answers
21k views

Is there a way to force windows to cache a file in RAM

I have a windows server 2008 R2 file server, that has some large files that on rare occasions is very important to get copied to another system as quickly as possible. Is there a way to force these ...
Josh's user avatar
  • 255
11 votes
2 answers
32k views

bind9 does not resolve dnssec correctly

I have a problem with my dns server setup. My bind server is mainly a cache-server but does also serve some internal domains. It listens only on my private network and serves only requests from there. ...
user avatar
11 votes
3 answers
12k views

Why does Apache send 200 OK while Last-modified matches If-modified-since?

I'm trying to have a basic behavior regarding my caching strategy: files should be cached, and revalidated with server each time. So I would like Apache to send a 304 back. Here is the dialog that ...
zrz's user avatar
  • 253
11 votes
1 answer
19k views

How to add response headers with HAproxy 1.6 based on request URI?

I use HAproxy 1.6 as load balancer in front of tomcat servers. I need to add response headers based on the request URI. For e.g., I'd like to add the response header Cache-Control public,max-age="...
jmlrt's user avatar
  • 113
9 votes
4 answers
12k views

Cloudflare not caching static files as expected (cf-cache-status: MISS)

I'm wondering why Cloulflare would not cache a certain static js file. Given the reuqest: curl -I http://www.testlifeinuk.com/dist/lifeinuk.js the headers returned like: HTTP/1.1 200 OK Date: Mon, ...
Wudong's user avatar
  • 201
9 votes
5 answers
6k views

Squid or Other HTTP Caches with SSD Cache Store?

I'm contemplating setting up a squid (or possibly varnish) cache on a system with SSD drives. The obvious benefit is that these systems have great READ speeds and I expect my hit ratios to be fairly ...
Joel K's user avatar
  • 5,903
8 votes
2 answers
19k views

Setting up a reverse proxy to cache images

I wrote a quick Python server to serve resampled images. For example, a URL might look something like http://images.domain.com/resample/100x100/9f362e1994264321.jpg. Being that resampling images is ...
Theron Luhn's user avatar
7 votes
1 answer
6k views

Working Nginx fastcgi_cache php-fpm cache and static file caching configuration?

Nginx wiki is very vague with explanation as to how to properly setup nginx with php-fpm with fastcgi_caching for sites which have cookies i.e. wordpress, drupal, vbulletin etc. I downloaded a ...
p4guru's user avatar
  • 963
6 votes
2 answers
8k views

How to make Varnish ignore, not delete cookies

I want to use Varnish to cache certain pages even in the presence of cookies. There are 3 possibilities that I need to take care of: An anonymous user is viewing some page A logged in user is viewing ...
Jason Christa's user avatar
6 votes
4 answers
8k views

ZFS - enable or disable disk cache?

I'm setting up ZFS (through FreeNAS) with RAIDZ1 on a server with 4 x WD Red SATA HDDs (connected through a PERC H330 in HBA mode). The server is hooked to a UPS. For ZFS and in this setup, does it ...
matthias_buehlmann's user avatar
6 votes
4 answers
12k views

Caching OpenLDAP credentials for offline use on laptops

Our clients (Ubuntu 14.04) can login with there LDAP login. As soon as they have no network they cannot login with LDAP. Is there a way to cache those passwords and usernames, so that the laptops ...
Joeri Feyen's user avatar
6 votes
3 answers
6k views

Making SATA disk write cache safe

Supposedly (see, e.g., a question about it here), with NCQ enabled drives, the drive write cache is supposed to be safe, as in it doesn't lie to the OS about data being committed to the platters when ...
derobert's user avatar
  • 1,318
6 votes
2 answers
6k views

What is the difference between proxy_cache_ and fastcgi_cache?

I was searching for a simple Nginx microcache solution and I end up seeing two ways to have microcache. Some tutorials use proxy_cache, while others fastcgi_cache. What are the differences, pros and ...
Daniel's user avatar
  • 193
5 votes
1 answer
3k views

Why is the ssl session cache ( ssl_session_cache) disabled by default in nginx?

In nginx, the ssl_session_cache directive has a default of 'none'. ref However, in the documentation for configuring HTTPS server, it's advised to turn on the ssl session cache, as it explains that ...
CausingUnderflowsEverywhere's user avatar