Questions tagged [cache]
A location or process for storing of transitory or temporary data in order to improve application or system performance.
1,602
questions
122
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8
answers
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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 ...
- 1,320
100
votes
18
answers
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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 ...
- 2,730
96
votes
5
answers
112k
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 ...
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93
votes
16
answers
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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 ...
- 1,072
46
votes
4
answers
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How do I remove a specific bad plan from the SQL Server query cache?
We have one particular SQL Server 2008 query (not a stored proc, but the same SQL string -- executes every 5 minutes) that intermittently caches a very bad query plan.
This query normally runs in a ...
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43
votes
6
answers
38k
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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 ...
- 1,667
34
votes
2
answers
42k
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 ...
- 2,006
31
votes
7
answers
154k
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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 ...
- 788
31
votes
3
answers
15k
views
What effect does https traffic have on web cache proxy servers?
I just took two university courses on computer security and internet programming. I was thinking about this the other day:
Web cache proxy servers cache popular content from servers on the web. This ...
- 413
28
votes
4
answers
143k
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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 ...
- 1,079
26
votes
5
answers
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Does CURL cache requests?
This is a pretty long question, so bear with me.
I wanted to stress my Akamai Server logged in from an AWS instance. So, I started running ab benchmark. However, they seemed ridiculously fast to ...
26
votes
2
answers
21k
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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-...
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25
votes
2
answers
36k
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 ...
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25
votes
2
answers
33k
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For L2ARC and ZIL: is it better to have one large SSD for both, or two smaller SSDs?
Main references
ZFS L2ARC (Brendan Gregg) (2008-07-22) and ZFS and the Hybrid Storage Concept (Anatol Studler's Blog) (2008-11-11) include the following diagram:
Question
Should I interpret the ...
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24
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;...
- 199k
23
votes
3
answers
36k
views
When to use or not to use sendfile on/off in Nginx?
We have this setting in our nginx.conf for quite a while.
sendfile on;
When we have updated a file e.g. /js/main.js and access from browser https://test.com/js/main.js?newrandomtimestamp, it will ...
- 965
22
votes
2
answers
9k
views
What is the latency WITHIN a data center? I ask this assuming there are orders of magnitude of difference
I am trying to figure out something that I just cannot find a good answer to.
If I have say a REDIS cache (or some external in-memory cache) sitting in a data center, and an application server ...
- 353
21
votes
5
answers
16k
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?
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20
votes
2
answers
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Nginx caching symlinks
I have a deployment system on my web server, every time an app is deployed it creates a new timestamped directory and symlinks "current" to the new directory. This all workded good and great on apache,...
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20
votes
4
answers
15k
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Does a RAID controller with an NV cache improve the performance or integrity of an SSD array?
I am planning to purchase a server (Dell PowerEdge R740) with SSDs in RAID 10, and my priorities are write performance and data integrity. It will be running Linux. The SSDs have write caches with ...
- 499
18
votes
2
answers
41k
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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/...
- 365
17
votes
5
answers
106k
views
How can I clear the "authentication cache" in Windows 7 to a password protected samba share?
I have a Linux samba server and have explicitly listed users that can access the folder.
I have successfully congfigured Samba to require a username and password when accessing the share from windows ...
- 315
17
votes
1
answer
7k
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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 ...
- 2,975
17
votes
2
answers
12k
views
Main differences between SSI (Server Side Include) and ESI (Edge Side include)
I need to include dynamic content into static pages at web server level. The 2 options I have found so far are Server Side Include (SSI) and Edge Side Include (ESI).
While the origins of SSI seem ...
- 3,583
15
votes
6
answers
88k
views
Does my ISP cache the DNS?
I went to my zoneedit.com, changed mydomain.com to point to a different IP.
But changes haven't taken affect yet.
Is this because my ISP DNS is caching?
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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.
...
- 268
15
votes
4
answers
44k
views
How to clear (remove/delete) certificate (ssl/https) cache from chrome browser?
I lost many hours while setting up some self-signed certificates; the problem turned out to be that the browser (Chrome) cached a bad version of the certificate and then just wouldn't let go. I did ...
- 271
14
votes
7
answers
9k
views
SQL Server - Force DB in memory?
We have a beefy Windows 2008 x64 server (4 x 4 core CPU, 32GB RAM) running SQL Server 2005 64-bit. We have a small (6GB) but very important database that is somewhat slow to access until the pages are ...
- 1,502
14
votes
3
answers
35k
views
Hardware RAID controller cache battery failure frequency/lifetime?
I'm in an environment that contains many Supermicro servers equipped with Adaptec and LSI MegaRAID hardware RAID controllers. These controllers contain battery-backed cache modules to help boost write ...
- 199k
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 ...
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13
votes
2
answers
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views
Purge varnish cache for a single url using varnishadm
Varnish is being used in a Wordpress website.
I would like to purge Varnish for a single URL instead of a whole domain.
With this command I can restart Varnish for the whole domain:
varnishadm -T :...
- 201
13
votes
6
answers
46k
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 ...
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13
votes
5
answers
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views
How to solve "ExpiresActive not allowed here" error message in .htaccess file?
I am trying to add Expires headers to the HTTP responses of the site I am working on. The only way for me to control the Apache 1.3 server is by editing my .htaccess file. I tried adding code such as ...
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13
votes
1
answer
14k
views
Managing battery relearn cycles on LSI and similar RAID controllers
How do engineers deal with RAID controller battery "relearn" cycles?
As noted in: What's a "battery relearn" on a LSI MegaRaid?, relearn cycle discharges the RAID controller battery (...
- 199k
13
votes
3
answers
13k
views
Tuning Linux disk caching behaviour for maximum throughput
I'm running into a maximum throughput issue here and need some advice on which way to tune my knobs. We're running a 10Gbit fileserver for backup distribution. It's a two disk S-ATA2 setup on an LSI ...
- 450
13
votes
2
answers
17k
views
Linux; What is stripe_cache_size and what does it do?
I am currently building a software RAID under Linux using mdadm utility and I've read a few articles that describe how to increase the stripe_cache_size value for that RAID and how to calculate an ...
- 4,272
12
votes
2
answers
5k
views
Windows Server 2008 R2 64-bit memory leak
I´m having trouble in one of my office servers. It´s a virtualized Windows 2008 R2 Server with 6GB RAM memory. It only has Microsoft SQL Server (memory assigned maximum = 3GB), and just a software ...
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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 ...
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12
votes
2
answers
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views
Tomcat 8 org.apache.catalina.webresources.Cache.getResource
I have just upgraded from 7.0.52 to 8.0.14.
I am getting this for lots of static image files:
org.apache.catalina.webresources.Cache.getResource Unable to add the
resource at [/base/1325/WA6144-...
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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 ...
- 255
12
votes
4
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 ...
- 263
12
votes
5
answers
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views
How to load-balance SQL Server 2008 for high-usage ASP.NET applications?
Imagine that you have a successful web application that uses ASP.NET and IIS 7. It generates many calls to a SQL Server 2008 database, and is expected to be available to the public with 99.9% uptime (...
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11
votes
2
answers
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views
ZFS and cache devices
I'm going to add a SSD drives to my ZFS storages as a cache. Anyone has any experience with this? What if cache device dies, will the any data be affected?
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11
votes
5
answers
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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 ...
- 1,003
11
votes
3
answers
33k
views
Will an IIS reset force cached items to be resent?
I'm trying to develop a strategy to handle cached javascript files, css, images, etc when we release an update to our site. Before I get into implementing version numbers on the javascript files I was ...
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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="...
- 113
11
votes
2
answers
33k
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.
...
user364476
11
votes
2
answers
8k
views
nginx use proxy cache if backend is down
I need to nginx proxy use cache if backend server down:
this is my configuration. but seems be nginx use cache without check backend server.
http {
# ...
proxy_set_header Host $host;
...
11
votes
2
answers
11k
views
How to Create Yum Cache Server for client machines in LAN
Like in Ubuntu we have the option of creating "Ubuntu update cache server" which downloads and update packages directly from internet and serves other client ubuntu machines for installing/updating ...
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11
votes
3
answers
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views
Irregular internet disruption: certain images and JS not loading
first time on ServerFault, and I've got a nice little conundrum.
Since a few months now, we've been having issues with our internet connectivity.
Environment:
Servers: 2 Terminal Servers as an ...
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