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

learn more… | top users | synonyms (1)

55
votes
11answers
12k 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. ...
2
votes
2answers
4k 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 ...
3
votes
3answers
3k 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.
13
votes
1answer
5k 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 ...
27
votes
17answers
26k 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 ...
15
votes
3answers
7k 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?
13
votes
6answers
8k 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. ...
42
votes
3answers
30k 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 ...
17
votes
3answers
5k 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 ...
12
votes
2answers
11k 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 ...
5
votes
2answers
2k 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 ...
6
votes
2answers
12k 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 :)
3
votes
4answers
7k 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 then disk. I am serving a small page and want few images always served from RAM. I dont wish to ...
6
votes
5answers
3k 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 ...
3
votes
2answers
255 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 ...
2
votes
2answers
102 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 ...
1
vote
2answers
997 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> ...
0
votes
1answer
925 views

APC File Cache not working but user cache is fine [closed]

I have just got a VPS (with cPanel/WHM) to test what gains i could get in my application with using apc file cache AND user cache. So firstly I got the PHP 5.3 compiled in as a DSO (apache module). ...
3
votes
1answer
90 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: ...
3
votes
2answers
984 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 ...
0
votes
2answers
4k 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 ...
31
votes
5answers
24k 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 ...
31
votes
5answers
39k views

Setting expires headers for static content served from nginx

I'm using nginx to server my static content, is there a way that I can set the expires headers for every file that meets a specific rule? For example can I set the expires header for all files that ...
14
votes
1answer
6k 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 ...
7
votes
5answers
5k 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 ...
4
votes
3answers
159 views

What's a good resource for learning about scaling PHP applications?

I know PHP fairly well. But one aspect of PHP which I am fairly green in is caching, loading balancing etc. A lot of companies hiring PHP developers are looking for these high-use background, which ...
8
votes
1answer
1k views

Vagrant NFS share doesn't show updated file if size doesn't change

When mounting /vagrant over NFS, a changed file on the host is not refresh on the guest if the size doesn't changes. Quick update/typo are not immediately reflected unless I make enough modification ...
6
votes
1answer
4k 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 ...
2
votes
2answers
1k views

Unusual Apache->Tomcat caching issue

Right now, I have an Apache setup sitting in front of Tomcat to handle caching. This setup has been given to an external service to manage, and since the transition, I've noticed odd behavior. ...
1
vote
2answers
357 views

Selectively clearning cache/buffers

Is it possible to selectively clear content from a particular filesystem, or file/directory within a filesystem, under Linux. This can be done globally with sync; echo 3 > /proc/sys/vm/drop_caches ...
10
votes
2answers
42k views

Clearning Chrome 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 ...
3
votes
1answer
334 views

My server doesn't seem to be caching anything well

I have a VPS from tocici (via BuildYourVPS). It's got 4 GB of RAM (2 GB of it "burst" RAM). This server has some severe performance issues, however. First, a quick explanation of what this server ...
3
votes
2answers
2k views

Does is matter in what order rules are placed in htaccess?

I hope this is a simple YES or NO answer (please specify why) Q1: Does is matter in what order the rules are placed in htaccess? Since they are completely separated items: for example Q2: If yes, am ...
3
votes
1answer
4k views

ASP.NET cache trimming aware of app pool memory limit?

I’m running a ASP.NET application on Win2003 32bit that tends to allocate a lot of memory. To avoid OutOfMemoryExceptions that start to appear when the W3P process exceeds 1 GB, I have set a maximum ...
3
votes
2answers
5k views

Apache redirect and set cache headers?

Doing a redirect in Apache is easy (mod_alias): RedirectMatch ^.*$ http://portal.example.com/ Setting cache headers is equally easy: Header set Cache-Control max-age=0 Header set Expires "Thu, 01 ...
2
votes
4answers
3k 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 ...
1
vote
3answers
522 views

Can APC recognise duplicate source files?

I have a webserver with lots of sites which are all based on Drupal. The sites share a vast majority of identical code, and it'd be great if APC could take advantage of this and not 're-cache' the ...
0
votes
1answer
200 views

url rewrite to make generated thumnails cache like static, a syntax question

this is a pain in the ass-problem!! Given: most proxies, do not cache resources with a "?" in their URL even if a Cache-control: public header is present in the response. To enable proxy caching for ...
5
votes
3answers
4k 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 like to the OS about data being committed to the platters when ...
4
votes
1answer
204 views

Is this a case of a stale ISP DNS cache or did I fudge something up?

I am currently in the process of transferring a legacy website (from a legacy hosting service provider) to a modern solution. Due to my context-specific requirements (which include financial ...
4
votes
3answers
2k views

Varnish only cache assets from single session

Currently I manage to configure varnish to cache items from 1 user, but the when the second users comes in varnish fetch another asset from Apache. How can I cache static assets behind magento ( ...
2
votes
1answer
2k views

Setting Up Apache as a Forward Proxy with Caching

I am trying to set up Apache as a forward proxy with caching, but it does not seem to be working correctly. Getting Apache working as a forward proxy was no problem, but no matter what I do it is not ...
2
votes
4answers
124 views

Is this a good behaviour? [duplicate]

My centos 5.7 is running Magento. 4GB RAM and 4 Cores. Nginx + spwan-fcgi + memcached (Best performance if you ask me). Now i'm a little bit concerned about the Memory usage. [root@adikastyle ...
2
votes
2answers
3k views

Avoiding Varnish Hitting Magento Cookies - VCL

Hello to serverfault users, I would like to kindly ask someone to help me configure varnish for magento. Using command: varnishtop -i TxHeader -I Cookie , following info show: TxHeader Cookie: ...
2
votes
5answers
3k views

Downloads pause and time out frequently

I'm a new systems and network admin. My experience has been in the hardware and software of systems and servers, the network part is pretty new to me. I'm familiar with plugging numbers into network ...
2
votes
2answers
493 views

Purging AD Principal from cache

A user in the Active Directory has had a change of his SAM account name, but a web application running IIS still recognizes him under his old SAM Account name. I presume this is because the AD ...
2
votes
5answers
4k views

Why does APC (or similar) cause performance problem for shared hosting?

I'm using shared hosting, and I can't enable APC. There was a thread about that here, and the only reason suggested was for security (php-cgi vs mod_php). I queried the host, and they said it was due ...
2
votes
2answers
5k views

How to make HTTP Cache Headers Work

Can someone please help me with a HTTP caching question? I thought that if I set the "Expires" and "Cache-Control:max-age" request headers, then a browser wouldn't make a GET request until after the ...
1
vote
0answers
19 views

Keep file system meta data in cache with vfs_cache_pressure

My Ubuntu Linux (virtual) servers run rdiff-backup daily, which looks at all file meta data to determine what needs to be backed up, slowing it down. It does this every day, even though most files ...
1
vote
0answers
178 views

LSA SID cache keeps old entry for renamed domain user - why?

I have a question about LSA SID cache on a domain member server. Recently I run into the issue when some users after their name was changed in AD has difficulties accessing application I support, and ...