Ask MetaFilter questions tagged with caching

How does windows do filesystem caching?

torpark — Wed, 18 Mar 2009 18:23:41 -0800

How does windows do filesystem caching? When I mount NTFS via linux, the performance is much slower than when i used window. How does windows handle the filesystem caching? I am not talking about file indexing/searching, but read/write performance. Is it a service? A method?

Page view limit exceeded why?

invitapriore — Mon, 21 Apr 2008 00:05:39 -0800

This page (a website for public domain scores) tells me that my daily allotment of download page visits (2 per day per IP, I imagine) has been exceeded the first time I go to one of those pages. I'm using Firefox 2.0.0.14 on OS X 10.5.1. I mostly want to know if it is browser behavior, such as pre-caching of pages. I don't think any other problem is within my power to resolve.

An additional note is that this page has worked for me before, but not for about a week. I'm not sure if this coincides with an update or not.

How do I force Firefox to cache PNG files?

Doofus Magoo — Wed, 12 Mar 2008 12:03:29 -0800

How do I force Firefox to cache PNGs? So there's a website that I visit from which I was recently blocked due to excessive hits against the server (something painful like 90+ hits per minute over 30+ minutes). I checked with the site administrators, and after going through their server logs, they reported there were a "lot of PNG files being opened over and over again," and that they (PNGs) probably weren't being cached properly.

Further they told me that:

In Firefox, the default action for PNG files is to open them using QuickTime instead of SaveToDisk. You will need to change the default action to SaveToDisk as there were a lot of files with PNG extensions in your log file. They may not have been cached properly which could have caused all the hits against our site because Quicktime was intercepting the default action.

This seems a little hand-wavey to me -- I guarantee I'm not the only person using Firefox on this site, and to complicate things a bit further, I don't even have QuickTime installed on this computer.

Can anyone else think of anything that would cause my computer to not cache PNG files correctly? I'm using Firefox 2.0.0.12 on Windows XP SP2, and don't have any extensions installed that aren't too off the wall (AdBlock Plus, NoScript, del.icio.us, Firebug, Google Browser Sync, Sage, Web Developer, ChatZilla).

Cashy My Apache

jasondigitized — Wed, 18 Jul 2007 17:49:24 -0800

I am attempting to configure caching on an Apache server. I have it right for the most part, but.....I would like to prevent browsers from even checking the server once files like images are in the browser cache until an expiry date is exceeded. As an example, I am placing this in my httpd.conf file:

Header add "Expires" "Mon, 28 Jul 2014 23:30:00 GMT"
Header add "Cache-Control" "max-age=31536000"

mod_expires and mod_headers are turned on. According to Firebug, all of my images are 'caching', but my browser is still checking the server, and is receiving a '304 Not Modified' message. The is good, but not good enough. How can I prevent the browser from checking the server. Once that image is in the cache, I don't want my browser checking the server until after the expiry or max-age is exceeded. Is this possible? According to this article, "You can prevent the contact with the server from happening at all by using the Expires header and the Cache-control header."

Why do I still see our old website even though the DNS should have had plenty of time to propagate?

bcwinters — Sat, 03 Feb 2007 10:03:21 -0800

DNS and Small Business Server and Caches, oh my: We switched web hosts at work (and waited a few days for things to propagate), but from the office network I still see the site on the old host. Can anyone help me understand DNS caching, Active Directory, and all the other bits and bobs that go along with the mysterious world of Windows networks? I work for a nonprofit. We don't have an IT guy; just me, a talentedish amateur who's now trying to troubleshoot DNS caching. I am the quote-unquote administrator of the network, which means I know how to add users to Active Directory, restart the server when it's acting flakey, and Google the right search terms when things go awry.

We switched web hosts on Monday night and a rudimentary check tells me that the DNS changes propagated all over creation within a day or three. But when I'm at work, I still see the old site no matter how many times I flush browser caches or DNS caches on our workstations. I've tried multiple browsers and even brought in a laptop that has never been on the network before, just to make sure it wasn't a problem with the workstations caching something.

Having ruled that out, I checked our router, a Sonicwall TZ 170. I'm normally pretty confident with routers (I always seem to be the friend who gets the phone calls in the middle of the night when somebody's net connection has crapped out) although I don't know much about the setup of our VPN, etc. I noticed that the first DNS server was set to point internally to our server (192.168.1.2), which seemed odd to me. The other two DNS servers were 4.2.2.2 and 4.2.2.1, which seemed normal enough.

Some Googling turned up this tangentially-related question, where a commenter noted that "All DC's should have the primary DNS entry pointing to themselves. A lot of the functionality of Active Directory is based on DNS..." so I figured, OK, it's not an error, let me take a look at the server.

At this point my knowledge peters out. We use Small Business Server 2003, and I got as far as looking at the properties of the server in dnsmgmt. "Interfaces" is set to "Only the following IP addresses: 192.168.1.2"; Forwarders is set to "All other DNS domains" and 4.2.2.2 & 192.168.1.1. I don't really understand why it would be set to try an outside nameserver and then try the router second; wouldn't the router just tell it to circle back around to the server? Does this even have anything to do with anything??

Sorry if this is very wordy. I wanted to try and cover all the bases and show y'all what I've tried (as well as expose how rudimentary my actually skills are on the topic!). One last thing; I've got a text file of some tracert results from my laptop that's connected to the office network via the VPN:

1 1 ms 1 ms 1 ms c-24-62-154-34.hsd1.nh.comcast.net [24.62.154.34]
2 26 ms 21 ms 7 ms c-3-0-ubr01.concord.nh.boston.comcast.net [73.165.206.1]
3 10 ms 9 ms 13 ms ge-2-37-ur01.concord.nh.boston.comcast.net [68.87.148.193]
4 10 ms 10 ms 10 ms 10g-8-1-ur01.deering.nh.boston.comcast.net [68.87.145.69]
5 10 ms 23 ms 10 ms 10g-9-4-ur01.manchester.nh.boston.comcast.net [68.87.145.81]
6 11 ms 11 ms 13 ms 10g-9-1-ur01.nashua.nh.boston.comcast.net [68.87.145.117]
7 10 ms 14 ms 11 ms te-9-2-ur01.lowell.ma.boston.comcast.net [68.87.144.161]
8 10 ms 12 ms 11 ms 10g-9-4-ar01.needham.ma.boston.comcast.net [68.87.144.157]
9 12 ms 12 ms 14 ms 12.116.130.173
10 20 ms 25 ms 22 ms br2-a350s3.cb1ma.ip.att.net [12.127.5.26]
11 23 ms 19 ms 19 ms tbr2-cl16.n54ny.ip.att.net [12.122.10.22]
12 19 ms 17 ms 19 ms ggr1-p320.n54ny.ip.att.net [12.123.0.85]
13 20 ms 18 ms 20 ms p14-0.ir1.nyc-ny.us.xo.net [206.111.13.33]
14 19 ms 20 ms 19 ms p5-0-0.RAR2.NYC-NY.us.xo.net [65.106.3.41]
15 25 ms 23 ms 26 ms p6-0-0.RAR1.Washington-DC.us.xo.net [65.106.0.2]
16 92 ms 93 ms 106 ms p1-0-0.RAR1.SanJose-CA.us.xo.net [65.106.0.38]
17 91 ms 91 ms 93 ms p0-0-0d0.RAR2.SanJose-CA.us.xo.net [65.106.1.62]
18 96 ms 94 ms 94 ms p15-0.DCR1.DC-Fremont-CA.us.xo.net [65.106.2.154]
19 123 ms 99 ms 94 ms 205.158.60.166.ptr.us.xo.net [205.158.60.166]
20 91 ms 91 ms 95 ms dsr1.dc-fremont-ca.us.xo.net [205.158.60.229]
21 leander.cnchost.com [207.155.252.112] reports: Destination net unreachable.

Trace complete.

Anyway, that's all I've got. Any advice appreciated. I understand that DNS changes take a while to propagate, but five days seems a bit excessive--plus I'll probably be in trouble at work on Monday if the bosses are still seeing our old website!

As a final add-on to my question: anybody got any advice on good books/resources to learn about the workings of Small Business Server, Active Directory and the merry world of Windows networking that are good for laypeople who need to do more than have their hands held while using a Wizard?

Coral Cache: What's the Catch?

baylink — Sat, 29 Jul 2006 09:48:33 -0800

What's the catch with Coral Cache? Is there... Why yes, there is; thanks for asking. :-)

I've seen several people recommend Coral Cache to other people in various AskMe threads, including one today. It seems like it has no visible means of support. It is just a research project, paid for by New Yorkers' tax dollars? Is it going to Google/Yahoo out and end up going commercial? Who is that Man behind that Curtain? And what about Naomi?

A couple of specific questions: how does it interact with dynamic sites? Does their caching engine rewrite *all* links it finds in pages to the same site to push them to the cache? Can you override it? Should I have read every page on their site to find these answers instead? :-)

Most importantly, in an AskMe State Of Mind: has anyone here used it extensively, and what did you think?

How can I keep my plaintext data from leaking?

phrontist — Mon, 17 Oct 2005 18:34:47 -0800

I'm writing some personal wiki software that I want to make as secure as possible. Think wiki software in the footsteps of Tinfoil Hat Linux. The software is intended to run as a CGI Perl script though Apache on the local machine, with data stored in encrypted XML files that will be decrypted for display by the Crypt::GPG module. So the question is, where could plaintext data escape to? More inside... The most obvious is the browser (which, in my usage, would be Firefox on Debian), but I've ascertained that one can prevent Mozilla and most other browsers from caching data by using HTTPS. What about Apache itself? Does apache cache data by defualt in any way (other than access logs)? Is there something I'm not thinking of?

A bit paranoid? Maybe, but I do intend to commit every facet of my life to this thing, so a little parnoia is warranted.

Web browser with permanent cache?

calwatch — Wed, 25 Aug 2004 22:26:45 -0800

Is there a web browser that has a permanent cache? Basically, I'm looking for something that acts like a normal interactive browser (not wget or something similar) but with a feature that saves the page just viewed. It would be handy for forensic Internet sleuthing, as well as general "where did I see this" questions. Kind of like the history but with actual pages attached to it. Also with hard drive prices dropping like a rock space shouldn't be a problem.

Does such a thing exist?

Strange problems with IP / DNS caching

twine42 — Sat, 03 Jul 2004 07:25:45 -0800

Strange problems with IP / DNS caching (maybe) {more inside} This is odd. We have two computers which I'll call the server and the desktop. Server does nothing but run the adsl and store files.

One website my wife uses moved servers recently. Since then she's been getting the old site while the server can view the new site.

I ran tracert on both and found that the two machines are calling different IP addresses, so I've changed her hosts to bounce her to the new IP, but this feels hacky and short term. What's happened and how do I fix it?

both PCs are Win XP Pro, running Firefox and IE 6.