How to unmount NFS share mounted with hard option
29 Aug2007

Few days ago I worked on some customer’s server and there was a problem – their nfs server went down and we were forced to change some settings on their FC4 clients to prevent shares from dieing because of kernel bug. But when we’ve changed settings in /etc/fstab there was one more step before task was completed – we need to remount this share (I mean unmount/mount). But how to perform this operation if there are some processes in D (non-interruptible sleep) waiting for dead share and prevent it from unmounting? They wait because of hard option on the share and lack of intr option and any unmount request would produce a following results:

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streaming01:~# umount /storages/2
umount: /storages/2: device is busy
umount: /storages/2: device is busy

So, here is a list of steps you need to do to be able to remount your share.

First of all, you need to send KILL(9) signal to all you processes waiting for share. I’ve used ps axu and filtered all processes in D state. When all processes ‘killed’ (they can’t be killed actually), you’ll need to send the same signal to rpciod processes in your system. After this all your sleeping processes will die and you’ll be able to unmount your share.

That’s it – simple and really useful tip for people using NFS in their systems.


1000 Great Technical Videos in BestTechVideos Library!
11 Aug2007

Yes! We did it! Just before I went to bed at 3:40AM (heh :) ), I noticed, that someone submitted new video to BTV. I’ve approved it instantly and then noticed a following information in the top part of the site: “We have 1000 videos / 569+ hours of high-quality content!” So, we broke trough 1k videos barrier! And we’ll try to do 2k videos before the end of this year, we have some new features in closed beta testing which would greatly increase number of submitted videos each day.

Thanks to all our users for their contributions and support! Stay with us and we’ll try to give you more features really soon.


Using Nginx, SSI and Memcache to Make Your Web Applications Faster
5 Aug2007

If you’d take a look at any web site, you will notice, that almost all of the pages on this given site are pretty static in their nature. Or course, this site could have some dynamic elements like login field or link in the header, some customized menu elements and some other things… But entire page could be considered static in many cases.

When I started thinking about my sites from this point of view, I understood, how great it would be to be able to cache entire page somewhere (in memcache for example) and be able to send it to the user without any requests to my applications, which are pretty slow (comparing to memcache ;-) ) in content generation. Then I came up with a pretty simple and really powerful idea I’ll describe in this article. An idea of caching entire pages of the site and using my application only to generate small partials of the page. This idea allows me to handle hundreds of queries with one server running pretty slow (yeah! it is slow even after all optimizations on MySQL side and lots of tweaks in site’s code) Ruby on Rails application. Of course, the idea is kind of universal and could be used with any back-end languages, technologies or frameworks because all of them are slower then memcache in content “generation”.

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