Linux: Should You Use Twice the Amount of Ram as Swap Space?

Posted on in Categories data center, Debian Linux, fedora linux, File system, FreeBSD, Gentoo Linux, kernel, Linux, Linux desktop, Linux laptop, OpenBSD, RedHat/Fedora Linux, Solaris, Storage, Suse Linux, Tuning, Ubuntu Linux, UNIX last updated November 19, 2008

Linux and other Unix-like operating systems use the term “swap” to describe both the act of moving memory pages between RAM and disk, and the region of a disk the pages are stored on. It is common to use a whole partition of a hard disk for swapping. However, with the 2.6 Linux kernel, swap files are just as fast as swap partitions. Now, many admins (both Windows and Linux/UNIX) follow an old rule of thumb that your swap partition should be twice the size of your main system RAM. Let us say I’ve 32GB RAM, should I set swap space to 64 GB? Is 64 GB of swap space really required? How big should your Linux / UNIX swap space be?

Record Labels To Sue SourceForge Open Source Project Hosting Platform

Posted on in Categories GNU/Open source, Linux, Networking, News last updated November 16, 2008

Consider this … the stupidest example of law. From the blog post:

French record labels have received the green light to sue four US-based companies that develop P2P applications, including the BitTorrent client Vuze, Limewire and Morpheus. Shareaza is the fourth application, for which the labels are going after the open source development platform SourceForge.

Seagate Barracuda: 1.5TB Hard Drive Launched

Posted on in Categories Business, data center, Data recovery, File system, Hardware, Linux, Linux desktop, Storage, Sys admin, UNIX last updated October 21, 2008

Wow, this is a large size desktop hard disk for storing movies, tv shows, music / mp3s, and photos. You can also load multiple operating systems using vmware or other software for testing purpose. This hard disk comes with 5 year warranty and can transfer at 300MB/s. But, How reliable is the 1.5TB hard disk?

How To Avoid Sudden Outburst Of Backup Shell Script or Program Disk I/O on Linux

Posted on in Categories High performance computing, kernel, Linux, Storage, Troubleshooting, Tuning last updated June 3, 2008

A sudden outburst of violent disk I/O activity can bring down your email or web server. Usually, a web, mysql, or mail server serving millions and millions pages (requests) per months are prone to this kind of problem. Backup activity can increase current system load too. To avoid this kind of sudden outburst problem, run your script with scheduling class and priority. Linux comes with various utilities to manage this kind of madness.

Linux Disk Benchmarking – IO Performance With fio Tool

Posted on in Categories Hardware, Linux last updated April 9, 2008

You can use old good hdparm to find out how fast is your hard disk under Linux. There is another tool called Bonnie++ which is a benchmark suite that is aimed at performing a number of simple tests of hard drive and file system performance. Then you can decide which test is important and decide how to compare different systems after running it.

Linux.com has published article about a new tool called fio:

fio was created to allow benchmarking specific disk IO workloads. It can issue its IO requests using one of many synchronous and asynchronous IO APIs, and can also use various APIs which allow many IO requests to be issued with a single API call. You can also tune how large the files fio uses are, at what offsets in those files IO is to happen at, how much delay if any there is between issuing IO requests, and what if any filesystem sync calls are issued between each IO request. A sync call tells the operating system to make sure that any information that is cached in memory has been saved to disk and can thus introduce a significant delay. The options to fio allow you to issue very precisely defined IO patterns and see how long it takes your disk subsystem to complete these tasks.

=> Inspecting disk IO performance with fio

Linux Ramback: Use a Terabyte of RAM

Posted on in Categories Hardware, Linux last updated March 24, 2008

An experimental new design for Linux’s virtual memory system would turn a large amount of system RAM into a fast RAM disk with automatic sync to magnetic media. Most servers comes with 2-16 GB ram installed but not with a terabyte of installed memory (for 1TB+ ram go with IBM / Sun E25k server line). There is a new kernel patch called Ramback:

Ramback is a new virtual device with the ability to back a ramdisk by a real disk, obtaining the performance level of a ramdisk but with the data durability of a hard disk. To work this magic, ramback needs a little help from a UPS. In a typical test, ramback reduced a 25 second file operation to under one second including sync. Even greater gains are possible for seek-intensive applications. The difference between ramback and an ordinary ramdisk is: when the machine powers down the data does not vanish because it is continuously saved to backing store. When line power returns, the backing store repopulates the ramdisk while allowing application io to proceed concurrently. Once fully populated, a little green light winks on and file operations once again run at ramdisk speed.

However, this solution depends upon UPS:

If line power goes out while ramback is running, the UPS kicks in and a power management script switches the driver from writeback to writethrough mode. Ramback proceeds to save all remaining dirty data while forcing each new application write through to backing store immediately.

How to: Upgrade Fedora Linux From 32-bit System to 64-bit Version w/o Reinstalling Server

Posted on in Categories Howto, Links, Linux, RedHat/Fedora Linux, Tips last updated January 13, 2008

This small guide may come handy…

From the article:

One great thing about Linux is that you can transplant a hard disk from a machine that runs a 32-bit AMD XP processor into a new 64-bit Intel Core 2 machine, and the Linux installation will continue to work. However, if you do this, you’ll be running a 32-bit kernel, a C library, and a complete system install on a processor that could happily run 64-bit code. You’ll waste even more resources if your new machine has 4GB or more of system memory, and you’ll be forced to either not use some of it or run a 32-bit Physical Address Extension (PAE) kernel. Cross-grading to the 64-bit variant of your Linux distribution can help you use your resources more wisely. A disclaimer: changing the architecture of your Fedora installation from 32 to 64-bit isn’t recommended or supported in any way. Perform this at your own risk after creating a suitable backup.

=> Upgrade from 32-bit to 64-bit Fedora Linux without a system reinstall [linux.com]