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 June 8, 2017

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 required? How big should your Linux / UNIX swap space be?

mount forcedirectio: Disable Linux CIFS / NFS Client Caching

Posted on in Categories CentOS, File system, GNU/Open source, kernel, Linux, Linux Scalability, RedHat/Fedora Linux, Storage, UNIX last updated November 16, 2008

If your network is heavily loaded you may see some problem with Common Internet File System (CIFS) and NFS under Linux. By default Linux CIFS mount command will try to cache files open by the client. You can use mount option forcedirectio when mounting the CIFS filesystem to disable caching on the CIFS client. This is tested with NETAPP and other storage devices and Novell, CentOS, UNIX and Red Hat Linux systems. This is the only way to avoid data mis-compare and problems.

Linux tgtadm: Setup iSCSI Target ( SAN )

Posted on in Categories CentOS, data center, Debian Linux, fedora linux, File system, GNU/Open source, Hardware, Linux, Storage last updated November 11, 2008

Linux target framework (tgt) aims to simplify various SCSI target driver (iSCSI, Fibre Channel, SRP, etc) creation and maintenance. The key goals are the clean integration into the scsi-mid layer and implementing a great portion of tgt in user space.

The developer of IET is also helping to develop Linux SCSI target framework (stgt) which looks like it might lead to an iSCSI target implementation with an upstream kernel component. iSCSI Target can be useful:

a] To setup stateless server / client (used in diskless setups).
b] Share disks and tape drives with remote client over LAN, Wan or the Internet.
c] Setup SAN – Storage array.
d] To setup loadbalanced webcluser using cluster aware Linux file system etc.

In this tutorial you will learn how to have a fully functional Linux iSCSI SAN using tgt framework.

RAID 5 vs RAID 10: Recommended RAID For Safety and Performance

Posted on in Categories File system, FreeBSD, Hardware, Linux, OpenBSD, RedHat/Fedora Linux, Storage, Suse Linux, UNIX, Windows server last updated October 22, 2008

A Redundant Array of Independent Drives (or Disks), also known as Redundant Array of Inexpensive Drives (or Disks) (RAID) is an term for data storage schemes that divide and/or replicate data among multiple hard drives. RAID can be designed to provide increased data reliability or increased I/O performance, though one goal may compromise the other. There are 10 RAID level. But which one is recommended for data safety and performance considering that hard drives are commodity priced?

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?

CentOS / Red Hat Enterprise Linux 5.2 Poor NFS Performance and Solution

Posted on in Categories Apache, CentOS, data center, File system, High performance computing, Howto, Linux, Linux distribution, Networking, package management, RedHat/Fedora Linux, Security Alert, Storage, Sys admin, Troubleshooting, Tuning last updated August 22, 2008

A few days ago I noticed that NFS performance between a web server node and NFS server went down by 50%. NFS was optimized and the only thing was updated Red Hat kernel v5.2. I also noticed same trend on CentOS 5.2 64 bit edition.

How To Measure Linux Filesystem I/O Performance With iozone

Posted on in Categories File system, High performance computing, Linux, Linux distribution, RedHat/Fedora Linux, Storage, Sys admin, Tips, UNIX last updated July 4, 2008

IOzone is a filesystem benchmark tool. The benchmark generates and measures a variety of file operations. Iozone has been ported to many systems and runs under many operating systems including Windows, UNIX, Linux and BSD. This article gives you a jumpstart on performing benchmark on filesystem using iozone a free Filesystem Benchmark utility under Linux.