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PROUHD: RAID for the end-user.

pierre — Wed, 14 Apr 2010 05:23:02 +0000

RAID has still not been adopted by most end-users despite its inherent quality such as performance and reliability. Reasons such as complexity of RAID technology (levels, hard/soft), set-up, or support may be given. We believe the main reason is that most end-users own a vast amount of heterogeneous storage devices (USB stick, IDE/SATA/SCSI internal/external hard drives, SD/XD Card, SSD, …), and that RAID-based systems are mostly designed for homogenous (in size and technology) hard disks. Therefore, there is currently no storage solution that manages heterogeneous storage devices efficiently.

In this article, we propose such a solution and we call it PROUHD (Pool of RAID Over User Heterogeneous Devices). This solution supports heterogeneous (in size and technology) storage devices, maximizes the available storage space consumption, is tolerant to device failure up to a customizable degree, still makes automatic addition, removal and replacement of storage devices possible and remains performant in the face of average end-user workflow.

Although this article makes some references to Linux, the algorithms described are independent of the operating system and thus may be implemented on any of them.

Note: this article has been published in HTML format at www.linuxconfig.org

Dealing with ssh “hidden” stuff: config file

pierre — Wed, 29 Jul 2009 17:51:32 +0000

If you use ssh a lot, you may sometimes feel tired giving same options all the time for the same server.

For example if you have an account ‘alpha’ on a server called ‘tarentula’ you may use the following command:

ssh alpha@tarentula

You may simplify your life: insert the following lines into your .ssh/config:

Host tarentula
    User alpha

Then, you can just type:

ssh tarentula

and you will get logged in ‘tarentula’ with the ‘alpha’ account.

I admit, this is not very impressive. But consider the following lines into your ~/.ssh/config:

Host tarentula
    User alpha
    ForwardX11 yes
    ForwardX11Trusted yes

Host *
    Compression yes

This basically means: for the ‘tarentula’ host given on the command line (this is different than the real host, see below): forward my X display (like if you did a ssh -X tarentula); and for all hosts (including tarentula), enable compression.

Better, if, for some reasons, you are behind a firewall, you can still access to an external server using the following:

Host tarentula
    ProxyCommand corkscrew proxy.company.com 8080 %h %p

Of course, corkscrew should be installed on your machine.

Finally, if you use virtualisation, you may have setup some ssh tunnels in order to access your various virtual machines. But you end up having to type ssh commands such as this one:

ssh -p 22024 beta@10.0.0.10

to enter as ‘beta’ in the 24th virtual machine that 10.0.0.10 is currently running. A config file such as this one:

Host vm24
    HostName 10.0.0.10
    Port 22024
    User beta

will make your life much simpler:

ssh vm24

Choosing the right File System Layout under Linux

pierre — Tue, 21 Jul 2009 11:34:33 +0000

As you may probably know, Linux supports various filesystems such as ext2, ext3, ext4, xfs, reiserfs, jfs among others. Few users really consider this part of a system, selecting default options of their distribution’s installer. In this article, I will give some reasons for a better consideration of the file-system and of its layout. I will suggest a top-bottom process for the design of a “smart” layout that remains as stable as possible over time for a given computer usage.

Note: this article has been published in HTML format at www.linuxconfig.org