Re: Linux Software RAID on External Drives

Hi,

Well, i'm running a raid-0 setup on 2 external 160Gb disks
and getting quite ok performance.
What you might need to keep in mind is that there are a few small
problems with running a md-setup on firewire-units, and that is that the
automatic detection of the raid on the device is not automaticly
detected so you need to do a raidstart on the device after the devices
have been detected.

I would reccommend using firewire 400/800 for external disks. I have
tried running usb devices here also, but they seem to have a high
latency and when using the disks for small files it's just too slow.
With firewire you might get a few mb/s less than USB since USB2.0 is
480Mbit, but since firewire has a lower latency it feels much faster
than USB2.0.
Thoe what i have been planning to do after i have moved i will probably
buy some cheap MB with some IDE-controller and then just smack the box
full of disks and enable powersave mode on them also. Then just run a
Gbit lan or if it's close enough, run a firewire 400 cable to the other
box (depending on how fast the disks can read the data.)

What you also could consider is one of those LAN-disks with raid5 that
you can access with smb or nfs. Those are probably much better, and less
noisy than having a complete box with disks in it. (more than 2 drives
and you will proably need a couple of fans in the box also..

So i would reccomend to you is to go this list and see what you really
need.

1. How much space do you need?
        4*160Gb?
        2x160Gb?

2. How fast do you need to copy data to/from the disks?
        fw400 - for me it gives around 25Mb/s read/write on 2 160Gb 5400
        disks.
        fw800 - Havent tried anything on it, but most stuff are more
        expensive.

3. How much data is critical? (raid 1 or 5?)
        Running a small 30Gb (30+30) raid1 here and then a raid0 on the
        remaning space. Also mirroring my laptop-disk to the
        firewire box.

4. How much data is non-critical? (raid 0)
        hmm... 4x160Gb disks? Got tons of DivX'es? :D

5. Whats your budget for this?
        Here a MAP-304 box costs something like $800.
        (4 3.5" IDE devices)

6. How quiet do you want it?
        Multiple fanless firewire boxes?
        One big box with fans?

/P

On Thu, 2004-09-16 at 19:08, Brice Burgess wrote:
> I'm getting rid of my desktop (* http://www.guidospaper.com/comp.html
> ). It is heavy, dusty, and will be better off with a buddy of mine. I'm
> going to build a mini-ITX form factor computer ( or perhaps go with a
> Shuttle XPC system ). The point is; I'm aiming for a tiny silent
> computer running Linux with all its perripherals attatched externally
> (ie. external CDR, floppy and hard drives). I'll likely have a 20GB
> internal notebook drive and slim CDROM to boot my system from. Of most
> importance is my external storage unit, known as the "Barn". My "Barn"
> currently consists of 2x120GB ATA drives in a Linux software RAID-1
> Array. The "Barn" holds all of my projects, digital media collection,
> and everything else I can't afford to loose. In the process of building
> my new system, I want to expand and modularize the Barn. I think 4x160GB
> IDE drives attatched to a bridgeboard of some kind and placed in a
> software RAID-5 array is optimal. The external chasis will have a small
> low wattage power supply unit built in to power the drives. These are my
> plans.. and I've been brainstorming ideas for awhile now on how to setup
> an external redundant storage unit in the most cost-effective manner.
>
> Does anyone have experience using Linux software raid (mdtools) to
> create disk arrays by linking multiple external drives together? Is it
> reliable? What are the preffered busses -- USB2, IEEE 1394, Fiber, etc?
> And above all, what do you think will be the most cost-effective (yet
> still viable) solution?
>
> As ever,
>
> Brice Burgess
>
>
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Received on Fri Sep 17 19:42:02 2004