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#300431 - 10/07/2007 15:36 RAID Empeg?
Robotic
pooh-bah

Registered: 06/04/2005
Posts: 2026
Loc: Seattle transplant
I know we've had loads of discussions about RAID arrays on the board and I've learned a great deal about them as a result. We're usually talking about home storage solutions- which is best, cheapest, most reliable, software vs. hardware, whatever- but I recently had a thought about RAID in the empeg.
Is this even possible?
It's easy for me to think 'Ah- my home-made RAID-5 box runs Linux and so does the empeg!', but I realize there are limitations that I have no clue about.

As 160GB drives are now easily available and I don't have even 100GB of files to put on my empeg, would a 'mirrored empeg' protect me from the hardships of a dead drive?
Would a 'striped empeg' relieve the caching problems I've read (very little) about?
Has anyone ever thought about this before? I can't be the first.
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10101466 (2x60GB, Eutronix/GreenLights Blue) (Stolen!)

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#300432 - 10/07/2007 15:40 Re: RAID Empeg? [Re: Robotic]
mlord
carpal tunnel

Registered: 29/08/2000
Posts: 14496
Loc: Canada
Quick summary:

(1) The default/Hijack kernels do not include RAID support, but it can be configured with a custom kernel build.

(2) The empeg filesystem / startup would require some minor hacks to make it work.

(3) It won't help with anything, other than avoiding loss of tunes when one of the two drives dies.

(4) Uploading tunes to the empeg will be slower; system startup will be slower.

Cheers


Edited by mlord (10/07/2007 15:42)

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#300433 - 10/07/2007 16:00 Re: RAID Empeg? [Re: Robotic]
wfaulk
carpal tunnel

Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
I tried it in the past. It's harder than you might expect. I posted my empeg raid notes online.
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#300434 - 10/07/2007 16:06 Re: RAID Empeg? [Re: wfaulk]
Robotic
pooh-bah

Registered: 06/04/2005
Posts: 2026
Loc: Seattle transplant
Thanks Mark and Bitt!

It was just a thought that piqued my curiosity.
_________________________
10101311 (20GB- backup empeg)
10101466 (2x60GB, Eutronix/GreenLights Blue) (Stolen!)

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#300435 - 10/07/2007 17:36 Re: RAID Empeg? [Re: Robotic]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31600
Loc: Seattle, WA
Quote:
would a 'mirrored empeg' protect me from the hardships of a dead drive?

Even if you could get RAID working on the empeg, it wouldn't protect you from the hardships of a dead drive. You still have to go through the same rigamarole when a drive dies. The only thing it protects you from is losing all the MP3s on that hard disk. And it only protects you a little bit, not as much as a true backup would protect you.

When it's all said and done, it's easier just leaving the MP3s on your computer after you send them to the empeg. That's your best bet for backup of the MP3 files.
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Tony Fabris

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#300436 - 10/07/2007 18:00 Re: RAID Empeg? [Re: tfabris]
Robotic
pooh-bah

Registered: 06/04/2005
Posts: 2026
Loc: Seattle transplant
I've learned today that the drives aren't mirrored- only some of the partitions are.
<slaps forehead>
_________________________
10101311 (20GB- backup empeg)
10101466 (2x60GB, Eutronix/GreenLights Blue) (Stolen!)

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#300437 - 10/07/2007 18:02 Re: RAID Empeg? [Re: Robotic]
mlord
carpal tunnel

Registered: 29/08/2000
Posts: 14496
Loc: Canada
Quote:
I've learned today that the drives aren't mirrored- only some of the partitions are.
<slaps forehead>


On modern kernels (not empeg kernels), the drives are normally mirrored, and then partitioned with "LVM".

Cheers

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#300438 - 10/07/2007 18:11 Re: RAID Empeg? [Re: mlord]
wfaulk
carpal tunnel

Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
Regardless, there's not much difference. I got it to run successfully and mirror all relevant partitions (I didn't bother with the swap partition, basically).

That said, I agree that it's a little silly.
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Bitt Faulk

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#300439 - 10/07/2007 18:16 Re: RAID Empeg? [Re: tfabris]
wfaulk
carpal tunnel

Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
Quote:
And it only protects you a little bit, not as much as a true backup would protect you.

Well, that's both true and not.

It prevents you from having downtime. If you had a drive fail while on the road, you could carry on with only a reboot.

It also prevents you from having to restore from backup, which can be a pain. However, the replacement drive has to copy all of the data from the remaining drive. On an always-on computer, this isn't an issue, but it took me several hours to sync a 10GB mirror, during which time the empeg had to remain powered on. Powering off before completion requires that the procedure restart from the beginning.
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Bitt Faulk

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#300440 - 11/07/2007 23:42 Re: RAID Empeg? [Re: Robotic]
FireFox31
pooh-bah

Registered: 19/09/2002
Posts: 2494
Loc: East Coast, USA
RAID 5 a pair of CF controllers which each support two cards. Watch the parity bits fly!!
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FireFox31
110gig MKIIa (30+80), Eutronix lights, 32 meg stacked RAM, Filener orange gel lens, Greenlights Lit Buttons green set

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