Re: Proposal: non-striping RAID4

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I would like to bring this back to the attention of the group (from November 2007) since the conversation died off and it looks like a few key features important to me were left out of the discussion... *grin*

The original post was regarding "unRAID" developed by http://lime-technology.com/

I had an idea in my head, and "unRAID" has features almost identical to what I was thinking about with the exception of a couple deal breaking design decisions. These are due to the proprietary front end, not the modified driver.

Bad decision #1) Implementation is for a NAS Appliance. Files are only accessible through a Samba share. (Though this is great for the hoards of people that use it as network storage for their windows media center pcs.)

Bad decision #2) Imposed ReiserFS.

Oh yeah, and it's not free in either sense of the word.

The most relevant uses I can think of for this type of array are archive storage and low use media servers. Keeping that in mind...

Good Thing #1)
"JBOD with parity." Each usable disk is seen separately and has its own filesystem. This allows mixed sized disks and replacing older smaller drives with newer larger ones one at a time while utilizing the extra capacity right away (after expanding the filesystem.) In the event that two or more disks are lost, surviving non-parity disks still have 100% of their data. (Adding a new disk larger than the parity disk is possible, but takes multiple steps of converting it to the new parity disk and then adding the old parity disk back to the array as a regular disk... acceptable to me)

Good Thing #2)
You can spin down idle disks. Since there is no data striping and file systems don't [have to] span drives, reading a file only requires 1 disk to be spinning. Writing only requires 1 disk + parity disk. This is an important feature to the "GREEN" community. On my mythtv server, I only record a few shows each week. I would have disks in this setup possibly not accessed for weeks or even months at a time. They don't need to be spinning, and performance is of no importance to me as long as it can keep up with writing HD streams.

Hopefully this brings a new perspective to the idea.

Thanks,
Tony Germano
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