Author Topic: DRU & PPU Optimization for Variety of Drives  (Read 1860 times)

Offline xioustic

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DRU & PPU Optimization for Variety of Drives
« on: November 24, 2012, 02:46:23 am »
Hey guys,

I run a HTPC Server that hosts about a RAID5 (hardware enclosure) of 4x2TB for an effective 5.5TB of space. I've got about 100GB free! This year I settled would be the year to expand my storage.

I have another server that I think I would like to use FlexRAID on (seriously contemplating a full license). I'll retire the RAID5 hardware enclosure (already have a buyer) but keep the 2TB drives. I'm just now learning about FlexRAID, but I've determined that for my current storage needs, Snapshot would be perfect. I mostly just store movies/TV shows/music, etc. This is static data that maybe has new files added every 2-3 days (in large amounts).

However, I'm going to have quite a mish-mash of drives. I've got a question on optimizing everything. First off, here's my current list of drives:
 - 2x3TB Internal
 - 4x2TB Internal
 - 1x2TB External
 - 1x500GB External

Which ones do I span for DRUs? Which ones do I use for PPUs? I figure I want approximately 1 PPU for every 5-6 DRUs...

My ideas:
- Scenario 1: Do I just make 1x3TB the PPU, span the 1x2TB and 1x500GB Externals, and have an effective 6 DRUs (1x3TB, 1x2.5TB, 4x2TB)?
- Scenario 2: Do I make a spanned 6TB PPU for the 2x3TB, make a 6TB DRU from spanned 3x2TB, and one last DRU with a combination of the remaining (2TB+2TB+.5TB)?

And for both Scenario 1 and Scenario 2, what would be my effective pooled available space? Would any of that available space not be part of the parity protection?

Also, is it important that I strip the externals from their enclosures so that they're internal? One is USB 3.0, one is USB 2.0.

Thanks guys, appreciate the help! (Hopefully I'm posting in the right place.)

Offline DrBlaze

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Re: DRU & PPU Optimization for Variety of Drives
« Reply #1 on: November 24, 2012, 07:51:42 pm »
I'll try to answer most of your questions.

#2 is bad for a number of reasons (spanned PPU, overly large - you lose 6TB of space, if you ever want to add another ppu you will lose 12TB :o)

So I would have:

PPU  =3TB
DRU1=3TB
DRU2=2TB
DRU3=2TB
DRU4=2TB
DRU5=2TB
DRU6=2TB ...usb3 ext drive may work fine as-is, we don't have much feedback from users about usb3 speeds with Flexraid.

The question is the 500GB. If you def want to add it you should remove it from enclosure and span it with a 2TB (usb2 and Flexraid don't mix well, do a search in forums for usb2 and read all about very slow speeds).  I would leave it out the raid and use it as a temp drive.  I'm not sure if you use utorrent, but downloading directly to the array is a bad idea and most people have temp drives.

The size of your pool will be the sum of all your DRUs. 

"Would any of that available space not be part of the parity protection?"
I'm a little uncertain what you mean by this so I will answer it in 2 different ways:

The PPU is your parity protection, once your array has been built it will be unavailable to you and you should never try to access it.  Everything on your DRUs will be protected unless you purposely exclude it (metadata or other data which changes frequently).

Offline DarkKnight

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Re: DRU & PPU Optimization for Variety of Drives
« Reply #2 on: November 24, 2012, 09:37:59 pm »
Is spanning a PPU a bad idea?

Offline xioustic

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Re: DRU & PPU Optimization for Variety of Drives
« Reply #3 on: November 25, 2012, 12:19:29 pm »
Thanks for your answer DrBlaze!

The question is the 500GB. If you def want to add it you should remove it from enclosure and span it with a 2TB (usb2 and Flexraid don't mix well, do a search in forums for usb2 and read all about very slow speeds).  I would leave it out the raid and use it as a temp drive.  I'm not sure if you use utorrent, but downloading directly to the array is a bad idea and most people have temp drives.

That seems about right, I wasn't sure what to do with that 500GB, but as a temp drive that seems like a good idea. I don't typically download with uTorrent, it's usually SabNZBD or something ripped/recorded myself. I think I was originally planning to use the OS drive as the temp drive, which is about 1TB in size.