RAID 5 Versus "UNRAID" - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 10 Old 01-07-2006, 09:02 AM - Thread Starter
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RIght now I am working off 3 external USB drives of 200 to 250 GB sizes. They are full and I need to expand my system so I was looking at making a RAID 5 system. Problem is that I think it will be too expensive and wasteful to do so. Here is why and please correct me if these are misconceptions:

1) When I build the RAID5, all the dirves have to be empty so the data can be striped across them, so I would need to somehow backup all the ripped DVD movies, or just rerip all of them (probably 80 hour time investment the way I like to specially rip and edit out movies/ TV shows).

2) The drives I have now are of different sizes. I think 2 are 250 and one is 200 but I need to check (All 3 might be different). All drives on a RAID have to be the same size so this basically means I have hard drives I cant use.

3) I need to make an investment and spend money on hard drives I wont need for two years because if I want to expand the RAID storage later, I need to delete all the data, rerip everything to the nwe larger RAID so the data is triped across all the drives (Even the new ones I added). This means that I cant hold off and buy cheaper HDD when I need them, I have to pay more money and buy them now when I dont need them (Assuming the price of HDDs continues to decrease which is nearly certain). Possibly even buying enough storage for 3 or 4 years because rebuilding or adding storage sounds complicated.

This leads me to believe the UNRAID system being sold here on the forums might be a better solutino and buy a DVD burner and burn backups of my ripped DVD/TV shows so that in the event of HD failure (when not IF it happens), I can just copy from the DVD instead of reripping/editing intros/credits. The UNRAID wont give me any data proction but I can spend the time and money I save from building a RAID 5 on burning DVD backups.

Comments?
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post #2 of 10 Old 01-07-2006, 09:58 AM
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First Raid5 is expensive and all the drives need to be of the same side. But some claim you can add same size drives to the array. It can be challenging and might not work or worse corrupt the entire array.

As for Unraid I have it and it works like a champ and it does offer data protection if one drive fails. Also if more than one drive fails you will then only lose the data on the failed drives. Oh and yes you can use different size drives as long as your parity drive is the largest.

So basically for the unraid server buy the hardware and 2 more hard drives say 300gb or bigger (these have rebates everyother week it seems). Set up the unraid server with the two drives. Transfer all you movies off your largest drive to the server. Add that drive to the server and repeat until all 3 hard drives have been transfered to the server. This then leaves you with 200gb free on the server after you install the last drive.

HTPC with MCE
UnRaid Media Server - lots of storage and growing
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post #3 of 10 Old 01-07-2006, 10:29 AM
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1) When a RAID set is built, all contents on the drive are wiped. Somehow, you would need to move the data elsewhere.

2) Most (if not all) RAID cards will use any drives. Howvever, the set of drives willbe at the smallest drive capacity (3x73 GB and 2x 26 GB ends up as 5x36 and the excess is just not available form the 73 drives).

3) Depending on the controller, you would be able to add capacity and have the raid set incorporate drives. You want Online Capacity Expansion or some such feature that would allow more disks to be added. you'd start with a 3 disk RADI5 and then add two more at a later date. Using diskpart form windows, you could add capcity to the dynamic disk.

Make sure you understand how to add space to the raid and understand just how it works so you're not surprised when you need to do it. The wolustions can get pricey, but a 5 disk ata cage (fits in 3x5.25 bays) runs about $150. Add $150 for a controlelr card and $50 for 160 GB SATA drives (check anandtech for hot deals on SATA drives) after some rebates. Not cheap, but the time it takes to burn 40-50 dvd's may make it all worth it. Check 2cpu for some inexpensive (used) raid options as well. The members over there typcially have higher-end PC hardware and you may find something that fits.

You may even find someone local who can "lend" some disk space to facilitate changinng everything out for you.

Good luck,
EH
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post #4 of 10 Old 01-08-2006, 05:44 AM
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Well, you can get around some of the limitations you mention if you run Linux software RAID with EVMS as a management tool:

1) The drives that you create the array from do indeed need to be empty, however you can create an initial array from just 2 drives (as a degraded 3-drive array), copy some data to it, then add an extra drive to it, and so on until you have an array of as many drives as you like. So you'll need to clear at most 2 drives-worth of data, for any sized array.

2) Correct; an n-drive array will be (n-1)*size_of_smallest_drive. So you're wasting space if your drives aren't the same capacity. This is in my mind the biggest (though not the only) advantage that the unraid system brings in terms of flexibility.

3) If you're using EVMS, then you can add drives to the array to expand it without having to back up the data on it, so this shouldn't be a problem.

See http://evms.sourceforge.net/ for more info. And good luck.
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post #5 of 10 Old 01-08-2006, 09:16 AM
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Would Sun's new ZFS work here, too? One could build use OpenSolaris.

http://www.opensolaris.org/os/commun...s/zfs_last.pdf
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post #6 of 10 Old 01-08-2006, 09:50 AM
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Quote:
Originally Posted by The Belgain
Well, you can get around some of the limitations you mention if you run Linux software RAID with EVMS as a management tool:

1) The drives that you create the array from do indeed need to be empty, however you can create an initial array from just 2 drives (as a degraded 3-drive array), copy some data to it, then add an extra drive to it, and so on until you have an array of as many drives as you like. So you'll need to clear at most 2 drives-worth of data, for any sized array.

2) Correct; an n-drive array will be (n-1)*size_of_smallest_drive. So you're wasting space if your drives aren't the same capacity. This is in my mind the biggest (though not the only) advantage that the unraid system brings in terms of flexibility.

3) If you're using EVMS, then you can add drives to the array to expand it without having to back up the data on it, so this shouldn't be a problem.

See http://evms.sourceforge.net/ for more info. And good luck.
What I understand about LVM and EVMS is that you can expand the VOLUME, but not the array itself. For that there is no core component of linux (there is a 3rd party utility, but it totally screwed my entire array when I tried it). So if you wanted to expand your storage after fully utilizing your exisiting space, you would need to add a 2nd array to add to your EVMS volume. This causes you to lose 2 disks worth of space to parity instead of just one.

Again, I'm not an expert, but that's my understanding of how volume management works with RAID on linux...
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post #7 of 10 Old 01-08-2006, 11:05 AM
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I too am running the UNRAID system. so far I've found it to be quite flexible and expands as I need it too. I was able to corral up a bunch of old drives plus some new ones to get my system up over a Terrabyte. Transferring data was as simple as copying it over. There are some things I might like to see changed with the system in the future and the author seems pretty responsive to suggestions and open about capabilities. For now it's suiting my needs just fine! I've even had a drive failure - parity drive - and no data was lost. In fact I ran with a dead parity drive for days until I could get it replaced - no issues. I have a couple more 300Gig drives to drop into it that I've just not had time to put in (lol) but having done this before already I know it will simply be a matter of adding them and recalculating parity for the array.

RAID5 to get this level of protection would require hotspares - no thanks. I've heard too many horror stories form people who's RAID has flipped out and consumed itself to want to risk that - this is too big to backup!

Do the UNRAID. Maybe get a smaller case for starters and get the Promise cards from EBAY - you won't regret it.
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post #8 of 10 Old 01-08-2006, 12:50 PM
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Quote:
Originally Posted by jcruse
What I understand about LVM and EVMS is that you can expand the VOLUME, but not the array itself. For that there is no core component of linux (there is a 3rd party utility, but it totally screwed my entire array when I tried it). So if you wanted to expand your storage after fully utilizing your exisiting space, you would need to add a 2nd array to add to your EVMS volume. This causes you to lose 2 disks worth of space to parity instead of just one.

Again, I'm not an expert, but that's my understanding of how volume management works with RAID on linux...
No, EVMS also lets you expand the underlying RAID5 array (independently of whether you've got an LVM container on top of it or not). I know because I've done this to one of my RAID5 arrays. I went from 3x160GB with a capacity of 320GB, to 4x160GB with a capacity of 480GB.

See http://evms.sourceforge.net/user_guide/#resizemdreg in the EVMS user guide for more info...
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post #9 of 10 Old 01-08-2006, 06:53 PM
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Quote:
Originally Posted by The Belgain
No, EVMS also lets you expand the underlying RAID5 array (independently of whether you've got an LVM container on top of it or not). I know because I've done this to one of my RAID5 arrays. I went from 3x160GB with a capacity of 320GB, to 4x160GB with a capacity of 480GB.

See http://evms.sourceforge.net/user_guide/#resizemdreg in the EVMS user guide for more info...
I read the guide you linked to...nothing on how to actually expand the array (but did contain how to expand the volume)

Are you sure you aren't running a 3-drive RAID array with a 4th disk in your volume (unraided)? That's what it sounds like to me... If you manually fail your 4th drive, can it recover it's contents??? One easier way to tell: when you run mdadm --detail, does it indicate the 4th drive?
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post #10 of 10 Old 01-10-2006, 10:32 AM
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I have the Un-Raid system (starter kit) and it is running terrific. Without any issues. Speed is great and I am very happy.
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