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Old 12-27-2007, 08:31 PM   #1
jays2001
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Question Drobo style NAS from Linux distro.


I have been looking at the Drobo unit but it has a couple of shortcomings that I am sure a Linux distro must be able to overcome. Firstly, it is a USB device with no Ethernet and secondly it is fairly expensive.

My requirements are as follows.

1) Support for multiple drives presented to the network as one large drive.
2) Data protection, like a raid array.
3) The ability to add and remove drives without loosing data integrity and without having to rebuild the array.
4) Not requiring all drives to be of the same capacity.

I have looked into FreeNAS, NASLite, ClarkConnect and Openfiler and none of these support points 3 and 4 on the list.

Are there any fairly easy to configure distros that will achieve this?

--
Jay
 
Old 12-27-2007, 08:35 PM   #2
jays2001
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oh, and...

5) Must support SATA drives.
 
Old 12-28-2007, 01:45 PM   #3
jays2001
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Does the lack of replies mean there is no such distro, or is the forum just quiet today?
 
Old 12-28-2007, 02:51 PM   #4
andrewdodsworth
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I suspect that the big silence is because a) Linux is perfectly capable of doing all you need and b) maybe there have been similar questions already answered here. Have a look at LVM which I use on my Linux box and see if that does all you need.
 
Old 12-29-2007, 09:38 AM   #5
jays2001
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I didn't find an answer when I searched, and I have already looked into LVM but according to its Wikipedia page...

Quote:
Originally Posted by Wikipedia
LVM cannot provide parity-based redundancy, as with RAID4, RAID5 or RAID6.
And that was number 2 on my list, although I suppose I could have been clearer about not wanting to use mirroring (RAID1) for which I apologise.

Thanks for trying though.

I have come accross unRAID earlier today and am just about to test the free vertion but that only supports 3 drives and has to boot from USB, I would prefer a hard drive install. It is also a commercial product for larger arrays but it isn't expensive so if there are no other options I may go with it.

Will let you know how my testing goes.
 
Old 12-29-2007, 12:01 PM   #6
andrewdodsworth
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RAID and LVM are independant so it should be perfectly possible to set up RAID first to give you the physical redundancy and then LVM on top to give you the ability to resize logical disks on the fly. However, it really depends on what you need and want to do - good luck.
 
Old 12-29-2007, 12:36 PM   #7
lazlow
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Jay

#3 is a hardware issue and not a software issue. You will need a raid setup that allows hot swapping. Any mirroring Raid setup(#2) will HAVE to rebuild/restore the new disk in order to function.

#4 Most (if not all) Raid setups (#2) will require that the drives all be the same size. If you blow one drive (say320gig) and you try to replace it with another smaller drive (say 250gig) how is that going to work (it cannot)?

I do not think you have a working understanding of Raid and its capabilities.

LVM as stated is a totally separate issue from Raid. It will allow you to span many drives to appear as one drive (volume) and to be able to dynamically expand/contract that volume. The downside of LVM is that when it develops a problem it can rapidly turn into a nightmare. If you do use LVM on Raid, the Raid will not offer any real protection against LVM headaches (drive problems yes, LVM problems no). It will also add one more layer of complexity, one more thing that can fail.

An easier way than LVM is to just use a "mother" drive(or array) and place the mount points of all the other drives on the mother drive. Then if you want to add/remove a given drive all you have to do is mount/unmount the drive. This will not allow one file to span drives, but it will allow multiple drives to appear as a single drive. You can use this in conjunction with raid as well, only you will mount arrays instead of drives.

Excluding those limitations any Linux distro will do what you want. You listed some excellent options in your first post.
 
Old 12-31-2007, 06:52 AM   #8
jays2001
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OK, I have been playing with the free version of unRAID and it does exactly what I was looking for. You can mix any number of different sized drives into the array and the only restriction is that the largest must be the parity drive for obvious reasons. It also doesn't stripe data across the other drives meaning if two drives should fail at the same time you will only loose the files on those drives and not the entire array like you would with a raid setup.

It does have some shortcomings...

Firstly it will only boot from a USB key and I would far prefer a hard drive install.

Secondly it's boot time is horrific, it takes about 15 minutes to start up on my machine and it isn't a slow machine, FreeNAS booted in about 40 seconds on the same hardware.

Finally, it has almost no features. This is not in it's self a bad thing since it does what it is supposed to do but even simple things like shutting down the server remotely are not possible from the web interface and require you to SSH into the box. I can do that but no one else in my household could.

In conclusion it would be really nice to see this sort of functionality built into one of the more established distros like FreeNAS.
 
Old 12-31-2007, 07:25 AM   #9
dyasny
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freenas and openfiler easily support raid0, raid1 and raid5. probably should be able to work with raid 10, 50, 6 and 60. but no matter what you do - they array has to be rebuilt. if you get a NAS server with a good raid controller - it will be able to rebuild seamlessly. on linux software raid, the rebuild is not much of a hassle anyway.
 
  


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