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prbox
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Joined: 12 Feb 2004
Posts: 33
Location: Somerset, UK

PostPosted: Sun May 13, 2007 2:28 am    Post subject: Expandable file system Reply with quote

Hi,

I've been looking around for 3 days now for a filesystem. This all came about once I saw the demo of 'Drobo' at http://www.drobo.com/

I have a lot of data, music mixes, raw video from DV cams and GB's of digital photos. Sure I could back this all up to DVDs or such but how do I know that data is safe. There is a lot to be said for maintaining a live filesystem. I want something that allows me to easily expand my storage without reconfiguring. That I can easily replace a drive when it goes down, and it doesn't matter if I change from IDE to SATA, or use a bigger drive without losing space to a unused portion.

I did check out ZFS (not available in kernel land for linux yet), as much as trying to get Solaris10 and then opensolaris to run on my Asus SK8N, of which I find out that my SATA controller is not supported. Eventually I got FreeBSD 7.0-Current up and running with ZFS and I'm in process of copying data onto a 2 dev RaidZ. However I now discover that you can't grow a RaidZ array. Though the ZFS documentation wasn't 100% clear on that.

Bear in mind when one wants to grow a filesystem, that it's not just a simple case of breaking up the current array adding a device and rebuilding. What happens to that 2TB of data in the meantime.

Basically I'm looking for a filesystem for linux that does what the drobo unit does. If you haven't seen the demo then take a look - there are some pretty neat ideas in there.

I need that my data is protected. Mirroring or whatever. That it;s easily expandable and also I can flexibly replace the devices. Perhaps I'll just have to settle for Raid1.

Your thoughts would be most appreciated.

Cheers,
Al
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mark_alec
Bodhisattva
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Joined: 11 Sep 2004
Posts: 6066
Location: Melbourne, Australia

PostPosted: Sun May 13, 2007 4:54 am    Post subject: Reply with quote

Moved from Gentoo Chat to Other Things Gentoo.
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highcaffeine
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Joined: 14 May 2007
Posts: 1
Location: D.C., US

PostPosted: Mon May 14, 2007 11:24 pm    Post subject: Re: Expandable file system Reply with quote

prbox wrote:
Basically I'm looking for a filesystem for linux that does what the drobo unit does. If you haven't seen the demo then take a look - there are some pretty neat ideas in there.

I need that my data is protected. Mirroring or whatever. That it;s easily expandable and also I can flexibly replace the devices. Perhaps I'll just have to settle for Raid1.


Have you considered something as simple as adding new drives in pairs using mirroring between them, extending an LVM partition to use the new space, then growing your filesystem on that partition? Or using one of the other RAID levels if you're adding more than two physical drives at a time. It won't be a brain-dead "slap a new drive in and It Just Works" setup, but if you're looking for a Linux-native (non-ZFS, non-dedicated-SAN) f/Free solution, that's pretty much it when you go about it ad-hoc like it sounds you will be.
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Cyker
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Joined: 15 Jun 2006
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PostPosted: Tue May 15, 2007 7:14 pm    Post subject: Reply with quote

Linux and Gentoo can do pretty much everything the drobo can do, but it doesn't come with such a nice automated interface so you get into documentation-and-command-line hell (Well, unless you use that administration app... can't remember wtf it's called now!!! It's like a graphical RAID+LVM manager thingy... damnit, what's it called?!)

My RAID 5 array for instance - Using the standard mdadm stuff, I can add another disk (Upto 5 plus whatever the Sil eSATA multiplexer can support), and swap out all the disks (albeit one by one) with bigger ones then grow the whole array to fit the new free space on the bigger disks.
And if one disk goes, I can carry on doing stuff, just need to swap out one of the drives and tell mdadm to add it to the array; The kernel handles all the re-integration.
(If two disks go I'm completely and totally fscked 'tho :shock:)


And you know what filesystem I use?

ext3 ;)
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meulie
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Joined: 17 Jun 2003
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Location: a Dutchman living in Norway

PostPosted: Mon Jul 07, 2008 9:42 pm    Post subject: Reply with quote

I also saw the Drobo and it looks pretty nifty! It would be so cool to just add a drive to my RAIDx-system, or replace an existing drive with a bigger one, and automagically get a larger storage volume... :-)
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Cyker
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PostPosted: Tue Jul 08, 2008 9:30 am    Post subject: Reply with quote

meulie wrote:
I also saw the Drobo and it looks pretty nifty! It would be so cool to just add a drive to my RAIDx-system, or replace an existing drive with a bigger one, and automagically get a larger storage volume... :-)


The Drobo is a bit odd there; If you have 4 80GB drives and swap one for a bigger one, you don't gain any space.
If you put a second bigger HD in 'tho, you do get the extra space.

Adding an extra drive in Linux with mdadm and RAID5 is pretty straightforward, 'tho it takes a long time for he array to re-organise itself.

Upgrading all the drives takes smegging ages as you have to swap each unit out individually, wait for the resync, repeat until all devices have been replaced, then grow the array.


The only thing I dislike about the Drobo is its lack of network support. You can buy an extra dongle for it which gives it network support, but it's very expensive for what it does.

Frankly, most NAS are a ripoff - I build this 4TB server for far less than the cost of a 4TB NAS and it does a lot more!
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Caffeine
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Joined: 17 Jul 2002
Posts: 401
Location: Melbourne, Australia

PostPosted: Wed Jul 30, 2008 12:08 pm    Post subject: Reply with quote

I'd love an implementation of BeyondRAID or whatever they're calling their RAID technology in Linux. Being able to buy a new HD which has the current best $ / GB and add it to your array and get some more space, without having to rejig everything would be great.

I like that Linux RAID 5 can grow - that's great, but soon enough, the size disks you used to build it won't be the best $/GB ratio.

Currently the best solution I've read was posted above - buy disks in pairs and RAID1 + LVM them. When it's time for more space, buy two more disks, RAID1 them and add them to the LVM.

If I was going to start working on this, and I'm no kernel developer, I reckon starting with FUSE to get your algorithms down would be the way to go.
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