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Old Aug 9, 2012, 04:39 AM   #1
RedTomato
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Dirt cheap USB dual RAID1 external enclosure?

Hiya,

I have a Time Capsule, which is nearly full, so I want to move some archives off that into a new HDD enclosure.

So I'm looking for a dirt cheap dual bay external enclosure. I already have a few spare HDDs to put in it so I don't want to spend too much more.

I want it to be RAID1 (mirrored). Absolutely vital is the ability to take one HDD out of the mirror and access the files in another computer or enclosure. I think this means it must be software RAID1, not hardware.

This is for home use and archival only, so I don't mind if it's slow.

I found this USB dual-bay SATA enclosure - what do you think?

http://www.amazon.co.uk/Dual-SATA-Ex...503811&sr=1-78

It doens't seem to do hardware RAID1, only RAID 0 (striping) and JBOD, which seems fine, as I will be doing RAID1 in software anyway (if that is possible!)
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Old Aug 9, 2012, 04:45 AM   #2
rctlr
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Well that Amazon link points to a Raid0/jbod array, no good for your needs.

http://www.amazon.co.uk/IB-RD3219StU...783400-7870335

might give you what you need.
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Old Aug 9, 2012, 05:17 AM   #3
RedTomato
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Quote:
Originally Posted by rctlr View Post
Well that Amazon link points to a Raid0/jbod array, no good for your needs.

http://www.amazon.co.uk/IB-RD3219StU...783400-7870335

might give you what you need.
Thanks for the reply - but as I said, the Raid0/jbod array might meet my RAID1 needs by setting up raid1 in OSX.

I've had bad experience with raid5 failures, so ease of recovery is vital, especially if I need to come back to this box a couple of years in the future. I gather that while a hardware raid1 box might be faster, many of them won't let me access the files via taking a drive out and using it elsewhere.

So hopefully software raid1 via osx will give more hardware independence at the price of losing some speed, which I'm happy with, as this box will be rarely used.

Do you think that's workable? I honestly don't know if OSX can run software raid1 via a single USB lead to a dual bay enclosure?
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Old Aug 9, 2012, 07:17 AM   #4
rctlr
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Personally I've always let the hardware deal with raid configuration and management, rather than using software to mirror - in case I've had to rebuild the server/computer. I'd pay the extra.

I've not used the macs raid manager, I would hazard a guess that IO would be a big overhead unless you had decent fast drives (10k+).
I would presume there would be a way to keep a backup of configurations and mappings if your imac needs a reinstall.
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Old Aug 9, 2012, 08:17 AM   #5
RedTomato
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Quote:
Originally Posted by rctlr View Post
Personally I've always let the hardware deal with raid configuration and management, rather than using software to mirror - in case I've had to rebuild the server/computer. I'd pay the extra.

I've not used the macs raid manager, I would hazard a guess that IO would be a big overhead unless you had decent fast drives (10k+).
I would presume there would be a way to keep a backup of configurations and mappings if your imac needs a reinstall.
Time Capsule gives me a full hourly backup (this is on a macbook BTW). I've done two full system restores from it and various small files so it works fine.

Someone has now given me one of these:

http://www.play.com/PC/PCs/4-/159577...e/Product.html

Seems to work fine with one drive, but drops connections / sometimes refuses to mount drives with two drives installed.

EDIT: I've now figured this is because the power supply I got with it is only 12v 2amps, but the enclosure says on the label it requires a 12v 3amps power supply. (The drives I have all need 1.5 amps each.)

So now I need to find or buy a cheap 12v 3amp wall wart. Oh well, lucky this is just a home project.

Last edited by RedTomato; Aug 9, 2012 at 08:22 AM.
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Old Jan 28, 2013, 02:58 PM   #6
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Update 6months later

Just a simple box with 2 bays and a single USB lead. Dirt cheap - about 25.
http://www.play.com/PC/PCs/4-/159577...e/Product.html

The supplied power adaptor was definitely underpowered - 2 amps - only enough for 1 drive. I finally got round to getting a 12v 4 amp power adaptor off eBay - enough for both drives plus the case fan - and the box worked perfectly fine with no drops or mysterious missing drives.

Tested it with a pair of 300GB drives. OSX Disk Utility was able to put them into RAID1 with ease.

Test 1. Standard Use
Data transfer was about 20MB/s indicating that OSX is seeing them as two separate drives and sending 20MB/s to each drive at the same time, for a total of 40MB/s down the single USB2 lead, hitting max USB2 bandwidth.

Test 2. Power Failure
Unplugged the drives in the middle of a transfer. Ejection warning came up. Replugged in the drives & all seemed fine. Disk Utility saw no need to rebuild the drives (this time anyway).

Test 3. Disk Failure
Powered down, disconnected 1 disk, then powered back up. OSX took several seconds longer to mount the disk, then mounted it fine. No warning was given that a disk had failed. I was able to copy and write to the single drive without any problems.

Looking at the RAID in Disk Utility shows the RAID in degraded state, but only the mount points were shown (disk1s1, disk2s1 etc) not the names I had given the disks (Archive1, Archive2 etc) if a disk had failed by itself, I wouldn't know which one was the dead one.

As I already knew which one I'd unplugged, I took this chance to label the drives with their system mount names under OSX - Disk1s1 and Disk2s1. Hopefully the mount names will stay the same but I wouldn't bet on it.

Test 4. Rebuilding.
Powered down the enclosure and reconnected the missing drive and powered it up again. Again after a short delay the RAID came up on the desktop with no indication that anything was happening. Looking at Disk Utility showed that the RAID was being rebuilt.

I only had a single 1GB file on the otherwise empty 300GB RAID1 but the rebuilding seemed to take forever. I left it for nearly an hour and rebuilding seemed to be about 10% complete, so about 10 hours to do the entire (empty) disk. Seemed to be checking every sector at 20mb/sec.

Conclusion

I'm happy with this enclosure for making a RAID1 archive for rarely used files that I won't access very often. I wouldn't be happy if my only copy of valuable files was on this - too low-cost and fragile. Any rebuild would put the remaining drive through 10 hours of high temperature stress and workload. I'll keep another copy on a third disk in a different location - aka 'three copies in two locations'.

Last edited by RedTomato; Jan 28, 2013 at 03:04 PM.
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