RAID set "Degraded": how to repair?

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RAID set "Degraded": how to repair?

Hi, I have a software RAID 0 set which apperas as "Degraded" in Disk Utility (boot OS X is not on it). I canot find a way to rebuild the set as the "Update" botton is always greyed out regardless what i select in the window.
Can anybody help me?
TIA
Simon

Message was edited by: majortom67

iMac 27" - Core i7, Mac OS X (10.6.2), 4Gbyte RAM - 1TByte HD - Ati 4850/512

Posted on Mar 9, 2010 5:54 AM

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Answer 1

The hatter

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Mar 9, 2010 6:44 AM in response to majortom67

So you use an external case, with a stripe array, and it says "degraded?"
Seems degraded is mentioned for mirror.
http://reviews.cnet.com/8301-13727_7-10330310-263.html
http://support.apple.com/kb/HT3305

And you created the array in Disk Utility.

Dual drive case, some of which have built in bridge that can enable its own RAID.

And you are doing this over a FW800 connection?

Is that basics?

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Answer 2

majortom67 Author

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Mar 9, 2010 6:59 AM in response to The hatter

No, I have 2 external HD each in its own box via USB2. I've discovered that I couldn't rebuild the RAID via Disk Utility because 1 disk was not available (They're identical and always appear as only 1 in System Profiler and this is misleading).
I as able to enable the second one and now rebuilding the RAID set and purchasing Firewire external hard disk hoping it will be better. USB is atrouble if not connected directly to the Mac.
Thank you very much for interesting in my problem.
Simon

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Answer 3

Mar 9, 2010 7:06 AM in response to majortom67

RAID 0 doesn't permit for a "degraded" state. RAID 1 does, perhaps that is what you have.

In RAID 0, data is spread evenly across two disks without parity (error checking) or duplication. If one of the disks experiences a fault, all data on the RAID is lost. The idea of RAID 0 is that you are sacrificing the integrity of the data for speed.

RAID 1 mirrors the disks, so one is always a replica of the other. It has a degraded state where 1 drive has a fault, and the fail-over condition is that the RAID switches to using a single disk (until the defective drive is replaced).

RAID 0 has no repair options.

RAID 1 has a single repair option: to replace the defective drive with one of equal or higher capacity.

Other than replace the faulty drive, there's really nothing you need to do. The RAID software should take care of the rest.

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Answer 4

The hatter

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Mar 9, 2010 7:11 AM in response to majortom67

USB with its high cpu overhead, and very slow I/O is a horrible interface to start with (at least until USB 3 is out) and more than half as slow as the native speed of any single drive today.

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Answer 5

majortom67 Author

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Mar 9, 2010 7:12 AM in response to J D McIninch

Here it is:

http://img709.imageshack.us/img709/5944/degradedmirroru.png

Message was edited by: majortom67

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Answer 6

The hatter

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Mar 9, 2010 7:23 AM in response to majortom67

So you tried to setup three partitions on those two 500GB drives. And do it over USB, and wondering why it is having trouble?

Any RAID, mirror or otherwise, should be backed up.

Delete what you have and use as single drives and just clone the primary data to the other... as needed for proper backup.

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Answer 7

majortom67 Author

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Mar 9, 2010 7:44 AM in response to The hatter

The next step is trying to do it on firewire boxes. If problems still appear I'll do what you said (I'm also thinking about it since long time...).
Regards.
Simon

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Answer 8

mickey13

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Mar 9, 2010 7:47 AM in response to majortom67

I've only seen that when a drive in the array was malfunctioning or had a loose connection.

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Answer 9

The hatter

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Mar 9, 2010 8:02 AM in response to majortom67

USB2 = less than 40MB/sec, and without adding PCI Express or something, there is only one bus/channel shared by all USB devices.

A non-RAID will run faster and better.

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Answer 10

majortom67 Author

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Mar 9, 2010 8:25 AM in response to The hatter

Thank you for your advices but if I needed speed I already would have FW800 boxes. FW400 or USB2 speed is enough.
Simon

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Answer 11

Mar 9, 2010 8:36 AM in response to majortom67

Hi majortom67;

What is your reason for using a RAID0 array? Exactly what do you hope to gain with it?

It certainly doesn't sound from the way you are going about implementing it that this is the correct solution so I would like to know what problem you are solving here.

Allan

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Answer 12

The hatter

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Mar 9, 2010 8:52 AM in response to majortom67

You are killing your USB ports and other devices. You aren't getting anything, and your mirror isn't cutting it (and made more complex by having three volumes).

Sounds like you also have too many 'boxes' - again, there is one FireWire bus, and one USB.

Putting two drives on one, daisy-chaining, etc.

Even Mac Pro with independent controllers and the rest wouldn't do what you attempting, and USB/eSATA or quad-interface have their problems.

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Answer 13

majortom67 Author

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Mar 9, 2010 9:51 AM in response to Allan Eckert

Please... what is the purpose of a mirrored drive?

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Answer 14

majortom67 Author

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Mar 9, 2010 9:52 AM in response to The hatter

You mean RAID is prolematic also with deidcated hardware?

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Answer 15

Mar 9, 2010 10:28 AM in response to majortom67

RAID-0 isn't mirrored. That'd be RAID-1. You'd use RAID-0 for performance, with the understanding that RAID-0 jeopardizes the data (if either drive fails, all of the data is lost). RAID-1 you'd use to increase your chances of recovery, if one drive fails, the other drive is an exact duplicate; if the RAID controller fails, the drive can be moved to a new one and be expected to work.

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