Rebuilding RAID from Apple MacPro Classic 4.1 Hardware RAID-5 (4 drives)

Discussions on using the professional data recovery program R-STUDIO for RAID re-construction, NAS recovery, and recovery of various disk and volume managers: Windows storage spaces, Apple volumes, and Linux Logical Volume Manager.
winguru
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Joined: Thu Apr 25, 2019 3:48 pm

Rebuilding RAID from Apple MacPro Classic 4.1 Hardware RAID-5 (4 drives)

Post by winguru » Thu Apr 25, 2019 4:27 pm

Greetings,

I am attempting to rebuild my RAID-5 environment from my Apple MacPro Classic. I have four (4) 2 TB drives in a hardware RAID-5 configuration. I accidentally pulled the wrong drive when investigating a soft-failure on another drive, so I ended up taking the whole array offline. Long story short, Apple does not provide the ability to recover from this situation, so I am using this software in an attempt to rebuild a working RAID environment.

All of my drives are connected to another PC and are responding properly, however I am having issues trying to properly detect my RAID parameters and/or get this software to properly use my custom RAID configuration.

Based upon my research and experimentation, it seems that the Apple RAID card uses a 3 block parity group, rather than the traditional 4 block for traditional RAID-5 arrays. This means that the parity block gets shifted each row (as one would expect), but also that the first row has two parity blocks.

The following table shows the expected RAID-5 layout:
[ P ] [ 1 ] [ 2 ] [ P ]
[ 3 ] [ 4 ] [ P ] [ 5 ]
[ 6 ] [ P ] [ 7 ] [ 8 ]

Notice that the layout is similar to a Right-Synchronous RAID-5 layout, but there are only two data blocks per sequence rather than three.

I've created a custom RAID layout and while it seems to partially work, performing a RAID consistency check shows 1/5 (20%) of the blocks as being "not checked." I don't know if this is an artifact of the weird RAID-5 layout, but it partially confounding my recovery efforts.

For reference, I've attached the custom RAID-5 definition with no parity delay. I have created other, more complex layouts with increasing parity delays, but I'll keep it simple here for now...

Any advice or recommendations would be greatly appreciated...

Thanks in advance!
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Alt
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Re: Rebuilding RAID from Apple MacPro Classic 4.1 Hardware RAID-5 (4 drives)

Post by Alt » Fri Apr 26, 2019 12:41 pm

We have a correct RAID description file in our help: Advanced RAID 5 (The second one on the page.) The offset though may be different.

winguru
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Re: Rebuilding RAID from Apple MacPro Classic 4.1 Hardware RAID-5 (4 drives)

Post by winguru » Fri Apr 26, 2019 10:27 pm

Yes, thank you for that reference. That (among others) is what I was going on and one of the reasons I purchased your software.

My issue seems to be (at least partly) that when I try to check my RAID consistency, 1/5 of the blocks are marked as "not checked".

I'll include some screenshots if that helps illustrate the issue...

This is the RAID configuration:
RAID Configuration.png

And this is the (partial) example of one of my RAID Consistency checks:
RAID Consistency Check.png
Thanks!

P.S. To preempt any questions about if I made the RAID incorrectly:
  • The first three lines in the "RAID Sequence" box (A1 B1 C1 D1, etc.) are non-removable. They are not present in the XML definition though, so I don't know if they are affecting the RAID or not. But I've tried everything to clear/remove them and they always seem to be present in any custom RAID format.
  • The "Block order for" shows RAID-0. I usually set it for Custom, but this screenshot shows the default. And even though I set it as Custom, it seems to reset back to RAID-0 whenever I load my saved preset.
  • The screenshot shows that RAID changes are pending. Again I normally apply the changes, I had just loaded one of my presets before I took the screenshot and that's why it shows it has changed.
  • If you notice closely, the RAID Consistency Check shows a block size of 512 Sectors per block. This was a result from another blocksize test than the 512K test showed in the RAID Configuration screen. But in all cases, 1/5 of the blocks show as "not checked". The only difference is the blocksize.
  • Lastly, yes I know there are a lot of red (bad checksum) blocks. I've gotten different patterns of good blocks, up to about 50% good/bad percentage. And yes, I can see the HFS+ structure in some cases. But I get the same partial results with some RAID-5 and even RAID-4 configurations, so I'm not convinced that my custom RAID configuration is being properly utilized.
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winguru
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Re: Rebuilding RAID from Apple MacPro Classic 4.1 Hardware RAID-5 (4 drives)

Post by winguru » Sat Apr 27, 2019 8:53 am

To hopefully clarify, I looked more closely and I believe I misspoke when I said 1/5 (20%) of the blocks were "not checked". As the following screenshot shows, there are 12 checked blocks followed by 4 unchecked blocks. That's 16 total in a sequence and 4/16 or 1/4 (25%) are not checked, not 20%.

RAID Consistency Check - 2.png
Thanks!
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Alt
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Re: Rebuilding RAID from Apple MacPro Classic 4.1 Hardware RAID-5 (4 drives)

Post by Alt » Sat Apr 27, 2019 12:20 pm

Did R-Studio throw error messages that it couldn't read some disk sectors?

winguru
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Re: Rebuilding RAID from Apple MacPro Classic 4.1 Hardware RAID-5 (4 drives)

Post by winguru » Sat Apr 27, 2019 12:44 pm

No, there were no errors or warnings about unreadable sectors.

If I pick the built-in RAID-5 Right Symmetric configuration, this is what I see for the RAID Consistency Check:
RAID Consistency Check - 3.png
Thanks!
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Alt
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Re: Rebuilding RAID from Apple MacPro Classic 4.1 Hardware RAID-5 (4 drives)

Post by Alt » Sun Apr 28, 2019 1:20 pm

Have you tried our RAID description file? Because I see some wrong sequences on your second screenshot. There should be no 4-element sequences.

winguru
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Re: Rebuilding RAID from Apple MacPro Classic 4.1 Hardware RAID-5 (4 drives)

Post by winguru » Sun Apr 28, 2019 2:16 pm

I have looked over the exported configuration of the custom RAID-5 configuration I made (as per your advanced RAID configuration guidance). I included my exported XML file as an attachment to my first message.

The key components of that file are as follows:
<Table>
<Block id="A1" sequence="1">XorOfData</Block>
<Block id="B1">1</Block>
<Block id="C1">2</Block>
<Block id="D1" sequence="2">XorOfData</Block>
<Block id="A2">3</Block>
<Block id="B2">4</Block>
<Block id="C2" sequence="3">XorOfData</Block>
<Block id="D2">5</Block>
<Block id="A3">6</Block>
<Block id="B3" sequence="4">XorOfData</Block>
<Block id="C3">7</Block>
<Block id="D3">8</Block>
</Table>
<Sequences>
<Sequence id="1">A1 B1 C1</Sequence>
<Sequence id="2">D1 A2 B2</Sequence>
<Sequence id="3">C2 D2 A3</Sequence>
<Sequence id="4">B3 C3 D3</Sequence>
</Sequences>

There are no 4 element sequences in that definition file. Nonetheless, when I load that file or create a new custom configuration, there are always 4 element segments that are at the beginning of the RAID sequence window, and they don't seem to be able to be removed. The number of these initial sequences is always the same number as the "number of rows".

Again, I'm not sure if that's intentional or not, but I've not been able to remove them regardless of how I've tried.

Hopefully the following GIF animation helps to demonstrate this behavior:
R-Studio RAID Configuration Actions.gif
Thanks!
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winguru
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Re: Rebuilding RAID from Apple MacPro Classic 4.1 Hardware RAID-5 (4 drives)

Post by winguru » Mon Apr 29, 2019 9:52 am

For what it's worth, I'll also share the code I wrote to create custom RAID-5 definitions for different parity delays. It doesn't generate the complete XML file, just the "table" and "sequences" sections that define the stripe pattern.

https://repl.it/@winguru/R-Studio-Apple ... -Generator

Comments and/or suggestions are welcome.

Thanks!

Alt
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Re: Rebuilding RAID from Apple MacPro Classic 4.1 Hardware RAID-5 (4 drives)

Post by Alt » Fri May 03, 2019 10:53 am

Right now we're investigating this problem.

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