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w.simon
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Drobo 5D / DRDR5-A / PN : 917-00001-001

Sat Jul 11, 2015 8:11 am

Hello

I got a Drobo 5D populated with 5 x 3TB HDD. (DAS)

I seems that beyon raid are pain to recover, but seems that on this units with all HDD used to be the same size, it should be a RAID5.

Does someone come over this type of case and can give me a light or idea, like raid parameters

Thanks
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hddguy
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Re: Drobo 5D / DRDR5-A / PN : 917-00001-001

Mon Jul 13, 2015 4:24 am

I know of only 3 people who say they can solve these without the unit, but have never had one built without the original housing. For me I have always required the unit. If the unit is faulty, its possible that the unit can be repaired, alternatively the disks can be entered into a donor unit of same model and FW revision as metdata is stored on the disks - also the reason why the order you place the disks in does not matter. In a few other situations I was able to access the data by putting the unit into a Read Only mode and in this data was visible.

What is the cause of data loss?

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w.simon
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Re: Drobo 5D / DRDR5-A / PN : 917-00001-001

Mon Jul 13, 2015 6:28 am

Hello

This unit was on a Windows PC, plugged on a mac and formated to HFS+ (16Tb partition is visible when you put 5*3TB drive in the unit ... Strange)
Looked with winhex all the 16TB is full with 00

Checking the disque one by one :

Drive are not full of 00
Scanning the disk gives you some NTFS file structure, with jpeg that are off course corrupted

The information i found about drobo :

http://arstechnica.com/business/2011/03 ... eview-1/1/
VS
http://www.reclaime.com/library/drobo-recovery.aspx

Entropy Analysis gives nothing, and parity tests too so...

I think customer with shelve it ...
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lcoughey
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Re: Drobo 5D / DRDR5-A / PN : 917-00001-001

Mon Jul 13, 2015 1:07 pm

The problem with Drobo and the likes is that they are selling themselves to users who cannot afford to buy a real server. So, the users are unable to afford the cost of a recovery from proprietary RAID configurations used. Basically, not worth looking at most of the time.

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Re: Drobo 5D / DRDR5-A / PN : 917-00001-001

Mon Jul 13, 2015 1:08 pm

I find the explanation about the "RAID" of Drobo being at a file level rather than a block level to be very interesting... by that logic then most files could theoretically be recovered off individual disks in RAW.... I've never actually had a Drobo come in, maybe I'll have to buy one just to study how it actually writes data.

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Re: Drobo 5D / DRDR5-A / PN : 917-00001-001

Mon Jul 13, 2015 2:15 pm

Yep, they are correct about that. Apparently each file is assigned an "Object #" then each object # is assigned storage blocks. And it's all tracked by a couple of filesystem aware tables.

Here's their patent for anyone who want's to read it: http://www.file-medics.com:4000/fbsharing/iH3aTZmc
Page 2 pretty nicely explains how it tracks everything.

So just to recover one file you'd need to learn how to understand both tables and track down the physical blocks needed, then piece them back together. Hmm.... maybe I should hire a programmer to write some Drobo data recovery software to automate this process.

hddguy
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Re: Drobo 5D / DRDR5-A / PN : 917-00001-001

Tue Jul 14, 2015 6:42 am

for the last case I looked at there seemed to be blocks of metadata every 4472000 (ish) bytes, understanding this metadata and probably creating some tool or script would be needed to decipher it and allow building of the RAID.

Also, analyzing the disks outside of the unit does somehow show different data than when in the unit, in some situations it appears as '00' when in actual fact there is data present.

Did you try to put unit to read only mode then mount with recovery software like r-studio?

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