Strip size question

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.
Thornton

Strip size question

Post by Thornton » Sun Aug 23, 2009 8:32 pm

Hey everyone

A quick question:

I have had very mixed results when trying to recover my Raid 5 so i have a few questions to help narrowing my options. Im pretty sure i know the answers, but i want to be sure.

1: If i set the stripe size wrong, R-studio will NEVER be able to recover a file correctly unless the file i smaller that the stripe size? Right?
2: If a file is larger than the stripe size it will NEVER recover correctly unless the drive order and block order is correct? Right?

If the above is correct can i use it to conclude the following:
1: I have set stripe to 128Kb and have successfully recovered a picture with size of 180kb -> Stripe is definetly 128kb AND at least 2 disks are in the correct order (for the selected block order) or have i completely misunderstood something?
2: With stripe still 128Kb i have recovered a picture of size 300Kb corretly -> Stripe is still correct AND at least 3 disks are in the correct order (for the selected block order)


Regards
Thornton.

Alt
Site Moderator
Posts: 2271
Joined: Tue Nov 11, 2008 2:13 pm
Contact:

Re: Strip size question

Post by Alt » Mon Aug 24, 2009 4:03 am

Thornton wrote: 1: If i set the stripe size wrong, R-studio will NEVER be able to recover a file correctly unless the file i smaller that the stripe size? Right?
2: If a file is larger than the stripe size it will NEVER recover correctly unless the drive order and block order is correct? Right?
1. Yes,
2. Depends. Generally yes, but there may be cases when it can be recovered (see below).
To be sure, the file size should be larger than (block size)*((number of disks) - (number of disks with parity))
Thornton wrote: If the above is correct can i use it to conclude the following:
1: I have set stripe to 128Kb and have successfully recovered a picture with size of 180kb -> Stripe is definetly 128kb AND at least 2 disks are in the correct order (for the selected block order) or have i completely misunderstood something?
2: With stripe still 128Kb i have recovered a picture of size 300Kb corretly -> Stripe is still correct AND at least 3 disks are in the correct order (for the selected block order)
You have a correct stripe (block) size and stripe (block) sequence for
1. Two disks
3. Three disks
Why I'm not saying "correct disk order"? Because there are two factors affecting the stripe sequence: disk order and block order. So there may be cases that you have a correct stripe sequence but wrong disk and block order.
And don't forget, there are such thing as an offset.
Maybe this link will help you:
http://www.data-recovery-software.net/A ... ndex.shtml

Thornton

Re: Strip size question

Post by Thornton » Mon Aug 24, 2009 6:25 am

Hey Alt

Thank you for the reply.
I am aware of the disk order vs. block order so ill keep trying.

Unfortunately the article doesn't help me much since the Raid controller thought i would be wise to do an initialize of the raid!! - i did stop i rather quick, but not quick enough so the first 500 sectors or so on all disks are just zeroes :-(

Alt
Site Moderator
Posts: 2271
Joined: Tue Nov 11, 2008 2:13 pm
Contact:

Re: Strip size question

Post by Alt » Mon Aug 24, 2009 10:06 am

Thornton wrote: Unfortunately the article doesn't help me much since the Raid controller thought i would be wise to do an initialize of the raid!! - i did stop i rather quick, but not quick enough so the first 500 sectors or so on all disks are just zeroes :-(
Maybe, this is an offset? And the boot sector lies further? I would try to find this out.

Post Reply