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The_Great_Sephiroth
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PostPosted: Mon Nov 07, 2016 7:46 pm    Post subject: Intel X99 FakeRAID support? Reply with quote

I am installing Windows 7 Professional onto a high-end gaming rig with the X99 chipset. It has two 1TB disks in RAID1. Windows sees this out of the box. After the initial install, I use System Rescue CD to image the system. This is Gentoo-based, so I am hoping I can get some help. I see /dev/mapper/isw_xyz_Primary. If I open that in parted or fdisk, I see three partitions. They're the same name, only with "-part1", "-part2" or "-part3" on the end. However, I cannot mount them as they do not exist under /dev/mapper. What do I do?
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NeddySeagoon
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PostPosted: Mon Nov 07, 2016 10:43 pm    Post subject: Reply with quote

The_Great_Sephiroth,

Is this a case of Windows Dynamic Discs?
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The_Great_Sephiroth
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PostPosted: Tue Nov 08, 2016 3:07 am    Post subject: Reply with quote

No, this array was created with the UEFI RAID utility by Intel. It displays as "/dev/mapper/isw_ccjebgag_Primary", which is a link back to "/dev/dm-0".
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NeddySeagoon
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PostPosted: Tue Nov 08, 2016 11:24 am    Post subject: Reply with quote

The_Great_Sephiroth,

/dev/dm-0 is a single logical volume to Linux. That you have partitioned it would be an odd thing to do.
There are several ways to mount the filesystems it contains.

Use mount with the offset=X option, where X is the number of bytes from the start of /dev/dm-0 to the start of the partition.
In effect, you interpret the starts from the partition table for yourself.

You may be able to get at the partitions with losetup - see the man page.
If that works /dev/loop0-p1 and friends will be the partitions holding the filesystems that you can mount.
There is one wrinkle to using losetup this way. I think it only works with MSDOS partition tables,
If you only get /dev/loop0-p1 and no entries for -p2 and -p3 this is what has happened and its not going to work for you.
Its back to mount with -o offset=
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The_Great_Sephiroth
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PostPosted: Tue Nov 08, 2016 1:35 pm    Post subject: Reply with quote

I can pass the offsets with ease. The partition table is GPT since the system is UEFI (no old BIOS support) so I will try that. Should that fail, I am currently building a live Windows 7 DVD with utilities on it. Think MiniXP, but Mini7 instead. It fits on a DVD and is a fully-functional live OS I use for working on Windows systems. I know it will work. I had to rebuild it to add USB3 support. My current one does not have USB3 built into the DVD, and this system only has 3.0 ports.

Thanks for the help, Neddy!
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PostPosted: Tue Nov 08, 2016 3:25 pm    Post subject: Reply with quote

The_Great_Sephiroth,

If losetup understands GPT, thats the easiest. If not, oftsets aren't hand.
I'm curious to know what losetup does.
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The_Great_Sephiroth
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PostPosted: Thu Nov 10, 2016 2:53 pm    Post subject: Reply with quote

I haven't messed with it, YET. I finished my latest live Windows 7 DVD and did my work with it, but once the system has been syspreped, I will need to use Linux to image it. I normally image the first 512 bytes, then the next 2047 sectors at 512b each to clone any hidden info, then the individual partitions. I clone with "dd if=/dev/sdx bs=4M | xz -T 0 > /mnt/backup/sdx.xz". Works great!
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PostPosted: Thu Nov 10, 2016 3:45 pm    Post subject: Reply with quote

The_Great_Sephiroth,

With a GPT partition tables that's not enough. The first 512 bytes, then the next 2047 sectors at 512b each gets you the MPR and the primary copy of the partition table.
However, GPT keeps another copy of the partition table outside of any filesystem at the end of the drive too.
It gets unhappy if the two don't match.
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The_Great_Sephiroth
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PostPosted: Sun Nov 13, 2016 3:28 pm    Post subject: Reply with quote

Yes, I know. I accidentally gave my method for backing up MSDOS partitioned disks, not GPT. My bad!

On that note, I am not sure how to use losetup with the array. I finished the system and have zeroed the free space, and now need to image it, but am not sure how. Both fdisk AND parted can see the partitions, but I cannot mount them. To complicate matters, it shows the partition offsets, but is that in 512b logical or 4096b physical sectors? Confusing as heck. I don't understand how every tool on the planet can see my partitions but there is no simple way to mount them.

*UPDATE*

Screenshot
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szatox
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PostPosted: Sun Nov 13, 2016 6:05 pm    Post subject: Reply with quote

I'm pretty sure It's in 521b logical sectors. The first partition usually starts at 1M, which is referred to as 2048 chunks.
Use losetup -o <offset bytes> <raw device image> to bind it to loop and then simply mount that loop just like any other device.
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PostPosted: Sun Nov 13, 2016 8:09 pm    Post subject: Reply with quote

Well I went ahead and imaged the entire thing (/dev/mapper/isw*) with dd piped to xz and it worked. Once I test my deployment and get it right, I'll try imaging that way. The thing is, I believe the MBR for a GPT changes size, so I am not sure what to do there.
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PostPosted: Sun Nov 13, 2016 11:53 pm    Post subject: Reply with quote

The_Great_Sephiroth,

The MBR is 512b. its not linked to the partition table type.
With GPT, you get a 'protective' MSDOS partition table in the MBR for free anyway.
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PostPosted: Tue Nov 15, 2016 9:42 pm    Post subject: Reply with quote

That is what I thought. It would make a 512b MBR which says the entire disk is one giant GPT partition, and the GPT partition data is somewhere at the start of the big GPT partition. I have read many times though, that the table changes size with the number of partitions in that GPT area. Is this correct? How is GPT laid out on disk? I'd like to have a better backup policy. Also, thanks for all of the help. I do love learning new things in Linux. Now if we could only get rid of systemd! Well, make it optional.
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