| brent timothy saner on 17 Mar 2015 00:55:55 -0700 |
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| Re: [PLUG] Writing to Windows 7 software RAID volumes |
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 On 03/16/2015 10:56 PM, Josh Zenker wrote: > I have a pair of disks mirrored using the software RAID implementation > built into Windows 7. Ideally I would like to be able to mount them > read-write from the Linux side, but I'm afraid of corrupting the dynamic > disk. The general consensus on the Ubuntu Forums is that it's a bad > idea. (I have been mounting them read-only without issues.) Still, I'm > wondering if anyone here has tried it. > > JZ Little-known fact, md (and mdadm, etc.) can work with windows software raid as they use compatible superblocks (at least, they did in windows XP- haven't tested on Win7 but I can't imagine this changing). There are two ways- the dmraid way (easy) and the mdadm way (more difficult). Both are definitely easy compared to what you thought may have been the case, however. Try the dmraid way first- if it reports no found RAID devices, then continue to the mdadm way. dmraid is designed to work with "fakeraid"- e.g. motherboard-assisted software RAID (I guess this technically would be "firmware RAID" since it's neither hwraid nor swraid). I have included both methods just in case Win7 makes some hooks into the motherboard for determining how a RAID should be assembled. Make sure you make backups first. As always. This has worked before, but as I said, untested in Win7. EASY WAY (dmraid): Install dmraid if it isn't already installed. Then: dmraid -r This will list any devices found that can be assembled. If it finds devices, great! You have your work cut out for you. You can run: dmraid -ay And they'll automatically be assembled. It should assign a name to the array (for instance, WIN_RAID) and then should be accessible via /dev/mapper (e.g. /dev/mapper/WIN_RAID). You can then mount it as a normal NTFS volume (read or, if your driverset/modules support it, write as well): mount -t ntfs /dev/mapper/WIN_RAID /mnt/WINDOWS If it *doesn't* find any devices it can assemble into a RAID, well.... read on. HARD WAY (mdadm): Install mdadm if it isn't already installed. Let the following be representative: N=some unused number for an array in /dev/md*. X=RAID level in your windows array- 0 for RAID0, 1 for RAID1, etc. Y=number of disks in the array Z[0-9]=hardware devices in the windows array A=partition number of Z[0-9] that houses the RAIDed partition WARNING: Do ****not*** use ---create in mdadm. I'll say it again: DO NOT USE - --create IN MDADM FOR WINDOWS ARRAYS. It will destroy the data on the drives, along with the existing superblocks. This is why we specify - --build- --assemble does not work, but --build does. USAGE: mdadm --build /dev/md*N* --chunk=64 --level=*X* --raid-devices=*Y* /dev/sd*Z1*A* /dev/sd*Z2*A* (whiout the *'s. repeat the last /dev/sdZ[0-9]'s for all devices/partitions in the array.) EXAMPLE: Let's say in Windows you have drive A, B, and C in a RAID5. They each have 2 partitions, with the second being the member of the RAID array. drive A in linux maps to /dev/sda drive B in linux maps to /dev/sdb drive C in linux maps to /dev/sdc You already have /dev/md0 present (for whatever reason), so you want to assemble into a new array- /dev/md1. mdadm \ --build /dev/md1 \ --chunk=64 \ --leevl=5 \ --raid-devices=3 \ /dev/sda2 \ /dev/sdb2 \ /dev/sdc2 Then, to mount, mount -t ntfs /dev/md1 /mnt/WINDOWS Make sure windows had a clean shutdown. Sometimes you'll get an error when you try to build the array- if that's the case, try futzing with the order of the drives as it does matter (but improper ordering shouldn't be destructive). watch cat /proc/mdstat is useful for watching the progress of the build. You should be able to mount and write to it safely while (re)buildiing, but just don't shutdown or (goodness.) power off before it finishes rebuilding. If you've written to the array while it's (re)building, for good measure I'd do a sync(1) as soon as it finishes (re)building but that probably isn't necessary. Hope this helps. Please report back with results. FURTHER READING: http://superuser.com/questions/694050/how-to-create-a-software-raid-1-array-on-windows-7-not-spanning-whole-disks https://help.ubuntu.com/community/FakeRaidHowto http://www.chrysocome.net/virtualvolumes http://ubuntuforums.org/showthread.php?t=833653&page=4 -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQIcBAEBCgAGBQJVB932AAoJEIwATC+TSB9rj4gP/1JZ1Q4XQLATJ0cO+jsfUwVx B0SV26WVWhCvzrZk2kKFQeZjnxm2TlwoiSY1KWD0tyecjmCPnRd/9YAalgoLNAmn pHJjEowON1xGB9cn9f1wEV+sddfmBFP7JaFvAWDRKvBefsdhozc88OmQVaWaoCFI C2DyprAtb3uszYpnA61hZv1qzXJjwlOVPx1zVnlJ9myLM3Oh8hEBT4l3sVDgQkrf xBA/ceY4mOv4aKMwA6RRWfO7OkYpOKcd9K/GfsjAtw8WcwMyW3dXwH+QyH0CL6P5 aib1q8HfpjeQR3aG+1I6Ud3QsnFMGF4yzGizLqoeoA3RjCwIcTdqH1DlhfT3dhe0 Wh2S31ZbjDujJj/esklVjKXEmo0QNFcbhzGTllAvUWOVHvLdVYgLJtbYANj+r3Hc VdI/1dwVyxL5Df30R0svnsY3Il39Fk3R9OgdOdvYeb0x8mnmQQrLl3cgoFZJiwWH M9d1F19LSFt0/6XAuaKfaISldQT4+jTMzVrB0VFvZfMZqunfgNwBsFaLjtyu3I4+ vktInnaXmiz1wvdlBRVJBVORdTY/hLze1QmcDR7j8iN1yE3CnB5v+wrvF6gtADuZ iDEczP/gucCRTe/HLlDPnWFya+7x03WVd/5Cpsu/pLb7RTvT4g2gpIvIuotKfIRo f8YlbOvHQAwYSMQFv1Nf =WzwK -----END PGP SIGNATURE----- ___________________________________________________________________________ Philadelphia Linux Users Group -- http://www.phillylinux.org Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce General Discussion -- http://lists.phillylinux.org/mailman/listinfo/plug