Safety of accessing Apple Software RAID under Windows XP/Ubuntu
I've got 2 500GB external USB drives that I've RAIDed together to form a mirrored 500gb drive. I use this to store most of my important documents, along with movies, photos and music. I also use this drive for my Time Machine backups. These disks use the GPT partitioning scheme.
I have Windows XP and Ubuntu installed on my machine along side Mac OS X. Under XP I have MacDrive installed so that I can read/write to any HFS+ partition. I also have an ext3 driver installed under XP so I can read/write to my Ubuntu partition.
Under XP: Unfortunately, since my external drives are partitioned using the GPT scheme, Windows XP only recognizes them as EFI protective disks, and hence MacDrive cannot read/write to the HFS+ RAID volumes.
Under Ubuntu: Both of the RAID volumes mount as read only, which is fine for me. This works because Ubuntu can read the GPT table.
My solution: Apple's bootcamp utility creates a GPT/MBR hybrid by mirroring the contents of the GPT to the MBR. My solution was to modify the MBR of one of my RAID disks so that it mirrors the GPT:
fdisk /dev/disk2
Disk: /dev/disk2 geometry: 60801/255/63 [976773168 sectors]
Signature: 0xAA55
Starting Ending
#: id cyl hd sec - cyl hd sec [ start - size]
------------------------------------------------------------------------
1: EE 0 0 2 - 1023 254 63 [ 1 409639] <Unknown ID>
2: AF 1023 254 63 - 1023 254 63 [ 409640 976101344] HFS+
gpt -r show disk2
gpt show: disk2: Suspicious MBR at sector 0
start size index contents
0 1 MBR
1 1 Pri GPT header
2 32 Pri GPT table
34 6
40 409600 1 GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
409640 976101344 2 GPT part - 52414944-0000-11AA-AA11-00306543ECAC
976510984 262144 3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
976773128 7
976773135 32 Sec GPT table
976773167 1 Sec GPT header
As you can see, I made a new entry in the MBR to mirror the Apple RAID partition (index 2) in the GPT. And it "works". Windows XP's Disk Management console shows the disk as having 2 partitions, and MacDrive mounts, and reads the HFS+/RAID partition.
But my question is... How safe is this? If I write to the RAID partition under XP or Ubuntu (if i mount the drive as r/w), will the RAID set be rebuilt automatically under OS X, or will the modifications go unnoticed? How does Apples software RAID detect modifications to the disk? Does it checksum the HFS+ directory and compare them at mount time?
Thanks,
Adam
I have Windows XP and Ubuntu installed on my machine along side Mac OS X. Under XP I have MacDrive installed so that I can read/write to any HFS+ partition. I also have an ext3 driver installed under XP so I can read/write to my Ubuntu partition.
Under XP: Unfortunately, since my external drives are partitioned using the GPT scheme, Windows XP only recognizes them as EFI protective disks, and hence MacDrive cannot read/write to the HFS+ RAID volumes.
Under Ubuntu: Both of the RAID volumes mount as read only, which is fine for me. This works because Ubuntu can read the GPT table.
My solution: Apple's bootcamp utility creates a GPT/MBR hybrid by mirroring the contents of the GPT to the MBR. My solution was to modify the MBR of one of my RAID disks so that it mirrors the GPT:
fdisk /dev/disk2
Disk: /dev/disk2 geometry: 60801/255/63 [976773168 sectors]
Signature: 0xAA55
Starting Ending
#: id cyl hd sec - cyl hd sec [ start - size]
------------------------------------------------------------------------
1: EE 0 0 2 - 1023 254 63 [ 1 409639] <Unknown ID>
2: AF 1023 254 63 - 1023 254 63 [ 409640 976101344] HFS+
gpt -r show disk2
gpt show: disk2: Suspicious MBR at sector 0
start size index contents
0 1 MBR
1 1 Pri GPT header
2 32 Pri GPT table
34 6
40 409600 1 GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
409640 976101344 2 GPT part - 52414944-0000-11AA-AA11-00306543ECAC
976510984 262144 3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
976773128 7
976773135 32 Sec GPT table
976773167 1 Sec GPT header
As you can see, I made a new entry in the MBR to mirror the Apple RAID partition (index 2) in the GPT. And it "works". Windows XP's Disk Management console shows the disk as having 2 partitions, and MacDrive mounts, and reads the HFS+/RAID partition.
But my question is... How safe is this? If I write to the RAID partition under XP or Ubuntu (if i mount the drive as r/w), will the RAID set be rebuilt automatically under OS X, or will the modifications go unnoticed? How does Apples software RAID detect modifications to the disk? Does it checksum the HFS+ directory and compare them at mount time?
Thanks,
Adam
iMac, Mac OS X (10.5.5)