A friend of mine bought a new 1TB hard drive from Samsung (HD103SJ with firmware 1AJ100E4). He used Windows Vista to partition it and format 2 partitions for NTFS, one to install Windows 7 and one to move data from an external drive. Everything worked well, Vista used the drive as intended. When he rebooted to install Win7 everything – Windows 7 setup, BIOS and unfortunately also Vista – saw the drive with only 33 MB capacity, reporting one unformatted partition on it.
Searching the internet we found out it must be a problem with the drive’s host protected area (HPA) in conjunction with his mainboard/SATA controller (ironically from Gigabyte). He updated BIOS and chipset drivers but the problem persisted. According to some forums there are some tools for Windows to fix that issue. Since many people reported data loss afterwards and he didn’t have another copy of the data he moved from his external drive we decided to boot into the new Gentoo Live DVD that also allowed me to log in remotely via SSH to investigate the problem (we are more than 500km away from each other).
Following a short guide on how to detect and disable HPA we could see the settings of his drive:
# hdparm -N /dev/sdb
/dev/sdb:
max sectors = 65134/1953525168, HPA is enabled
This seems to have been the opposite configuration of what should have been set according to the guide: While the examples from the guide had a much greater value before the slash his drive seemed to show the intended remainder to be allocated to the HPA set for “public” use, so his HPA seemed to cover almost the entire 1TB of his HDD.
Before we tried to correct that value we wanted to check if we can access any data right away. Unfortunately everything prevented us from accessing the HPA – the kernel did only register /dev/sdb1 but not /dev/sdb2, smartmontools showed 33MB capacity as well, parted refused to work and fdisk finally showed the correct partition table but reported a mismatch in geometry, so at least we still seemed to access the same start sector of his HDD:
Disk /dev/sdb: 33 MB, 33348608 bytes
255 heads, 63 sectors/track, 4 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x24c2a85c
Device Boot Start End Blocks Id System
/dev/sdb1 1 38245 307200000 7 HPFS/NTFS
Partition 1 has different physical/logical endings:
phys=(1023, 254, 63) logical=(38244, 193, 29)
/dev/sdb2 38245 121601 669558784 7 HPFS/NTFS
Partition 2 has different physical/logical beginnings (non-Linux?):
phys=(1023, 254, 63) logical=(38244, 193, 30)
Partition 2 has different physical/logical endings:
phys=(1023, 254, 63) logical=(121600, 247, 55)
We also tried to access /dev/sdb with dd but only got the 33MB until the drive “ended”. Considering the HPA modifications to be the last resort we tried to change it only temporarily at first, but had to set it permanently to get any effects on the system after a reboot. Please note that the manpage for hdparm explicitely states that changing that setting is “VERY DANGEROUS, DATA LOSS IS EXTREMELY LIKELY”. I copied the old value to a text editor before making the modifications, so I hoped we could at least set it back to what it was before our changes in case it didn’t work well. To make a permanent change, simply run the same command with p (for permanent) followed by the new maximum value to be set (to disable HPA this would be the exact same value as written after the slash):
# hdparm -N p1953525168 /dev/sdb
Having rebooted, fdisk did not complain any more and the kernel recognized both partitions:
Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x24c2a85c
Device Boot Start End Blocks Id System
/dev/sdb1 1 38245 307200000 7 HPFS/NTFS
/dev/sdb2 38245 121601 669558784 7 HPFS/NTFS
hdparm confirmed that we just disabled HPA:
# hdparm -N /dev/sdb
/dev/sdb:
max sectors = 1953525168/1953525168, HPA is disabled
We mounted his data partition read-only using ntfs-3g and since everything seemed fine we started to copy everything back to his external drive, just to be sure we had a backup of his data in case that Windows would decide to crash his partition after another reboot. However, Windows Vista did recognize the drive correctly again and so did Windows 7; he can access all data and nothing seems to be corrupted or missing.
It appears strange that Windows initially ignored the HPA and worked well until he rebooted. But having had extreme, sporadic problems myself using a Silicon Image SATA controller with Windows XP SP2 as well as Windows Vista (without SP, back in 2007) it did not really surprise me any more.