BLKBSZSET still not working on 2.4.18 ?
Hi !
I'm trying to backup a partition on an IDE drive which has an odd number of sectors (204939). With a stock open/read you cannot access the last sector, and that why I tried the BLKBSZSET ioctl to set the basic read block size to 512 bytes. I verified the writen value with BLKBSZGET ioctl, but I still cannot read this last sector !
I've tried also this:
- FreeBSD : works but it don't want to port all my software to it
- raw devices: can't read the last sector:
# raw /dev/raw1 /dev/hda2 # dd if=/dev/raw1 of=C bs=512 dd: reading `/dev/raw1': No such device or address 204938+0 records in 204938+0 records out
What can it do ? Wait for a patch in 2.5.xxx ?
TIA,
Ludovic Drolez.
Quoted 5 lines · Ludovic Drolez
I'm trying to backup a partition on an IDE drive which has an odd number of sectors (204939). With a stock open/read you cannot access the last sector
What can I do ? Wait for a patch in 2.5.xxx ?
Hmm - I recall fixing this both for 2.4 and 2.5.
If that patch is not part of current 2.4, then probably this should be regarded as a known deficiency of 2.4. If I were to maintain a stable 2.4 I would not accept such changes.
You can test 2.5. If it is wrong there I must submit a patch.
Andries
Quoted 5 lines · Ludovic Drolez
I'm trying to backup a partition on an IDE drive which has an odd number of sectors (204939). With a stock open/read you cannot access the last sector, and that why I tried the BLKBSZSET ioctl to set the basic read block size to 512 bytes. I verified the writen value with BLKBSZGET ioctl, but I still cannot read this last sector !
Its a known 2.4 limitation. The last odd sector isnt normally used by anything so it has never been a big issue (except with EFI partition data). There is a patch to allow the last sector to be recovered but its quite ugly so never went mainstream.
Quoted 9 lines
Quoted 5 lines
I'm trying to backup a partition on an IDE drive which has an odd number of sectors (204939). With a stock open/read you cannot access the last sector, and that why I tried the BLKBSZSET ioctl to set the basic read block size to 512 bytes. I verified the writen value with BLKBSZGET ioctl, but I still cannot read this last sector !
Its a known 2.4 limitation. The last odd sector isnt normally used by anything so it has never been a big issue (except with EFI partition data).
Didn't some really obscure IBM drives use it for something internally, and shortly after everybody else had to stop using it incase they overwrote the custom data at the end of an IBM disk, or am I thinking of something else?
John.
Quoted 4 lines · John Bradford
Didn't some really obscure IBM drives use it for something internally, and shortly after everybody else had to stop using it incase they overwrote the custom data at the end of an IBM disk, or am I thinking of something else?
Something else - EFI uses the last sector for partitioning as one example. Drives do have protected private areas but they are shielded from normal use for obvious reasons
Quoted 9 lines · Alan Cox
Quoted 4 lines · John Bradford
Didn't some really obscure IBM drives use it for something internally, and shortly after everybody else had to stop using it incase they overwrote the custom data at the end of an IBM disk, or am I thinking of something else?
Something else - EFI uses the last sector for partitioning as one example. Drives do have protected private areas but they are shielded from normal use for obvious reasons
There is also a much older matter. In the distant past IBM used the last cylinder for testing. That means that many FDISK versions and many BIOSes subtract one from the number of available cylinders. There are several ways to ask the BIOS for the size of a disk, and some of these calls may invoke others, and then subtract one. I have seen disks that had lost three cylinders that way.
Andries
Quoted 2 lines · Andries Brouwer
You can test 2.5. If it is wrong there I must submit a patch. Andries
It seems to work perfectly with 2.5.56 even without using the BLKBSZSET ioctl.
But, I'm still reluctant to use an unstable kernel for backuping a partition. But maybe the 2.5 is stable enough to read blocks from IDE/SCSI drives, and send them over NFSv2 / IPv4 ?
Cheers,
Signature · 3 lines
Ludovic DROLEZ Free&ALter Soft 152, rue de Grigy - Technopole Metz 2000 57070 METZ tel : 03 87 75 55 21 fax : 03 87 75 19 26
Quoted 3 lines · Ludovic Drolez
Quoted 1 line
You can test 2.5. If it is wrong there I must submit a patch.
It seems to work perfectly with 2.5.56
Excellent.
Quoted 3 lines
But, I'm still reluctant to use an unstable kernel for backuping a partition. But maybe the 2.5 is stable enough to read blocks from IDE/SCSI drives, and send them over NFSv2 / IPv4 ?
Stable / unstable is not a binary decision. Some things are broken in 2.4. Many things are broken in 2.5. Still I use 2.5.recent on a daily basis without meeting bad problems (if I refrain from inserting and removing USB devices).
Try, and if it works for you, fine. But no guarantees given.
Andries