Disk question

[Peter Foldes]

A Linux "update" updates files that are already on the computer and
Very true and right on the money. Also I have used Knoppix,Ubuntu to boot Windows
when it does not boot. Excellent tools for dead Windows
--
Peter

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[J. D. Slocomb]

Not true. If you have a Grub update, it *will* write to the Windows
drive and if you have a kernel update, Ubuntu *won't* boot without the
Windows drive in the picture. I know because I have done it. And as I
plan to pull the Windows drive out and just use Ubuntu, it would be
foolish of me to do anything other than what I described above. Perhaps
there are some work arounds but I already have it set up exactly the way
I want it so why bother?

You are saying something wrong.

Assuming that you have one disk with Windows installed in one
partition, or several for that matter; and Linux installed in the
Linux partitions, regardless of how many there are; and you do a Linux
update, whether it installs a new kernel or not.

Linux will update files in the Linux partitions and will not change
files in the windows partitions. Linux will boot even though you were
to completely delete the windows software from the disk.

Now then. If you have windows installed on one disk then this disk
must be Disk A, or whatever name you care to assign to it, but the
disk that the BIOS will attempt to access first. The Master disk, lets
call it. And you have Linux installed on a totally separate and
different disk, which we can call the slave disk.

Now then, when you turn your computer on Bios spins up the Master disk
and attempts to read the Master Boot Record which consists of
something like the first 20, or so, sectors on the disk. It reads this
section into memory and assuming that there is computer instructions
there jumps to it to start the software boot action. If there is
nothing there or it can't be read you will see a error message that
"Can't find a bootable disk" or some such notice.

Now if you update your Linux the update still doesn't write to the
Windows disk but since the Master disk also contains the MBR the
machine will not boot unless the Master disk is connected.

However, you could still erase the windows partitions and as long as
you didn't tinker with the first few disk sectors you could boot
Linux.

You can prove this by copying the MBR to a file - you can use dd to do
that - and then erase the disk then copy the MBR back to the disk - so
that you know the MBR is in place and see whether the machine will
boot

Cheers,

John D. Slocomb
(jdslocombatgmail)

 

[Yousuf Khan]

Some time ago I installed a Seagate Barracuda 7200.12, 500 GB drive. I
installed Windows 7 and Fedora 12 and everything was fine until I
deleted the Linux partitions, re-partitioned, and installed Fedora 13.
Almost immediately after installing F-13 a warning appeared that the
disk was failing because there were too many bad blocks, apparently a
count of blocks that it was necessary to re-assign. However, the disk
continued to operate normally with no disk read or write errors.

After several months of warnings I elected to replace the disk with a
Western Digital 500 GB disk and have had no further warnings.

After replacing the disk I tested it using a Hitachi disk test
utility, which performs a 1.5 hour disk test. The results - "No
Errors" The same utility can check the S.M.A.R.T. disk functions and
that shows normal operation - no error.

Depends on which SMART fields you're looking at. When it comes to bad
sectors, there's three fields in particular that you need to look at
manually: (1) Reallocated Sectors Count, (2) Current Pending Sectors
Count, and (3) Offline Uncorrectable Sectors Count. That list is in
order of seriousness.

For #1 Reallocated Sectors, those are sectors that have been replaced by
the drive hardware itself from its spare pool. This is good news, it
means that the drives own failsafes have done their job, and bad sectors
have been successfully replaced by spare sectors, and your data is safe.
Having a few of these reallocated sectors is fine, but if you notice
them increasing over time, then it's time to do something.

For #2 Pending Sectors, this is a bit more serious. It means that some
sectors have been found to be iffy. They are still readable, but you can
not write to them anymore. They will get rewritten to spare sectors at
the next write of that sector. That is, unless there are no more spare
sectors left, then go see field #3.

For #3 Uncorrectable Sectors, this means that the pool of spare sectors
is now finished. Hopefully at this point the OS itself will start
blocking out bad sectors, thus reducing the overall capacity of the drive.

Now, many SMART reporters don't pay attention to #1 at all, they just
assume that the drive has done its job, and everything is fine. But they
don't monitor the drive over time, so they have no idea if it's remained
the same as before, or if it's increased since the last time it checked.
What might be happening here was that Fedora was one of the ones that
monitor disk health over periods of time, and it noticed counts
increasing. So don't just blindly follow the Hitachi or Seagate disk
monitoring tools' report that everything is fine, as in actual fact the
bad sectors might be increasing over time.

Now the question. Should I assume that the disk is usable based on the
Hitachi tests or should I scrap it based on the Fedora tests?

You can probably keep using it as a non-critical data drive. Just not a
boot drive.

Yousuf Khan

 

[Yousuf Khan]

Some time ago I installed a Seagate Barracuda 7200.12, 500 GB drive. I
installed Windows 7 and Fedora 12 and everything was fine until I
deleted the Linux partitions, re-partitioned, and installed Fedora 13.
Almost immediately after installing F-13 a warning appeared that the
disk was failing because there were too many bad blocks, apparently a
count of blocks that it was necessary to re-assign. However, the disk
continued to operate normally with no disk read or write errors.

After several months of warnings I elected to replace the disk with a
Western Digital 500 GB disk and have had no further warnings.

After replacing the disk I tested it using a Hitachi disk test
utility, which performs a 1.5 hour disk test. The results - "No
Errors" The same utility can check the S.M.A.R.T. disk functions and
that shows normal operation - no error.

Depends on which SMART fields you're looking at. When it comes to bad
sectors, there's three fields in particular that you need to look at
manually: (1) Reallocated Sectors Count, (2) Current Pending Sectors
Count, and (3) Offline Uncorrectable Sectors Count. That list is in
order of seriousness.

For #1 Reallocated Sectors, those are sectors that have been replaced by
the drive hardware itself from its spare pool. This is good news, it
means that the drives own failsafes have done their job, and bad sectors
have been successfully replaced by spare sectors, and your data is safe.
Having a few of these reallocated sectors is fine, but if you notice
them increasing over time, then it's time to do something.

For #2 Pending Sectors, this is a bit more serious. It means that some
sectors have been found to be iffy. They are still readable, but you can
not write to them anymore. They will get rewritten to spare sectors at
the next write of that sector. That is, unless there are no more spare
sectors left, then go see field #3.

For #3 Uncorrectable Sectors, this means that the pool of spare sectors
is now finished. Hopefully at this point the OS itself will start
blocking out bad sectors, thus reducing the overall capacity of the drive.

Now, many SMART reporters don't pay attention to #1 at all, they just
assume that the drive has done its job, and everything is fine. But they
don't monitor the drive over time, so they have no idea if it's remained
the same as before, or if it's increased since the last time it checked.
What might be happening here was that Fedora was one of the ones that
monitor disk health over periods of time, and it noticed counts
increasing. So don't just blindly follow the Hitachi or Seagate disk
monitoring tools' report that everything is fine, as in actual fact the
bad sectors might be increasing over time.

Now the question. Should I assume that the disk is usable based on the
Hitachi tests or should I scrap it based on the Fedora tests?

You can probably keep using it as a non-critical data drive. Just not a
boot drive.

Yousuf Khan

 

[J. D. Slocomb]

I could but what a waste of time when you consider Windows will be
leaving this box forever; I'm not getting any younger, and I'm more into
using a computer for business and pleasure than tinkering with different
OSes and booting strategies.

True. But it is nice to know how that damned thing did this

Cheers,

John D. Slocomb
(jdslocombatgmail)