ALWAYS close USB flash drive before removing?

Do I always need to close or stop a USB flash drive before I remove
it?

I'm using XP. In XP's Device Manager there is an entry for Disk
Drives and when I look at the Policies tab for the flash drive, it
says:

"Optimized For Quick Removal. This setting enables
write caching on the disk and in Windows, so you can
disconnect this device without using the Safe Removal
icon."

My friends get upset if I don't use the Safe Removal process when
their USB memory is in my PC. Maybe they're repeating a mistake? Or
is there a reason which I'm missing that says I should always use
Safe Removal?

Eddie wrote:
Do I always need to close or stop a USB flash drive before I remove
it?

I'm using XP. In XP's Device Manager there is an entry for Disk
Drives and when I look at the Policies tab for the flash drive, it
says:

"Optimized For Quick Removal. This setting enables
write caching on the disk and in Windows, so you can
disconnect this device without using the Safe Removal
icon."

My friends get upset if I don't use the Safe Removal process when
their USB memory is in my PC. Maybe they're repeating a mistake? Or
is there a reason which I'm missing that says I should always use
Safe Removal?

The main problem with removing USB drives without "safe removal" (or
umount on Linux) is that the OS could still have data in its write
buffers. If you remove the flash drive before the write is complete,
you will lose data, corrupting the file that is being written, and
possibly corrupting the FAT (and therefore lots more of the flash disk).

The "optimize for quick removal" makes windows save as little in the
write buffers as possible, minimising your risks, but you are still
risking data loss and file corruption. The other choice is to store
lots more in the write buffers - that makes the flash disk far faster
for writing, especially for writing lots of small files, but means
greater risk of corruption if you don't remove it safely.

So you should /always/ use safe removal, unless you haven't written
anything to the disk.

"Eddie" wrote in message
...
Do I always need to close or stop a USB flash drive before I remove
it?

I'm using XP. In XP's Device Manager there is an entry for Disk
Drives and when I look at the Policies tab for the flash drive, it
says:

"Optimized For Quick Removal. This setting enables
write caching on the disk and in Windows, so you can
disconnect this device without using the Safe Removal
icon."

My friends get upset if I don't use the Safe Removal process when
their USB memory is in my PC. Maybe they're repeating a mistake? Or
is there a reason which I'm missing that says I should always use
Safe Removal?

Windows doesn't always write immediately to a USB stick, but quickly caches
things and writes to the USB drive at its own speed (like a print queue) so
if you drag files across, then immediately remove the stick you might find
things missing or corrupted. If the stick has an LED, then you can tell when
its ready/finished.

In comp.sys.ibm.pc.hardware.storage GT wrote:
"Eddie" wrote in message
...
Do I always need to close or stop a USB flash drive before I remove
it?

I'm using XP. In XP's Device Manager there is an entry for Disk
Drives and when I look at the Policies tab for the flash drive, it
says:

"Optimized For Quick Removal. This setting enables
write caching on the disk and in Windows, so you can
disconnect this device without using the Safe Removal
icon."

My friends get upset if I don't use the Safe Removal process when
their USB memory is in my PC. Maybe they're repeating a mistake? Or
is there a reason which I'm missing that says I should always use
Safe Removal?

Windows doesn't always write immediately to a USB stick, but quickly caches
things and writes to the USB drive at its own speed (like a print queue) so
if you drag files across, then immediately remove the stick you might find
things missing or corrupted. If the stick has an LED, then you can tell when
its ready/finished.

That is dangerous. It may delee or interrupt writes for a short
time due to other things. The only safe opton is to use safe
removal and o wait until windows says that the stick can be removed.

That said, if you have mostlysmall writes, just janking the stick
out oftnen works, but can also result in mor or less subtle data
corruption, up to an including loss of all data on the stick.

Arno


--
Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email:
GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
----
Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans

In comp.sys.ibm.pc.hardware.storage Eddie wrote:
Do I always need to close or stop a USB flash drive before I remove
it?

I'm using XP. In XP's Device Manager there is an entry for Disk
Drives and when I look at the Policies tab for the flash drive, it
says:

"Optimized For Quick Removal. This setting enables
write caching on the disk and in Windows, so you can
disconnect this device without using the Safe Removal
icon."

That is basically a lie by omission. You still need to
wait until all writes are complete. The difference is that
windows will try hard to write immediately, but a) writes
can take time and larger ones can take a lot of time
and b) some other things can still prevent windows to
write immediately. Often this works, but you may still
loose all data on the stick or get corruption if you trust
this statement.

My friends get upset if I don't use the Safe Removal process when
their USB memory is in my PC. Maybe they're repeating a mistake? Or
is there a reason which I'm missing that says I should always use
Safe Removal?

Your friends are right. There are some advanced journalling
filesystems that can reliably minimize corruption if you remove
an USB stick during a write, but Wndows is not using them
and neither FAT nor NTFS is safe to remove during a write.

Obviously a file tat is bing written during remmoval will
always have some corruption as result, there is no way around
that.

Arno

--
Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email:
GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
----
Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans

On Nov 17, 5:26 am, Eddie wrote:
Do I always need to close or stop a USB flash drive before I remove
it?

Just remove it after done. Mine burnt out when I left it in -- end
LED light always flashed whether being written to not while it was
working.

On 11:32 17 Nov 2009, Arno wrote:

In comp.sys.ibm.pc.hardware.storage Eddie
wrote:
Do I always need to close or stop a USB flash drive before I
remove it?

I'm using XP. In XP's Device Manager there is an entry for
Disk Drives and when I look at the Policies tab for the flash
drive, it says:

"Optimized For Quick Removal. This setting enables
write caching on the disk and in Windows, so you can
disconnect this device without using the Safe Removal
icon."

That is basically a lie by omission. You still need to
wait until all writes are complete. The difference is that
windows will try hard to write immediately, but a) writes
can take time and larger ones can take a lot of time
and b) some other things can still prevent windows to
write immediately. Often this works, but you may still
loose all data on the stick or get corruption if you trust
this statement.

My friends get upset if I don't use the Safe Removal process
when their USB memory is in my PC. Maybe they're repeating a
mistake? Or is there a reason which I'm missing that says I
should always use Safe Removal?

Your friends are right. There are some advanced journalling
filesystems that can reliably minimize corruption if you remove
an USB stick during a write, but Wndows is not using them
and neither FAT nor NTFS is safe to remove during a write.

Obviously a file tat is bing written during remmoval will
always have some corruption as result, there is no way around
that.

Arno

Suppose I wait a few minutes after I moved a file to the flash
drive. Will the write cache be written out to the flash drive in
that period? Working like that is preferable because XP's Safe
Removal utility can be fiddly to launch.

I mean to ask, is it simply a matter of leaving ENOUGH TIME for the
write cache to be emptied by XP?

Or does the emptying of the write cache depend on OTHER FACTORS than
elapsed time?

Eddie wrote:

Do I always need to close or stop a USB flash drive before I remove
it?

I've been removing the drive immediately (all drives: USB, SD,
external HDD, ect) for years now and I've never had a problem. Course
I ways wait to remove it until a few moments after the lights stop
flashing. I'm sure you will hear from those who have had problems
though. It may depend on which app you are using to do the transfer.
Perhaps as in life it boils down to just how much of a hassle you are
willing put up with to be completely safe...

In comp.sys.ibm.pc.hardware.storage Eddie wrote:
On 11:32 17 Nov 2009, Arno wrote:

In comp.sys.ibm.pc.hardware.storage Eddie
wrote:
Do I always need to close or stop a USB flash drive before I
remove it?

I'm using XP. In XP's Device Manager there is an entry for
Disk Drives and when I look at the Policies tab for the flash
drive, it says:

"Optimized For Quick Removal. This setting enables
write caching on the disk and in Windows, so you can
disconnect this device without using the Safe Removal
icon."

That is basically a lie by omission. You still need to
wait until all writes are complete. The difference is that
windows will try hard to write immediately, but a) writes
can take time and larger ones can take a lot of time
and b) some other things can still prevent windows to
write immediately. Often this works, but you may still
loose all data on the stick or get corruption if you trust
this statement.

My friends get upset if I don't use the Safe Removal process
when their USB memory is in my PC. Maybe they're repeating a
mistake? Or is there a reason which I'm missing that says I
should always use Safe Removal?

Your friends are right. There are some advanced journalling
filesystems that can reliably minimize corruption if you remove
an USB stick during a write, but Wndows is not using them
and neither FAT nor NTFS is safe to remove during a write.

Obviously a file tat is bing written during remmoval will
always have some corruption as result, there is no way around
that.

Arno

Suppose I wait a few minutes after I moved a file to the flash
drive. Will the write cache be written out to the flash drive in
that period? Working like that is preferable because XP's Safe
Removal utility can be fiddly to launch.

I mean to ask, is it simply a matter of leaving ENOUGH TIME for the
write cache to be emptied by XP?

It is, but there is no reliable way to tell how much time is enough.

Or does the emptying of the write cache depend on OTHER FACTORS than
elapsed time?

The time the emptying takes can depend on other usage of the
filesystem, for example. Say you have a large weite request
that has aged in the background and reached the "must flush"
timeout, than that will be written before the USB stick is.

There are other conditions that can delay writing.

The problem is that there is no way to tell from the outside
and you will get corruption if you remove in the wrong Moment.
That said, it typically (low I/O load, no large writes, no
high CPU/hogh memory load tasks) works.

Arno
--
Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email:
GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
----
Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans

On Tue, 17 Nov 2009 10:26:38 GMT, Eddie
wrote:

Do I always need to close or stop a USB flash drive before I remove
it?

I'm using XP. In XP's Device Manager there is an entry for Disk
Drives and when I look at the Policies tab for the flash drive, it
says:

"Optimized For Quick Removal. This setting enables
write caching on the disk and in Windows, so you can
disconnect this device without using the Safe Removal
icon."

My friends get upset if I don't use the Safe Removal process when
their USB memory is in my PC. Maybe they're repeating a mistake? Or
is there a reason which I'm missing that says I should always use
Safe Removal?

All safe removal really does is wait to tell you it can be
removed if the buffer is not written out yet.

As for the optimized for quick removal setting, in use the
main difference is that this keeps the "copying..." visual
indicator window on screen until the copying is done, while
if you chose the other option the copying indicator window
will finish suggesting the copying is finished while all
that is necessarily done is all the data to be copied is now
in the windows buffer.

While writes can be delayed it is not by much, it would take
a fairly heavy use of the system to really delay by more
than the physical write speed and USB bus limitations cause.

IF your drive access LED works properly and you are familiar
with it, you can judge when writing is done by simply
observing several seconds of no activity, but certainly the
safest is to use the safely remove hardware feature.

The best thing to do is just respect your friend's wishes
and use it, regardless of whether it really matters... you
can't spend your life arguing with or educating people about
every little thing... and some of them will get offended.