hard drive replication

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34 MB/sec is probably the maximum sequential read rate. You could come close to this number when reading very large unfragmented files at the beginning of the drive, but in real life the average speed would be more like 10 MB/sec.
 
34 MB/sec is probably the maximum sequential read rate. You could come close to this number when reading very large unfragmented files at the beginning of the drive, but in real life the average speed would be more like 10 MB/sec.
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I bought my wife an el cheapo flash drive (1 GB for $17) so she could
exchange occasional photos with our daughter. It took 15 minutes to
copy an 800 MB file from hard disk.

That's a rate of about 1 MB/sec.
 
(e-mail address removed) wrote
I am looking at this:

It is 500GB and says the Max Data Transfer Rate is 34 MB/s.
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Does this mean I could probably copy all the data off it in 15059
seconds?
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Nope, you wont get anything like that transfer rate in practice.
Or, is that sort of calculation usually invalid with HDs?
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Yes, particularly with externals.
 
Rod said:
(e-mail address removed) wrote



Nope, you wont get anything like that transfer rate in practice.


Yes, particularly with externals.
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Even by accessing each block sequentially, you won't get that?

Thanks.
 
Even by accessing each block sequentially, you won't get that?
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No, because the drive itself cant do that, even on the outer tracks
and the USB2 etc limits it below what the drive itself can do too.
 
I am looking at this:

http://google.xtechnology.com/scr/x...pt=Google&trID=o1ip4vMx16ibOHpQvRxYrMjUOybBNQ

It is 500GB and says the Max Data Transfer Rate is 34 MB/s.

Does this mean I could probably copy all the data off it in 15059
seconds?

Or, is that sort of calculation usually invalid with HDs?
Click to expand...

Yes it's invalid.

If you had unfragmented large files, you'd probably get
closer to 12MB/s average, perhaps as high as 24-30MB/s but
it's doubtful and depends on your system's actual USB
efficiency too.

With many thousands of smaller files, it will be
significantly slower.
 
Early flash memory ran at about 1 MB/sec and it seems that many manufacturers are still using that instead of newer memory that is much faster.

You can increase the write speed by enabling write caching, but be sure that you wait until the write is complete before unplugging the flash drive. It takes mine about 4 seconds to flush the write cache.
 
Early flash memory ran at about 1 MB/sec and it seems that many manufacturers are still using that instead of newer memory that is much faster.
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What is considered fast today?
You can increase the write speed by enabling write caching, but be sure that you wait until the write is complete before unplugging the flash drive. It takes mine about 4 seconds to flush the write cache.
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Assuming I use the same USB connector each time, does the binding of
the driver to the connecter preserve from one use to the next, in
which case, does the write cache stay enabled, or do you have to
enable it each time?
 
Citizen said:
What is considered fast today?
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The TechSolutions flash drive I bought a few months ago writes at 5 MB/sec and reads at 13 MB/sec (tested by copying a large file). If I recall correctly I read somewhere that some flash memory operates at twice this speed.
Assuming I use the same USB connector each time, does the binding of
the driver to the connecter preserve from one use to the next, in
which case, does the write cache stay enabled, or do you have to
enable it each time?
Click to expand...

The write cache will stay enabled for the drive. I don't know how it works but I assume that it depends on the volume label of the drive.
 
Early flash memory ran at about 1 MB/sec
Click to expand...


IIRC, there aren't any flash chips at the 1GB (per device,
pairs of chips in some) density that are that slow, but the
controller chip or USB1 mode could cause it.
 
What is considered fast today?
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8MB/sec write and over 15MB/s read, though it depends on
filesizes (fewer larger files are faster) and often
filesystem (FAT16 faster than FAT32, but FAT16 has the 2GB
limit). Speed is relative to cost too, and some devices
you'd USE the flash memory in won't be as fast as a computer
reader, so at some point paying more for higher performance
flash memory device is partially wasted.



Assuming I use the same USB connector each time, does the binding of
the driver to the connecter preserve from one use to the next, in
which case, does the write cache stay enabled, or do you have to
enable it each time?
Click to expand...

You do not have to enable each time, and it has nothing to
do with which USB connector.
 
The TechSolutions flash drive I bought a few months ago writes at 5 MB/sec and reads at 13 MB/sec (tested by copying a large file). If I recall correctly I read somewhere that some flash memory operates at twice this speed.
Click to expand...

If we take the fastest at 10 MB/s write speed, how does that compare
to HD write transfer? For example, I just copied a file that is 800 MB
in size from one HD to another (both on ch. 0) and it took 40 seconds.
That's 20 MB/sec.

I do not have any real experience with flash memory devices. People
are telling me they are very fast compared to hard disk transfers. I
am not finding that. In the case of the el cheapo flash disk, it did
the transfer at 1 MB/s, compared to 20 MB/s for 2 IDE HDs. Even if I
take your "twice the speed" figure, that's only 10 MB/s.

Something does not compute.
The write cache will stay enabled for the drive. I don't know how it works but I assume that it depends on the volume label of the drive.
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Or the so-called "signature". I run into problems every time I clone a
disk and want to mount it along with the original. The two disks are
identical in every way, so Win2K BSODs. I have to use Win98 version of
FDISK /MBR to zero out the first 4 bytes of the signature (a bug in
Win98 but I am exploiting it as a feature). Then I can have both disks
mounted at the same time.
 
IIRC, there aren't any flash chips at the 1GB (per device,
pairs of chips in some) density that are that slow, but the
controller chip or USB1 mode could cause it.
Click to expand...

My son has what he claims is a "fast" flash drive. I have not had a
chance to play with it myself so all I can do is take his word for it.
We used it on my machine and it went "fast". So at this stage I have
to conclude that my controller chip or ESB1 mode is not causing it.

He is coming over and I asked him to bring his "fast" flash stick for
testing.
 
Good point. If a flash drive operates at only 1 MB/sec it should be tried on a PC with a known good USB2 port.
 
I often read about the high speed of flash drives. This must me written by people that assume that an electronic device has to be faster than a mechanical device. The truth is that flash memory is extraordinarily slow compared to DIMMs, and hard drives are in fact faster. The only time flash memory is faster than a fast hard drive is when working with very small files, because memory does not have the relatively slow access time of a hard drive.
 
My son has what he claims is a "fast" flash drive. I have not had a
chance to play with it myself so all I can do is take his word for it.
We used it on my machine and it went "fast". So at this stage I have
to conclude that my controller chip or ESB1 mode is not causing it.

He is coming over and I asked him to bring his "fast" flash stick for
testing.
Click to expand...

Flash drives are still slower than an good newer hard drive.

Sometimes they can "seem" extremely fast because the OS is
caching subsequently read files, or writing into a buffer
that makes the copy or paste window disappear sooner, but
the buffer is still being written to the drive in the
background.

Even so, some flash drives are certainly faster than others,
but AFAIK, none can approach the 20MB/s write speed you
noted on your HDD. Write speed is still slower than read
speed on flash memory, it is possible to get reads of
20MB/s.
 
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