PeteCresswell said:
"MicroSDXC Class 10 UHS-1 Memory Card".
Missing the details again. That's the generic specs for the device, not
a brand and model. No one yet knows WHICH device you actually have. I
picked one from a Google search and chose:
http://www.bhphotovideo.com/bnh/controller/home?O=&sku=886007&Q=&is=REG&A=details
Notice its specs say:
Read: 30 MB/s
Write: 10 MB/s
Either mention WHOSE device you are asking about or give a URL to it.
Claimed transfer rate = 30 MB/Sec.
Let's say it's really 20 MB/Sec.
12 GB = 12 x 2^30 bytes = 12,884,901,888 bytes
30 MB/s = 30 x 2^20 bytes/sec = 31,457,280 bytes/sec
12,884,901,888 bytes / (31,457,380 bytes/min) = 409.6 sec
409.6 sec x (1 min/60 sec) = 6.8 minutes
Plugging it into a USB adapter and copying a 12-gig movie to it,
So you were *writing* to the device. That means you get the 10 MB/s
transfer rate, NOT the 30 MB/s rate.
the
copy takes about 30 minutes.
30 minutes / 6.8 minutes = 4.4
You copy is taking more than 4 times longer than the specified transfer
rate for the device. EXCEPT that is for a read transfer and that is not
what you described. Instead you are writing to the device so you don't
get 30 MB/s but only 10 MB/s. Instead of being 4.4 times slower than
expect, the device is only 4.4 / (30 Mbps/10 Mbps) = 1.5 times slower.
The above calculations for 6.8 minutes to transfer 12 GB was at your
claimed 30 MB/s transfer rate. Since the transfer rate for a WRITE
which is what you are doing is a third of that speed (only 10 MB/s) then
the time to transfer would be 3 times longer, or 20.4 minutes.
30 minutes / 20.4 minutes = 1.5
The actual transfer rate is severely less than the published transfer
rate but it is still significantly different (50% more than published).
So what anti-virus program are you using? Did you disable it for the
huge file transfer? I've noticed that when WSUS offline (a means of
collecting updates for Windows & Office and storing them locally)
downloads a huge file that the process crawls because of the
interference by the AV program to interrogate EVERY single byte during
the transfer. If I temporarily disable the AV program, the file copy
goes very quickly.
This promises to be a recurrent task as
I load up my 10.1" tablet with a movie or three preparatory to taking a
trip.
Does the tablet have an anti-virus program, or other security software
that interrogates file creates and modifies?
Same copy SATA-disc-to-SATA-disc takes about 5 minutes.
Seems like a 20 MB/Sec transfer speed could support a copy time of about
10 minutes if the pipeline were fast enough.
My guess is that USB is the bottleneck and an eSATA reader might give me
that 10-minute transfer time - or something close to it.
USB 1.x:
Low bandwidth: 1.5 Mbps (187 KBps)
Full bandwidth: 12 Mbps (1.5 MBps)
USB 2.0:
Max signalling rate: 480 Mbps
(effective throughput of 280 Mbps or 35 MBps)
So it looks like the device supports USB 2.x. It also looks like you
couldn't distinguish between read and write speeds for the device -- but
then we don't know WHICH device you're asking about since you never
identified make and model. Plus there may be an AV program further
slowing the writes.
Before I blow seventy bucks on an eSATA-connected card reader as in
http://tinyurl.com/89twp43... Can anybody comment on my reasoning?
See what happens when you temporarily disable all your security
software, especially whatever anti-virus program you are using.