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The time now is Wed 22 Nov 2017, 07:21
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 Forum index » Advanced Topics » Hardware
USB Flash Drive Quality
Moderators: Flash, Ian, JohnMurga
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linuxcbon

Joined: 09 Aug 2007
Posts: 1165

PostPosted: Tue 01 Aug 2017, 02:25    Post subject:  

BarryK wrote:
NO, it is not, dd will complete before flushing all data to the drive.

That's what I said, you didn't get it Cool . dd always completes before really writing, you cannot change that, except with "oflag=direct".
Now it depends on what you want to test, which flags you prefer, that will give different results.

BarryK wrote:
Also, writing to the filesystem on the drive is precisely what I want to test. Not raw writing to the drive.

OK then you didn't specify which file systems to test on or not, and this will also give different results.
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BarryK
Puppy Master


Joined: 09 May 2005
Posts: 8312
Location: Perth, Western Australia

PostPosted: Tue 01 Aug 2017, 04:47    Post subject:  

Edited, removed.
I have decided to bow out of this thread.

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linuxcbon

Joined: 09 Aug 2007
Posts: 1165

PostPosted: Tue 01 Aug 2017, 05:39    Post subject:  

What the ? OK, after so much dedication, I am not going to test anything for puppy for a long time ! You will have your peace and wont hear about me ! You will be happy ! BYE
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BarryK
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Joined: 09 May 2005
Posts: 8312
Location: Perth, Western Australia

PostPosted: Sun 06 Aug 2017, 21:29    Post subject:  

Have reconsidered, need to give an explanation why I backed out of this thread.

I was getting upset with the posts from linuxcbon. Then when tallboy erased his flash drive accidentally, using an example from linuxcbon, I had had enough.

The 'dd' utility is very powerful, and if you are not very careful, a drive or partition can get destroyed.

In my examples, dd has parameter "of=/mnt/sd*", for example "dd of=/mnt/sdc2", which is relatively safe as it is writing to a mount-point. And if for some reason the partition is not mounted there, then it is still a fairly ok situation.

If you have "of=/dev/sd*" then you have to be very very careful, and understand exactly what you are doing.

The other thing that annoyed me about the posts from linuxcbon, is he was using dd without all the extra parameters, for example "bs=1M count=1024 conv=fdatasync oflag=direct".
These are the result of considerable thought and prior knowledge. Setting the block size to 1M (or higher) for example, is recommended for efficient writing to flash.

A little note about linuxcbon himself. He has annoyed a lot of people over the years, with what many consider to be nit-picking and trivial criticisms. However, I have found his feedback to be very helpful, sometimes he unearths things that have been overlooked.

So, I value his input, and have sent a pm to him explaining that.

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peterw

Joined: 19 Jul 2006
Posts: 273
Location: UK

PostPosted: Mon 07 Aug 2017, 09:38    Post subject: Sandisk USB  

Hi
Thought, since I have just got a couple on new USB sticks I would join the discussion and tell you about mine. I bought all they had in the store since they are Sandisk, Ultra Flair, USB Flash Drive, 64GB which I bought for £5.45 each. On the packet it says speed up to 150 MB/s and that will be a read speed under optimum conditions.

I used my Acer C720 Chromebook which has Slacko 6.3.2 loaded on it and the machine has a USB 3 port and a USB 2 port. I did the test with the original vfat file system on it. Results are:

USB 3 Port
dd if=/dev/zero of=/mnt/sdb1/dummyfile bs=1M count=1024 conv=fdatasync ofla>
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 19.8114 s, 54.2 MB/s

USB 2 Port

dd if=/dev/zero of=/mnt/sdb2/dummyfile bs=1M count=1024 conv=fdatasync oflag=direct
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 38.3976 s, 28.0 MB/s

dd if=/dev/zero of=/mnt/sdb1/dummyfile bs=1M count=1024 conv=fdatasync oflag=direct
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 37.385 s, 28.7 MB/s

It shows that even on a USB 2 port the USB 3 sticks perform well[/b]
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tallboy


Joined: 21 Sep 2010
Posts: 813
Location: Oslo, Norway

PostPosted: Fri 11 Aug 2017, 11:10    Post subject:  

BarryK, thank you for caring, but the mistake was on me. I broke Linux rule no.1, I was careless on the keyboard! Very Happy
peterw wrote:
It shows that even on a USB 2 port the USB 3 sticks perform well

Good to know, I see others also have relatively better speed with USB3 pins in USB2 ports, and also with USB2 sticks in USB3 ports, compared to USB2 sticks in USB2 ports. One is often tempted by low price offers - usually for old USB2 sticks - and forget to take such things as speed into consideration.

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Billtoo


Joined: 07 Apr 2009
Posts: 3266
Location: Ontario Canada

PostPosted: Fri 11 Aug 2017, 11:37    Post subject: USB Flash Drive Quality  

I ran the test on a 16gb Lexar usb 3.0 flash drive that is plugged into a usb-2.0
port:

# sync
# echo 3 > /proc/sys/vm/drop_caches
# dd if=/dev/zero of=/mnt/sdh1/dummyfile bs=1M count=1024 conv=fdatasync oflag=direct
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 49.2252 s, 21.8 MB/s
#

It's one of those plastic jobs that has good speed but it's kind of
fragile.

******************************************************************************

Here's the same drive plugged into a usb-3.0 port:

# sync
# echo 3 > /proc/sys/vm/drop_caches
# dd if=/dev/zero of=/mnt/sdh1/dummyfile bs=1M count=1024 conv=fdatasync oflag=direct
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 43.0959 s, 24.9 MB/s
#
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