Re: [math-fun] Defective Sandisk uSD cards
I'm using the Linux "disk utility" benchmark function. I've done some more benchmarking on a variety of flash SD cards and USB flash drives. I'm seeing various kinds of performance. I tried a 16GB Sandisk "Ultra", which has excellent read rates (35 MB/s) and lousy write rates (3.4 MB/s avg). At 08:53 AM 2/15/2015, Tom Rokicki wrote:
Can you tell us how you tested? Secure Digital is very complicated internally and the speed rating is based on a very specific usage pattern.
While I'm sure you understand this, many forms of "testing" can actually have the effect of slowing down the cards dramatically.
On Sun, Feb 15, 2015 at 7:19 AM, Henry Baker <hbaker1@pipeline.com> wrote:
I purchased 4 32GB uSD cards from Costco yesterday, and found to my amazement that one of the devices was faulty: while the maximum write rate was >20 MB/s, its minimum write rate was 1.2 MB/s, with an average write rate of 5.1 MB/s.
While I suspect that this defective device will function correctly as a memory, I was amazed to find that perhaps 25% of these devices did not meet their speed requirement.
BTW, if you run Linux, there is a "benchmarking" function for the disk formatting program which is quite useful.
Now I'm going to have to test all of my SD cards in advance prior to using them. -- -- http://cube20.org/ -- [ <http://golly.sf.net/>Golly link suppressed; ask me why] --
* Henry Baker <hbaker1@pipeline.com> [Feb 16. 2015 08:57]:
I'm using the Linux "disk utility" benchmark function.
I've done some more benchmarking on a variety of flash SD cards and USB flash drives.
I'm seeing various kinds of performance.
I tried a 16GB Sandisk "Ultra", which has excellent read rates (35 MB/s)
Not bad, but "excellent" would be 100 MB/s.
and lousy write rates (3.4 MB/s avg).
Yes, lousy (here "excellent" would be 90 MB/s). (specs from MicroSDHC-Card 16GB - SanDisk Extreme Pro )
[...]
On Sun, Feb 15, 2015 at 7:19 AM, Henry Baker <hbaker1@pipeline.com> wrote:
I purchased 4 32GB uSD cards from Costco yesterday, and found to my amazement
Warning about buying this kind of things in a supermarket: they tend to offer low-grade electronics, sometimes with specs so bad you can't get anywhere else. If have been bitten by this. Find a good electronics shop, ask people who buy hardware on a regular basis to recommend such a shop (this may well be an internet-only business).
[...]
Now I'm going to have to test all of my SD cards in advance prior to using them.
Using _any_ storage (incl. RAM) without thorough prior testing is a bad (though common) mistake.
[...]
Best regards, jj
I buy memory from Crucial. -- Gene From: Joerg Arndt <arndt@jjj.de> To: math-fun <math-fun@mailman.xmission.com> Sent: Monday, February 16, 2015 1:31 AM Subject: Re: [math-fun] Defective Sandisk uSD cards * Henry Baker <hbaker1@pipeline.com> [Feb 16. 2015 08:57]:
I'm using the Linux "disk utility" benchmark function.
I've done some more benchmarking on a variety of flash SD cards and USB flash drives.
I'm seeing various kinds of performance.
I tried a 16GB Sandisk "Ultra", which has excellent read rates (35 MB/s)
Not bad, but "excellent" would be 100 MB/s.
and lousy write rates (3.4 MB/s avg).
Yes, lousy (here "excellent" would be 90 MB/s). (specs from MicroSDHC-Card 16GB - SanDisk Extreme Pro )
[...]
On Sun, Feb 15, 2015 at 7:19 AM, Henry Baker <hbaker1@pipeline.com> wrote:
I purchased 4 32GB uSD cards from Costco yesterday, and found to my amazement
Warning about buying this kind of things in a supermarket: they tend to offer low-grade electronics, sometimes with specs so bad you can't get anywhere else. If have been bitten by this. Find a good electronics shop, ask people who buy hardware on a regular basis to recommend such a shop (this may well be an internet-only business).
[...]
Now I'm going to have to test all of my SD cards in advance prior to using them.
Using _any_ storage (incl. RAM) without thorough prior testing is a bad (though common) mistake.
[...]
Best regards, jj _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
participants (3)
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Eugene Salamin -
Henry Baker -
Joerg Arndt