Re: [Emc-users] I think its time to issue a warning about sandisk 32GB supposedly 2x speed of a samsung sd card

[Fox Mulder]

Am 20.12.2016 um 01:35 schrieb Bertho Stultiens:
> On 12/20/2016 01:10 AM, Gene Heskett wrote:
>> What has been other raspi users experience?  Is a sandisk crap?
> The *biggest* problem is a read/write file-system on an SD card. That
> kills about any cards within 1..3 months for me (especially when local
> logging is enabled). I normally have a R/O fs and remote logging.
> Everything else is in ramfs.

That's true. The same problem goes or ssd hard drives on the pc as well.
So some of the solutions for ssd's are also good for sd cards on the
rpi. Use of a ramdisk for directories like /tmp or /var/log is a good
idea because these are normally the most frequent written directories on
linux.

For the /tmp dir there is already a prepared systemd script which also
works on the rpi. Just execute the following commands which i found here
[1]:
sudo cp /usr/share/systemd/tmp.mount /etc/systemd/system/
sudo systemctl enable tmp.mount

For /var/log i didn't found a ready solution and wrote my own script. It
makes /var/log a ramdisk and copies the content at boot/shutdown from/to
a permanent directory /var/permanentlog so i don't loos all the logs. A
Cronjob also synchronizes the content every hour. If you are interested
you can try it out but the description is only in german on my wiki [2].
I use the script on my main PC and on my 24/7 RPI camera and it works
quite good. :)

Ciao,
 Rainer

[1]
https://wiki.debian.org/SSDOptimization#Reduction_of_SSD_write_frequency_via_RAMDISK

[2]
https://quakeman.mooo.com/wiki/doku.php?id=wissen:linux:ramdisk#var_log_in_eine_ramdisk_verlegen

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Re: [Emc-users] I think its time to issue a warning about sandisk 32GB supposedly 2x speed of a samsung sd card

[Bertho Stultiens]

On 12/20/2016 01:10 AM, Gene Heskett wrote:
> What has been other raspi users experience?  Is a sandisk crap?

For the small SD cards (<8G) it seems to work most of the time. I have
only seen few problems, but have not been able to pin it down on one
manufacturer.

The large ones (16+) can be a roll of the dice. However, very high speed
cards seem to be more problematic than the slower cards. However, this
is more anecdotal than scientifically tested. There is anecdotal
evidence that sandisk seems to have problems, but I have not been able
to confirm that with any hard evidence.

I usually use class 10 cards in 4G, 8G, or 16G and they are of several
brands. If my PC can handle it, then the PI can too. If a write error
occurs (on the PC) I will usually discard the card instead of trying again.

The *biggest* problem is a read/write file-system on an SD card. That
kills about any cards within 1..3 months for me (especially when local
logging is enabled). I normally have a R/O fs and remote logging.
Everything else is in ramfs.


-- 
Greetings Bertho

(disclaimers are disclaimed)

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[Emc-users] I think its time to issue a warning about sandisk 32GB supposedly 2x speed of a samsung sd card

[Gene Heskett]

Greetings all;

I bought one of them because the speed rating on the car said up to 
85megs/second. But,,, dd, writing the full jessie image, shows in the 
very immediate range of 15,8-16.2 megs for writing speed on either 
media.  And I had to write it twice before it would boot.

Then today as I was  following the script for the initial linuxcnc 
install, I've had buss errors that stopped it, each time requiring a 
powerdown reboot to restore "disk" access. 5 times so far today, and I 
have never gotten close enough to see if my cable is working with the 
rpspi driver.

So I'll do another powerdown, but while its down, the sandisk gets 
swapped out for the slower samsung, I've wasted enough time with this 
sandisk.  But the disk carrier gets traded out too as 2 more raspi's 
came in today.

What has been other raspi users experience?  Is a sandisk crap?

Cheers, Gene Heskett
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 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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