Can a loop thrash a disk?

lucmove · 05-05-2023, 01:10 PM

Code:

#!/bin/sh

for i in `seq 1 10`
    do echo $i >> loop.txt
done

Does that code write to the loop.txt file 10 times? How about `seq 1 10000000`? Does that write to disk 10 million times?

I am specifically concerned with wearing out my SSD.

pan64 · 05-05-2023, 02:02 PM

you need to read about disk cache. for example: https://foxutech.com/linux-memory-and-disk-caching/

michaelk · 05-05-2023, 02:28 PM

Look at the specifications of the SSD and post what the value of its TBW or DWPD. DWPD is the amount of drive capacity you can write per day over the warranty period. TBW is the total number of writes for the life of the drive and from there you can determine the writes per day. In most cases that far exceeds what most home users normally write to disk.

MadeInGermany · 05-05-2023, 04:28 PM

In most cases there is enough free RAM, so buffering and few bundled disk writes take place.
But if you want to be safe then optimize your code

Code:

for i in `seq 1 10`
    do echo $i
done > loop.txt

dugan · 05-05-2023, 05:08 PM

Put loop.txt on tmpfs when it's being written to, and move it to the SSD after that's all done?

Guttorm · 06-19-2023, 08:53 AM

Hi

Doing a lot of file open, write, close, is slightly slower, but not that much.

The kernel has a buffer and will not write to disk as long as there is free memory, or a "commit interval" setting is reached. I think it's 5 seconds by default on ext4.

I have a Rasperry PI (used as server), and added "noatime,commit=10800" in fstab. Then it will take up to 3 hours to get written disk. Of course I lose more on power failure, but it's ok for me.

It's useful for sd-cards and when it's written to /var/log or other places.

You can use the command "sync" when you want it to actually write to disk.

BW-userx · 06-19-2023, 09:13 AM

mod your fstab to put /tmp into ram
tmpfs /tmp tmpfs defaults,noatime,size=3G 0 0

size part is not actually necessary size=3G not needed unless you want to limit it to whatever size you want manually ( i just copy pasted that off my fstab)
then write to /tmp to cut down/off writes to the ssd

Code:

 #!/bin/sh

for i in `seq 1 10`
    do   echo $i >> /tmp/loop.txt

done
cp /tmp/loop.txt ~/

something like that, and stuff in /tmp is lost every time the PC looses electricity

Jan K. · 06-19-2023, 10:15 AM

I doubt you are able to wear out the SSD no matter the number...

https://www.howtogeek.com/806926/wha...mean-for-ssds/

bigearsbilly · 06-21-2023, 05:27 AM

I should think it's Ok as it's appending >> not overwriting.

BW-userx · 06-21-2023, 06:45 AM

Quote:

Originally Posted by Jan K.

I doubt you are able to wear out the SSD no matter the number...

https://www.howtogeek.com/806926/wha...mean-for-ssds/

putting it into RAM still cuts down on read writes to a disk (SDD) nonetheless thus prolonging its life cycle

Jan K. · 06-21-2023, 11:36 AM

The write process in op means you'll run out of disc space years before disc is worn out...

It's easy to calculate disc's life by looking at the number of bytes writes per day divided in TBW... we're talking decades. The disc will be replaced by other reasons than worn out.

I have an SSD you may try to wear out!