macsat.com OpenWrt and ASUS WL Forum

Hi all,

Using Macsat's example script for RRD I made my own modifications and the graphs are looking fine on my WL-500gP with WR RC6.
The script is generating the RRD-files and together with the PNG's are written to a USB memory-stick.
But know I wonder how long the memory-stick is going to survive the many 'writes' per day. Would it be better to write these files to memory (/tmp ?) and let cron make copies ones or twice a day to the stick?

greetingz from the Netherlands

Any given USB memorystick should be able to handle several 100.000 writes / reads.

A harddrive would be a better choice, but I dont think you will encounter problems with the USB Stick.

You can either do as you write - place the pics in /tmp - or you can get yourselves a harddrive instead of the USB Memory device :-)

...or you can just use the memory stick, and hope it works. My guess is that you wont see problems for as longs as you are using it. Hardware tend to outdate before it breaks these days :-)

Reference: http://en.wikipedia.org/wiki/USB_flash_drive#Weaknesses

Macsat, thanks for your answer. I appreciate your website, tutorials and scripts: thanks again! It really helped me, the beginner/novice I am.

About the memory, I'm a bit confused now. When I save files to /tmp they don't survive a power-cycle but when saved in for instance /www they do survive. Is it just /tmp which is RAM or can you explain what dirs are NVRAM and what dirs are RAM?

Ed

/tmp is RAM

All other mountpoints (except the ones you made for usb flash drive) is in the Flash chip in the device (like nvram - which is in a dedicated area of the flash chip).

Ok, that sounds logical. I could not find this info anywhere.
So this means that writing the PNG's to /www/images writes to NVRAM? This makes me concerned about the lifespan of the router  :-\
Is it possible to let the BusyBox httpd read the images from /tmp/images ?

I guess an easy way was to place the images in /tmp/images and then make a symlink in /www like this:


But when you reboot the router, the images will be lost !

I doesn't know too much about this topic nor about filesystems but after I read this: http://en.wikipedia.org/wiki/JFFS2
I guess that the memory stick would resist a bit longer.

I've been thinking along the same lines, but was told off by someone working at Kingston:
These flash memory devices have their own load-leveling software on board to even out load to all parts of the memory. Using JFFS2 would be counter-productive, since the load-leveling algorithms in the filesystem and on the stick will work against each other.
Use any non-journaling file system on the flash unit - ext2 would be a good choice.
Or adopt my layout: I am using two flash sticks in my routers: one for more or less static data and one for often changing data. Then I use a cron job to backup data from the often changing flash onto the other one every 4 hours. I also have that done before a controlled reboot of the router. Thus I loose only 4 hours of data in worst case, and I dont have to have an expensive, noisy and eventually unreliable hard disk. Flash memorys are cheap nowadays - I pay 180SEK for 1Gb ~20EUR, so I can afford to change the often changing flash when it fails - but it has not failed yet.

Sounds like a good way. And yes - flash is very very cheap.

I have a 500GB Harddrive attached, as I am using it as a NAS, so I dotn bother about flash memory devices :)