Microzed 7010 Sluggish response

Hi bobdxcool,

I think you are probably on the right track with the SD card.  If you are running Ubuntu and have a page file being used then a slow memory leak can really bog down your system over time.

Take a look at this other thread where others suggest that using swap on an SD card is not a good idea:

http://askubuntu.com/questions/488033/is-having-swap-on-hard-drive-or-sd-card-better

As for the type of recommended SD card to use, I would suggest sticking with either the SanDisk, Delkin, or Kingston cards.  I don't say that just because we sell those cards here at Avnet, but because they are the primary cards that I use at my desk and I have yet to have problems with any of them on MicroZed.  I think you can also find SD cards out there (usually more expensive) which are rated for additional read write cycles than your everyday commercial SD cards, so that may also be an option.

Regards,

-Kevin

Currently a swap partition doesn't exist on my SD card. Also, since my system runs 24x7, is it recommended to use an SD card with more number of read/write cycles ? If so, which model SD card would you recommend ?

Hello,

As usual, I recommend Sandisk. I have no experience with the other brands, but the difference in price is probably small, and Sandisk has a long track record.

Running a filesystem on the SD is by far more demanding than its intended use (camera / cellular data storage): The OS constantly writes small pieces of data to the flash disk, so just by having the OS running, it's constantly being worn out.

A factor that is often overlooked is Write Amplification (WA):

https://en.wikipedia.org/wiki/Write_amplification

What Wikipedia doesn't emphasize enough is that the most important factor in keeping the WA down is that the SSD controller knows which write operation contains metadata that is likely to be overwritten soon, an which is constant data. This knowledge allows it to pack the written data in an efficient way.

It's a known secret that good SSD controllers detect the filesystem for this purpose. There's a reason they all arrive formatted with FAT32 (which is the most used), but the good ones work well with a variety of other filesystems. The difference between brands is not so much the flash memory itself, but the SSD controller's ability to keep the WA down by making good guesses on what kind of data is being written.

My hunch is that Sandisk flashes have an SSD that recognizes ext2/3/4 file system while others don't. That's probably why Sandisk works so well with Xillinux, and other flashes fail so soon.

A swap partition is completely unnecessary. And it would kill the flash device quite rapidly if it became necessary, as its content and read/write pattern is completely random.

Regards,
   Eli

Is something like sandisk ultimate or sandisk extreme recommended for use for my application as my application runs 24x7 (and so was thinking if it was better to have an industrial grade SD card) ? And also xillinux can support maximum 64gb Sandisk SD card ?

Hi,

I've actually had a good experience running a simple data logging program for about a year 24/7 on a Zybo card, with plain Xillinux. The program itself didn't write much, but anyhow -- there were no issues with the SD card.

So a plain and simple 8 GB card from Sandisk is probably the best choice. Larger cards may be less reliable, and I don't recommend industrial grade versions unless you're outside the commercial temperature range. Industrial products are less commonly used, and are often less reliable within the working conditions ranges that are supported by commercial versions.

Alternatively, you may try to run Xillinux (or another distribution, for that matter) with the root filesystem mounted read-only. On top of that, mount another partition (possibly FAT32 or ext4, but not encrypted or some loop mount) for the application data you need to save on the card.

This way you'll keep the amount of writes to what you actually need. But odds are that even that won't be necessary.

Regards,
   Eli

Hi there,

I want to let you know that we have a document which might be of some help:
http://zedboard.org/support/design/1521/11

Look for the Zynq How to Guides heading.  Find the document:
SD Card Advice for Zynq 7000 SoC Products, which lists some model numbers of cards that we or that we have been told by customers which appear to work.  I would agree with Eli, just about any SanDisk card will work for you.  Personally, I've use a few and never had any issues.

If you are going to be running 24x7, take his first post seriously.  Without write leveling you can destroy a SD card in no time!

--Dan

I also use the system for writing logs and for communication regularly with a server. The system scripts get updated like once a month through git.

Also, regarding mounting the root partition as read only and another partition for storing scripts and logs, can you please suggest me on how to do this (any lins would be helpful) ? I beleive xillinux already uses two partitions.

Also regarding temperatures, my systems are used in New York city where the temperatures go to negative range in the winter. My commercial grade microzed sits on a custom made carrier card PCB which is always usually in the 30-35 C temperature range. And this whole setup is inside a abs enclosure which is turn inside a waterproof stainless steel enclosure fixed on the streets. So since the carrier card PCB is always at a positive temperature, is it  recommend to continue with the commercial version of microzed ?

Hi,

The Commercial MicroZed is rated and tested from 0 to 70 degrees C. The Industrial MicroZed is rated and tested from -40 to +85 degrees C, with the exception that the microSD Card connector is only rated from -25 to +85 degrees C, as noted in the MicroZed HW Users Guide.

You should consider all the conditions your system may be operating in, including a situation where the system might be colder at initial power up, if that can occur in your application. So, if you might need to startup your system after it has been sitting at temps below 0 degrees C, I would suggest the Industrial version.

-Gary

Can you please help me on how to mount the root file system as read only and also create a application data partition ?