G'day Tim, Thanks, that's interesting.
My best guess is you have a bad connector and the 24-hour thermal test you did fixed it. The problem may return. Another guess is that the card has the production state awareness feature [1], part of e.MMC v5.0, which uses the storage cells differently before they are enabled for normal use. The state can be changed with suitable tools, or will clear itself once enough data is written; followed by a power cycle. The result is a sudden increase in performance after that power cycle. Suggestions: - next time you want to erase a card, send it the erase command, which takes between three and fifteen seconds in my tests [2], - test the communications between the system and the card by measuring the sequential read performance; this is usually the easiest way to test communications, - try on a different XO-1.5, in case you have a faulty XO-1.5, and raise doubts if the performance differs, - try on a modern desktop system; that will isolate the problem to interoperability with the XO-1.5, - identify the kernel, in case you have a version that doesn't properly switch to 1.8V; if so, the slot on the XO-1.5 will run it at 3.3V, warm, and so the card firmware will intentionally slow the transfers to ensure compliance with thermal specifications, - try reseating the card in the adapter, and the adapter in the system, because a bad connection can show up as slow data rate, then re-test the communications, - if available, use uninit_bg when calling mke2fs, so that the "formatting" doesn't have to write much, - publish the dmesg fragment showing the card being detected. When thinking about problems with SD card, it is best to imagine it as a separate computer, in which you can't change the software. There's no telling what it will do. ;-) They are very complex systems, made to look simple. Plug and play, dumbing down. +CC devel@ for general XO-1.5 and SD card interest. References: 1. https://www.jedec.org/news/pressreleases/jedec-announces-publication-emmc-standard-update-v50 2. http://wiki.laptop.org/go/Firmware/Storage#How_to_quickly_erase_everything (but use http://wiki.laptop.org/go/Firmware/Storage#devalias_fsdisk first) On Tue, Jul 14, 2015 at 06:34:52PM -0400, Tim Moody wrote: > I have been around the block with a 128G micro sdcard allegedly from > Sandisk. I made various attempts at creating two partitions and > formatting them ext4, some of which progressed at the rate of > 10G/hour. > > I finally used dd to write /dev/zero to the entire device, which > took almost 24 hours. > > After that parted mklabel msdos and mkpart worked fine and mkfs.ext4 > also worked fine in a couple of minutes. > -- James Cameron http://quozl.linux.org.au/ _______________________________________________ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
