On Thursday 19 September 2019 03:59:24 Jonas Smedegaard wrote: > Quoting Gene Heskett (2019-09-18 21:19:45) > > > On Wednesday 18 September 2019 12:58:25 Jonas Smedegaard wrote: > > > Quoting Gene Heskett (2019-09-18 18:20:43) > > > > > > > On Wednesday 18 September 2019 11:36:41 John Hasler wrote: > > > > > Jonas writes: > > > > > > Please demonstrate just one single example of dd being > > > > > > faster than cp to transfer a full raw image to a raw device! > > > > > > > > > > On modern systems you would probably need to be doing terabyte > > > > > transfers between disks on the same machine. Back in the days > > > > > when a megabyte was a lot dd was *much* faster. > > > > > > > > > > On an SD card I think that the write speed of the card is > > > > > probably the limiting factor. > > > > > > > > It is, and the makers lie a lot, taking advantage of the > > > > buffering to get thier 100 MBs rating for small writes. For > > > > gigabyte transfers I often see sub 20 MB/S toward the end. But > > > > you may want to steer clear of the 64GB+ cards, exfat is > > > > creeping into the sdhc arena, and I either have a defective NEW > > > > PNY 64GB, or this stretch install can't touch it because its > > > > exfat. I bought 2 recently, same exact part number, slightly > > > > different card gfx, the 85 meg rated one doesn't mention exfat, > > > > works, the 100 MB/S rated one mentions exfat and is untouchable. > > > > > > Regarding quality of SD cards, I trust advices from Thomas Kaiser. > > > > > > Here's his advice on which brands to trust: > > > > Only a few vendors on this planet run NAND flash memory fabs, > > > > only a few companies produce flash memory controllers and have > > > > the necessary know-how in house. And only a few combine their > > > > own NAND flash with their own controllers to their own retail > > > > products. That's the simple reason why at least I only buy SD > > > > cards from these 4 brands: Samsung, SanDisk, Toshiba, Transcend > > > > > > Above quote is from > > > https://forum.armbian.com/topic/954-sd-card-performance/page/3/?ta > > >b=comments#comment-49811 which is linked from front page intro to > > > that thread - as part of this more general advice + warning not to > > > waste time reading the whole > > > > > > thread: > > > > Warning: This whole thread is only about historical information > > > > now since it's 2018 and we can buy inexpensive and great > > > > performing A1 rated SD cards in the meantime. Buying anything > > > > else is a mistake so directly jump to the end of the thread for > > > > performance numbers and recommendations. > > > > > > On a related note, here's Kaiser's more detailed notes on A1/A2 > > > rating: > > > https://github.com/ThomasKaiser/Knowledge/blob/master/articles/A1_ > > >and_A2_rated_SD_cards.md > > > > That also seems to be somewhat dated. And rather Sandisk promoting. > > No, quotes further up promotes brands closest to factories, and the > article closes above promotes A1/A2 labeling which is brand-agnostic > (yes, it proves its point by comparing cards from a single brand but > that's besides the point). > > > So I bought another to see if they were still as bad as a year ago. > > Which brand and model? Did it have either "A1" or "A2" printed on it?
SanDisk A1 10, ImageMate microSDXC UHS-1 64gb, UP TO 100 MB/s, haven't opened it yet. Much lower profile packaging than SamSung or PNY, will need a really sharp knife to liberate the actual card. > What are the comparable results from same tests? They are linked from > the article: > https://github.com/ThomasKaiser/sbc-bench/blob/master/sd-card-bench.sh That script looks to be pretty self destructive, but it might be interesting to kill the card just to see how long it lasts, but its $12 a card to find out. So I think I put the rpi4 raspbian buster on it when the heat sink and adapters arrive. Might even have raspbian buster 10.2 by then. ISTR you have to be able to run raspi-config & check the SSH box, as its (ssh) not run by default. So its not possible to navigate that unless someone knows what to do to it in the card reader to achieve the SSH function at bootup. Chicken vs egg problem from my point of view. But it might be a way to access it like I can when the older rpi3b stretch is plugged in. Curiosity is killing the cat. I *think* the gpio diffs are baked into the driver, so if I can install the stretch deb of linuxcnc I've built, then swap the new spi driver in, make the test cable, hook up a half blown mesa 7i90HD and see if it runs. Its the output side of the card thats blown. That will take some fooling around, which takes time. It might be that busters use of wayland is going to be a problem so we'll try this on stretch first. Linuxcnc's gfx aren't such that I can't export its screen to this machine with an ssh -Y login. But this won't until I rewrite that card with a RealtimePi kernel. Always somthing. Thanks Jonas Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene>
