Re: [linux] September 2021 Meeting - 2021-09-02 @ 19:00
On Thu, 2 Sep 2021, Jean-Francois Messier wrote: I connected on the link, and it says that the next meeting is on 2021-06-03. This will be tomorrow, Friday. What about tonight ? Or am I too early ? Just too early. Standby! Brett To unsubscribe send a blank message to linux+unsubscr...@linux-ottawa.org To get help send a blank message to linux+h...@linux-ottawa.org To visit the archives: https://lists.linux-ottawa.org
Re: [linux] September 2021 Meeting - 2021-09-02 @ 19:00
I connected on the link, and it says that the next meeting is on 2021-06-03. This will be tomorrow, Friday. What about tonight ? Or am I too early ? On 2021-08-29 9:41 p.m., Scott Murphy wrote: When: Thursday, September 2, 2021 Time: 19:00 Where: jitsi video conference For those new to Linux, John has a talk titled: “Editors”. Once John has finished, Scott will give a talk on Balena “Cloud Services” Results. This month’s code: LinuxOttawa20210902 Meeting Details: The meeting URL will now be a fixed URL, https://six.linux-ottawa.org and should be up for connection by 18:30 on meeting nights and will vanish shortly after the meeting has concluded. You will be joining as anonymous guests, so you will not have a username or password. If it asks for a username and password, it has not been started yet. I will be attempting to have it running by 18:45. It may be online earlier, but it should be online by then. Rules/Procedures/Common-Sense: Video and audio will be disabled when you join. In order to make sure the experience is a reasonable one for all involved, the presenter will share their screen-window-whatever they are comfortable with and you will see it quite clearly. Rather than unmute, pressing your space bar will unmute your microphone while pressed, so you can try that to ask questions. There is also the chat window, which no longer appears to obscure the rest of the session (maybe on small monitors?) Feel free to post questions and as opportunity presents itself and the presenter notices, they will get answered. After the presentation is completed, feel free to unmute and have a normal voice/video Q To unsubscribe send a blank message to linux+unsubscr...@linux-ottawa.org To get help send a blank message to linux+h...@linux-ottawa.org To visit the archives: https://lists.linux-ottawa.org
Re: [linux] Veritasium video on the frequency of bit flips
> On Sep 3, 2021, at 05:09, Brett Delmage > wrote: > > Does anyone on this list run ZFS without ECC? > I run ZFS in my home NAS. > I always understood it was a risky filesystem choice without ECC. I really do > not want to have extensive filesystem corruption because of a bit flip, so > have not used it. > A bit flip in the wrong place can destroy any file system and any computer. ZFS is not really any different in this regard. I run ZFS because it’s the only mature F/S which does checksumming across it’s data, not just the metadata. It’s slower but that’s OK. Now I only use JBOD mode on any of my systems. If I need data redundancy, I sync the data between different disks using rsync/unison, preferably across different boxes and locations. I use to use RAID-1 (or ZFS equiv) for redundancy but I have had enough HDD failures (consumer versions) that I no longer trust RAID because of possible rebuild problems. I no longer use RAID for any data I care about due to latency and higher probability of rebuild failure. RAID’s throughput advantage no longer matter much to me because of SSD. Spinning rust latency is much more of an throughput issue. With big disks, rebuilding RAID-5 arrays has greater risks catastrophic failure (and can take forever in corporate settings). The time for RAID has gone by.. If you need more throughput then m.2 NVME SSD can provide (editing raw 8K videos is one of the few I can think of), buy a PCIe flash card. Those things run close to full PCIe bus speed with multiple lanes. My $0.02 worth. Spencer To unsubscribe send a blank message to linux+unsubscr...@linux-ottawa.org To get help send a blank message to linux+h...@linux-ottawa.org To visit the archives: https://lists.linux-ottawa.org
RE: [linux] Veritasium video on the frequency of bit flips
-Original Message- From: Dianne Skoll >I wonder about flash memory. As flash memory cells shrink, could a cosmic ray flip the charge on the floating gate? And if so, does flash have the equivalent of ECC? Oh, it gets worse than that. The charge in a cell can leak if it is not refreshed. And with various flash memories accessing the bit or surrounding bits can change the charge in the cell or on the gate which can effect the state of the bit. An SLC memory cell contains basically 2 voltage levels representing 0/1 for a single bit. MLC memory cells have 4 voltage levels representing 2 bits. TLC cells have 8 voltage levels representing 3 bits. You get more bits per cell but they become far more sensitive to charge changes. If you don't have some form of ECC, your data will become corrupted. Data is kept in blocks and the controllers for flash memories should keep track of the number of correctable errors in a block. If the error count gets too high, it should copy/correct the data into a spare block and map the spare block into the affected location. The old block can be erased (electrically different than just writing the data). The erasure can be enough to revive the block and it is put on the spare list. Some of the charge build up cannot be fixed by erasure. If this is the case, then the block is completely retired. Gary To unsubscribe send a blank message to linux+unsubscr...@linux-ottawa.org To get help send a blank message to linux+h...@linux-ottawa.org To visit the archives: https://lists.linux-ottawa.org
Re: [linux] Veritasium video on the frequency of bit flips
Even here on Earth you should use ZFS or equivalent for data you care about -- "You should sit in nature for 20 minutes a day Unless you are busy - then you should sit for an hour" - Zen Proverb
Re: [linux] Veritasium video on the frequency of bit flips
On Thu, 2 Sep 2021, Ian! D. Allen wrote: At 17m53s: "On one five-day [Space Shuttle Mission] there were 161 separate bit flips." Okay, maybe we *do* need ECC RAM. Does anyone on this list run ZFS without ECC? I always understood it was a risky filesystem choice without ECC. I really do not want to have extensive filesystem corruption because of a bit flip, so have not used it. To unsubscribe send a blank message to linux+unsubscr...@linux-ottawa.org To get help send a blank message to linux+h...@linux-ottawa.org To visit the archives: https://lists.linux-ottawa.org
Re: [linux] Veritasium video on the frequency of bit flips
On Thu, Sep 2, 2021, at 4:00 PM, Dianne Skoll wrote: > On Thu, 2 Sep 2021 15:39:37 -0400 > "Ian! D. Allen" wrote: > > > At 17m53s: "On one five-day [Space Shuttle Mission] there were 161 > > separate bit flips." > > > Okay, maybe we *do* need ECC RAM. > > Certainly on the space shuttle. Probably on important servers on Earth. > > I wonder about flash memory. As flash memory cells shrink, could a cosmic > ray flip the charge on the floating gate? And if so, does flash have the > equivalent of ECC? yeah flash has the same problem. last time I worked with it (8 years ago) it was either BCH based ECC in software or hardware. (Some flash controllers have a controller with BCH in hardware) I tried running a machine with a buggy BCH implementation and it would fail to boot in under a day and took about 1 month to debug -- which is how I know this. To unsubscribe send a blank message to linux+unsubscr...@linux-ottawa.org To get help send a blank message to linux+h...@linux-ottawa.org To visit the archives: https://lists.linux-ottawa.org
[linux] Veritasium video on the frequency of bit flips
Veritasium video on the frequency of bit flips: https://www.youtube.com/watch?v=AaZ_RSt0KP8 "The Universe is Hostile to Computers" At 17m53s: "On one five-day [Space Shuttle Mission] there were 161 separate bit flips." Okay, maybe we *do* need ECC RAM. -- | Ian! D. Allen, BA, MMath - idal...@idallen.ca - Ottawa, Ontario, Canada | Home: www.idallen.com Contact Improvisation Dance: www.contactimprov.ca | Former college professor (Free/Libre GNU+Linux) at: teaching.idallen.com | Improve democracy: www.fairvote.ca and Defend digital freedom: www.eff.org To unsubscribe send a blank message to linux+unsubscr...@linux-ottawa.org To get help send a blank message to linux+h...@linux-ottawa.org To visit the archives: https://lists.linux-ottawa.org
