Hi everyone, I have set up a lvmcache lv (on archlinux) using as fast disk the emmc of my laptop and as slow one a microsd card inserted in the integrated slot, following the man instructions. Its dimensions are 10gb and 41gb respectively and I am using this lv as /home partition. I used default options, excluding having set 'writeback' as cachemode. After I transferred the data (30gb) I noticed that cache used blocks and cache dirty blocks were now both above 99.94%. When after some time I tried to turn off the laptop, the shutdown procedure, being unable to complete the lv unmounting in the time frame assigned to the task (4m), simply skipped it and the computer was forced to shut down. On next boots I found that when not booting in recovery mode the drive could not be mounted most of the times. In general, if I shutted down the system before the dirty blocks percentage went to 0%, it would become 100% all over again at the next boot. So I decided to change cachemode to 'writethrough' and wait for the cache dirty blocks to be zero to see if doing so would solve the problem. To my surprise, it took over 24 hours. With 0% dirty blocks, the system was obviously booting fine. Also, having previously switched to 'writethrough', I expected in general not to have dirty blocks at all anymore. Today I forgot to attach the power cable and the laptop shutted down because of low power. After this, booting has become difficult again and dirty blocks are again 99%. Also, judging from iostat output writes on the sd card (happening in the background I believe) are really really slow. I wanted to know: - if this behaviour is normal, - if there is a way to avoid it apart from clean shutting downs at 0% dirty blocks, - why do I have dirty blocks in 'writethrough' mode, - if there is a way to empty the cache without erasing the whole volume, - if there is a way to trigger the cleaning process directly with an 'high' priority. Cheers, Pellegrino
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