October 4, 20241 yr I've been on a server upgrade (or side grade) journey for a week or so. Part of that was moving from 6 array data disks of various sizes (4/8/14TB) + 4 SSDs to 4 x 14TB data disks + 1 SSD.. This has meant juggling many TBs of data from smaller disks to larger disks, then shrinking the array, rebuild parity and now moving more data.. The one thing that bugged me is the HDDs will do 230->135MB/s for the parity rebuild, but moving data disk-disk I get ~60MB/s in normal write mode and ~70MB/s in Turbo Write (all using default settings). However, tonight, moving another 5TB (many ~10GB files) of data around I just start reading the Help on the tips and tweaks plugin page and see that the dirty_background_ratio and dirty_ratio values are default (10/20) and it mentions using smaller dirty_background_ratio values for some workloads (gaming?) and give it a go.. and Bam.. 100MB/s+ sustained disk to disk in Turbo Write mode and much less HDD 'thrashing' I've done 2TBs now without issue.. (Just tweaking a bit and 3%/10% for the two dirty ratios seems to be around 105MB/s sustained.) I see a few people struggling with the lower 60-70MB/s speeds in reconstruct write mode and just thought I'd throw it out there and see if what I am doing is not a good idea, or if it is just down to experimentation?
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