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raid [2021/12/05 22:49] – vissieraid [2021/12/08 04:36] (current) – [Trying to get more performance] vissie
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 Your RAID 5 array should now automatically be assembled and mounted each boot. Your RAID 5 array should now automatically be assembled and mounted each boot.
 +
 +=====Trying to get more performance=====
 +  echo 16384 > /sys/block/md0/md/stripe_cache_size
 +  sudo blockdev --setra 65536 /dev/md0
 +
 +Increase speed limits
 +The easiest thing to do is to increase the system speed limits on raid. You can see the current limits on your system by using these commands:
 +  sudo sysctl dev.raid.speed_limit_min
 +  sudo sysctl dev.raid.speed_limit_max
 +These values are set in Kibibytes per second (KiB/s).
 +
 +You can put them to high values:
 +  sudo sysctl -w dev.raid.speed_limit_min=100000
 +  sudo sysctl -w dev.raid.speed_limit_max=500000
 +
 +Increase stripe cache size
 +By allowing the array to use more memory for its stripe cache, you may improve the performances. In some cases, it can improve performances by up to 6 times. By default, the size of the stripe cache is 256, in pages. By default, Linux uses 4096B pages. If you use 256 pages for the stripe cache and you have 10 disks, the cache would use 10*256*4096=10MiB of RAM. In my case, I have increased it to 4096:
 +  echo 4096 | sudo tee -a /sys/block/md0/md/stripe_cache_size
 +The maximum value is 32768. If you have many disks, this may well take all your available memory. I don't think values higher than 4096 will improve performance, but feel free to try it ;)
 +
 +Increase read-ahead
 +If configured too low, the read-ahead of your array may make things slower.
 +
 +You can see get the current read-ahead value with this command:
 +
 +  sudo blockdev --getra /dev/md0
 +These values are in 512B sector. You can set it to 32MB to be sure:
 +
 +  sudo blockdev --setra 65536 /dev/md0
 +This can improve the performances, but don't expect this to be a game-changer unless it was configured really low at the first place.
 +
  
  
raid.1638773377.txt.gz · Last modified: 2021/12/05 22:49 by vissie

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