I’m slowly migrating a bunch of awesome things from a really old server, it’s still running Ubuntu 10.04.. to a really nice and shiny one. Which has 2 new 3TB HDDs in RAID 1, which are syncing..
<br /> cat /proc/mdstat<br /> md3 : active raid1 sda4[0] sdb4[1]<br /> 1847478528 blocks super 1.2 [2/2] [UU]<br /> [>....................] resync = 0.1% (2061952/1847478528) finish=28857.9min speed=1065K/sec<br />
That’s like 40 days of syncing.. surely we can do better than that? Can’t we speed up this MDADM RAID 1 rebuild?
Speeding Up MDADM RAID Rebuilds
Sure we can, we’re awesome, I’m awesome, you’re awesome, can I get a hell yeah? HELL YEAH!
Likes lots of things that are tuneable, we have to do NASTY things to /proc. This bit sets the minimum speed we want mdadm to go at.
<br /> cat /proc/sys/dev/raid/speed_limit_min<br /> 1000<br />
We’re greedy though and in the words of Tim Tool Time Taylor, MORE POWER. As root..
<br /> echo 50000 > /proc/sys/dev/raid/speed_limit_min<br />
We’ve just made mdadm run FIFTY TIMES faster. FOR FREE. We didn’t even swap out the SATA disks for SAS SSDs, we just changed a number ..
<br /> md3 : active raid1 sda4[0] sdb4[1]<br /> 1847478528 blocks super 1.2 [2/2] [UU]<br /> [=====>...............] resync = 26.0% (480866560/1847478528) finish=141.9min speed=160501K/sec<br />
Now 10 minutes later we’re already over 1/4 the way through, 2 hours left baby. Hell yeah.