4 ms·
Sequential scrub turns "let's read all the blocks in the order we see them in the metadata" into "let's separate this into a read and a dispatch phase, so we ca
by rincebrain 7y ago
Sequential scrub turns "let's read all the blocks in the order we see them in the metadata" into "let's separate this into a read and a dispatch phase, so we can group things we dispatch into sequential regions and make spinning disks less sad at the amount of random IO needed".
It's quite a dramatic improvement for pools on hard drives.
- pushpop 7y agoOh nice. Thank you for the explanation. Does that have an impact on how long a scrub takes? I’ve always loved the ability to do online scrubs but they can take a long time
- rincebrain 7y agoVery much so. Spinning disks are bad at seeking randomly, and turning lots of random IOs into a smaller number of relatively sequential IOs is a substantial win.