I've run a little wired benchmark on comparing Btrfs v0.19 and XFS:
There are 2000 directories and each directory contains 1000 files.
The workload randomly stat a file or chmod a file for 2000000 times.
And the number of stat and chmod are 50% and 50%.
I monitor the number of disk read requests
#Disk Write Requests, #Disk Read Requests, #Disk Write Sectors, #Disk Read Sectors
Btrfs 2403520 1571183 29249216 13512248
XFS 625493 396080 10302718 4932800
I found the number of write quests of Btrfs is significant larger than XFS.
I am not quite familiar with how btrfs commits the metadata change into the disks.
>From the website, it is said that btrfs uses COW B-tree which never overwrite previous disk pages.
I assume that Btrfs also keep an in-memory buffer to keep the metadata changes.
But it is unclear to me that how often Btrfs will commit these changes and what is the behind mechanism.
Could anyone please comment on the experiment results and give a brief explanation of Btrfs's metadata committing mechanism?
Sincerely,
Kai Ren--
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