I'm setting up a system for an off-site backup. It is a Raspberry Pi connected to two external hard disks. The data is written on both disks in parallel (this is not RAID 1, but two disks on which the backup service writes data individually).
The files will be mostly written, very rarely read. There are two patterns: most of the time, there would be a few small files written per minute. In some cases, there would be extensive writing of large files at a speed of 30 MB/s (if Raspberry Pi able to sustain such speed) for a duration of a few minutes to a few hours.
There would be around 1,000,000 files, using 2.5 TB in total. The largest files will be around 10 GB and there will be few of them; most will be from a few kilobytes to a few tens of megabytes. In order to avoid the issues Linux has with directories containing too much files, the data directory stores a maximum of thirty-two sub-directories, which in turn stores a maximum of thirty-two sub-sub-directories, and so on, six levels deep, limiting the number of files/directories of any directory to thirty-two.
The device would be powered through an UPS, but there is still a risk for it to be unintentionally unplugged/turned off while writing data. While a loss of a file which was being written when the device turned off/crashed is not a problem, it would be a serious issue if it affects other files.
The database (PostgreSQL) might be stored on those disks as well (although I haven't made my choice between storing it there or using the SD card of the Raspberry Pi and doing hourly backups on hard disks).
Would there be any benefit from using XFS?
Would there be any drawbacks?
From what I've read, XFS has benefits for situations where ext4 shows its limitations, like when one deals with exabytes of data, which is not exactly my case. It also seemed that XFS was slightly less stable a few years ago, but it doesn't seem to be the case any longer.
So, does it matter in my case, or my situation is too ordinary to justify a strong preference for a file system in particular?