So, the BSDs mostly use synchronous I/O and soft updates (i.e. metadata is written asynchronously). Linux uses asynchronous I/O by default, and has no support for soft updates. Common knowledge on Linux is that synchronous I/O will kill performance.
I do not think this is the case any more with modern hard drives. I am currently running with with my root and home partitions mounted synchronously, and everything works fine. Throughput is a little lower; but heavy I/O (like creating a VirtualBox drive) doesn't hang the system, which is usually what happens with the partitions mounted async.
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$ mount -l
/dev/root on / type ext4 (rw,sync,noatime,barrier=0,commit=0)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
/dev/sda3 on /home type ext4 (rw,sync,noatime,barrier=0,commit=0)
tmpfs on /dev/shm type tmpfs (rw)Using synchronous I/O on a desktop has an obvious benefit: files saved to the disk will be written right away, instead of waiting around in RAM for a while. If there's a power outage, you have a lower risk of losing data.
OTOH, there are two detriments aside from loss of throughput that come to mind:
- More writes to the disk means shorter battery life
- More writes also might mean more wear and tear
Not sure to what extent those issues would crop up on Linux; BSDs manage synchronous I/O without killing batteries and hard drives, but they use soft updates, and Linux doesn't. So mounting your partitions synchronously might be a bad idea on a laptop, or if you have a cheap hard drive.
Anyway... I'm not of the opinion that synchronous I/O is better (or worse) on hard drives than asynchronous, but I think it should be noted that it may be a useful option for desktop users, especially those who have frequent power outages or problems with data loss; and that it does not in fact ruin desktop performance, unless you use it with ext4 or xfs and barriers enabled.