Re: [BackupPC-users] Which FS?

> more disk activity than on a 'normal' directory. Sorting the stat()

> calls by inode number would help, but I doubt 'ls' is optimized for
> such an unusual usage case (but I haven't checked, so I might be wrong).

that is the job of the SCSI (and not SATA) command queuing,
reorder the requests to optimize the head seeks... that is
also why IDE suck so much

That is about 90% correct. in SATA the NCQ exists above the head controller. The head should tend to order the data due to the NCQ organizing the input stream better. SCSI and SAS actually have knowledge of the head position at the same level as the command queue which makes them more capable at such tasks. IDE is garbage, I agree.

But anyway, if someone is working under RAM pressure or
IO pressure, you have no cache, and without cache, all
HDs/OS/filesystems will take a HUGE performance hit

This is somewhat dependant on filesystem and IO Scheduler of the OS. Some filesystems excel under IO loads (ZFS) but shrivel and die under RAM pressure(ZFS). XFS is pretty much middle of the line while EXT3 runs very well with limited ram but chokes under IO pressure. In linux, the CFQ scheduler is very good under IO pressure but slows under low resource situations while the AS scheduler is not terribly fast overall but keeps its cool under the worst conditions.

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