Juan Piernas Canovas <piernas@xxxxxxxxxxx> writes:
[playing devil's advocate here]
If the data and meta-data devices of DualFS can be on different disks,
DualFS is able to READ and WRITE data and meta-data blocks in
PARALLEL.
XFS can do this too using its real time volumes (which don't contain
any metadata). It can also have a separate log.
But we are talking about a different case. What I have said is that if you use two devices, one for the 'regular' file system and another one for the log, DualFS is better in that case because it can use the log for reads. Other journaling file systems can not do that.
Also many storage subsystems have some internal parallelism
in writing (e.g. a RAID can write on different disks in parallel for
a single partition) so i'm not sure your distinction is that useful.
If you stripe two disks with a standard fs versus use one of themIf you have a RAID system, both the data and meta-data devices of DualFS can be stripped, and you get the same result. No problem for DualFS :)
as metadata volume and the other as data volume with dualfs i would
expect the striped variant usually be faster because it will give
parallelism not only to data versus metadata, but also to all data
versus other data.
Also I would expect your design to be slow for metadata read intensiveI do not think so. The performance of DualFS is superb in meta-data read intensive workloads. And it is also better than the performance of other file system when reading a directory tree with several copies of the Linux kernel source code (I showed those results on Tuesday at the LSF07 workshop).
workloads. E.g. have you tried to boot a root partition with dual fs?
That's a very important IO benchmark for desktop Linux systems.
-Andi