Hi Carlo,
Thanks for the reply. I should really look at XFS for the replication
and performance.
Do you have any thoughts on my second questions about qcow2 copies
form /datastores/1 to /datastores/0 in a single filesystem?
Regards,
Gerry
On 11/09/2013 12:53, Carlo Daffara wrote:
It's difficult to provide an indication of what a typical workload may be, as
it depends greatly on the
I/O properties of the VM that run inside (we found that the "internal" load of
OpenNebula itself to be basically negligible).
For example, if you have lots of sequential I/O heavy VMs you may get benefits
from one kind, while transactional and random I/O VMs may be more suitably
served by other file systems.
We tend to use fio for benchmarks (http://freecode.com/projects/fio) that is
included in most linux distributions; it provides for flexible selection of
read-vs-write patterns, can select different probability distributions and
includes a few common presets (like file server, mail server etc.)
Selecting the bottom file system for the store is thus extremely depending on
application, feature and load. For example, we use in some configurations BTRFS
with compression (slow rotative devices, especially when there are several of
them in parallel), in other we use ext4 (good, all-around balanced) and in
other XFS. For example XFS supports filesystem replication in a way similar to
that of zfs (not as sofisticated, though), excellent performance for multiple
parallel I/O operations.
ZFS in our tests tend to be extremely slow outside of a few "sweet spots"; a
fact confirmed by external benchmarks like this one:
http://www.phoronix.com/scan.php?page=article&item=zfs_linux_062&num=3 We tried
it (and we continue to do so, both for the FUSE and native kernel version) but for the
moment the performance hit is excessive despite the nice feature set. BTRFS continue to
improve nicely, and a set of patches to implement send/receive like ZFS are here:
https://btrfs.wiki.kernel.org/index.php/Design_notes_on_Send/Receive but it is still
marked as experimental.
I personally *love* ZFS, and the feature set is unparalleled. Unfortunately,
the poor license choice means that it never got the kind of hammering and
tuning that other linux kernel filesystem can get.
regards,
carlo daffara
cloudweavers
----- Messaggio originale -----
Da: "Gerry O'Brien" <ge...@scss.tcd.ie>
A: "Users OpenNebula" <users@lists.opennebula.org>
Inviato: Mercoledì, 11 settembre 2013 13:16:52
Oggetto: [one-users] File system performance testing suite tailored to
OpenNebula
Hi,
Are there any recommendations for a file system performance testing
suite tailored to OpenNebula typical workloads? I would like to compare
the performance of zfs v. ext4. One of the reasons for considering zfs
is that it allows replication to a remote site using snapshot streaming.
Normal nightly backups, using something like rsync, are not suitable for
virtual machine images where a single block change means the whole image
has to be copied. The amount of change is to great.
On a related issue, does it make sense to have datastores 0 and 1
in a single files system so that the instantiations of non-persistent
images does not require a copy from one file system to another? I have
in mind the case where the original image is a qcow2 image.
Regards,
Gerry
--
Gerry O'Brien
Systems Manager
School of Computer Science and Statistics
Trinity College Dublin
Dublin 2
IRELAND
00 353 1 896 1341
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