[one-users] File system performance testing suite tailored to OpenNebula

[Carlo Daffara]

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" <gerry at scss.tcd.ie>
A: "Users OpenNebula" <users at 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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