[libvirt] libvirt and Parallels Cloud Storage

[Josh Durgin]

On 02/08/2013 06:47 AM, Alexander Gordeev wrote:
> В Thu, 7 Feb 2013 16:09:31 +0000
> "Daniel P. Berrange" <berrange at redhat.com> пишет:
>
>> On Mon, Feb 04, 2013 at 08:13:20PM +0400, Alexander Gordeev wrote:
>>> Hi!
>>>
>>> I'd like to develop libvirt integration with Parallels Cloud
>>> Storage (Pstorage) which is a new distributed file system from
>>> Parallels designed specifically for storing VM images:
>>> http://www.parallels.com/products/pcs/cloud-storage/
>>
>> Yay, yet another filesystem :-( Everyone seems to think they need to
>> write their own custom network/cluster/cloud FUSE filesystem these
>> days.
>
> Do you think Parallels would invest many man-years of development if we
> could just take existing solutions? :) It offers some unique
> combination of features: strong consistency, replication,
> high-availability. Also it's very fast.
> Let's compare:

These are all incorrect afaik:

> 1. CEPH uses BTRFS which is not considered stable yet.

btrfs isn't required, xfs is actually recommended, and ext4 works fine
too. btrfs just happens to be more efficient for some workloads.

> 2. Sheepdog has only synchronous writes and poor performance.

sheepdog certainly has aio in their qemu driver, which is the main
interface. It also isn't a distributed filesystem, it's just block
storage.

> 3. Glusterfs doesn't offer strong consistency. Strong consistency is
> required for real filesystems (NTFS, ext3/4, ...) because that's what
> HDDs offer.

I'm pretty sure glusterfs is supposed to be strongly consistent,
although I haven't tested it myself.

Josh