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Re: [libvirt] libvirt and Parallels Cloud Storage



On 02/08/2013 06:47 AM, Alexander Gordeev wrote:
В Thu, 7 Feb 2013 16:09:31 +0000
"Daniel P. Berrange" <berrange 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


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