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[Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM
From: |
Javier Guerra |
Subject: |
[Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM |
Date: |
Fri, 23 Oct 2009 09:14:29 -0500 |
On Fri, Oct 23, 2009 at 5:41 AM, MORITA Kazutaka
<address@hidden> wrote:
> On Fri, Oct 23, 2009 at 12:30 AM, Avi Kivity <address@hidden> wrote:
>> If so, is it reasonable to compare this to a cluster file system setup (like
>> GFS) with images as files on this filesystem? The difference would be that
>> clustering is implemented in userspace in sheepdog, but in the kernel for a
>> clustering filesystem.
>
> I think that the major difference between sheepdog and cluster file
> systems such as Google File system, pNFS, etc is the interface between
> clients and a storage system.
note that GFS is "Global File System" (written by Sistina (the same
folks from LVM) and bought by RedHat). Google Filesystem is a
different thing, and ironically the client/storage interface is a
little more like sheepdog and unlike a regular cluster filesystem.
>> How is load balancing implemented? Can you move an image transparently
>> while a guest is running? Will an image be moved closer to its guest?
>
> Sheepdog uses consistent hashing to decide where objects store; I/O
> load is balanced across the nodes. When a new node is added or the
> existing node is removed, the hash table changes and the data
> automatically and transparently are moved over nodes.
>
> We plan to implement a mechanism to distribute the data not randomly
> but intelligently; we could use machine load, the locations of VMs, etc.
i don't have much hands-on experience on consistent hashing; but it
sounds reasonable to make each node's ring segment proportional to its
storage capacity. dynamic load balancing seems a tougher nut to
crack, especially while keeping all clients mapping consistent.
>> Do you support multiple guests accessing the same image?
>
> A VM image can be attached to any VMs but one VM at a time; multiple
> running VMs cannot access to the same VM image.
this is a must-have safety measure; but a 'manual override' is quite
useful for those that know how to manage a cluster-aware filesystem
inside a VM image, maybe like Xen's "w!" flag does. justs be sure to
avoid distributed caching for a shared image!
in all, great project, and with such a clean patch into KVM/Qemu, high
hopes of making into regular use.
i'd just want to add my '+1 votes' on both getting rid of JVM
dependency and using block devices (usually LVM) instead of ext3/btrfs
--
Javier
- [Qemu-devel] RE: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM, (continued)
- [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM, Nikolai K. Bochev, 2009/10/21
- [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM, Nikolai K. Bochev, 2009/10/21
- [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM, Avi Kivity, 2009/10/22
- [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM, Anthony Liguori, 2009/10/22
- [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM, MORITA Kazutaka, 2009/10/23
- [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM,
Javier Guerra <=
- Re: [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM, Chris Webb, 2009/10/23
- Re: [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM, Javier Guerra, 2009/10/23
- Re: [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM, Tomasz Chmielewski, 2009/10/23
- RE: [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM, Dietmar Maurer, 2009/10/25
- Re: [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM, Tomasz Chmielewski, 2009/10/26
- [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM, FUJITA Tomonori, 2009/10/23
- [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM, Avi Kivity, 2009/10/25
- [Qemu-devel] RE: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM, Dietmar Maurer, 2009/10/25
- [Qemu-devel] Re: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM, MORITA Kazutaka, 2009/10/26
[Qemu-devel] RE: [ANNOUNCE] Sheepdog: Distributed Storage System for KVM, Dietmar Maurer, 2009/10/23