10:13 a.m.
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/
It's not a POSIX FS but there is a FUSE client for it that can be
used to access and manipulate images. It's quite high speed but only
when used with O_DIRECT + aio. I tried to setup several KVMs on top of
a Pstorage mount using virt-manager. It worked good, but I had to:
1. tune cache and IO settings for every disk
2. disable space allocation by libvirt because it is using sync IO and
is therefore slow
I tried to find ways to solve the first issue and IMHO this can be
done by adding a way to specify per-pool defaults for cache and IO
settings. I didn't find any way for this in the current code and UI.
I'd like to add a new storage backend also that will be a 'dir' backend
with extra ability to manage Pstorage mount points and UI integration.
I'd like to merge my work to the main tree when it's finished if
possible.
What do you think about my plan? Can you please suggest me how to add
per-pool defaults the best way?
--
Alexander
10:09 a.m.
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.
It's not a POSIX FS but there is a FUSE client for it that can
be
used to access and manipulate images. It's quite high speed but only
when used with O_DIRECT + aio. I tried to setup several KVMs on top of
a Pstorage mount using virt-manager. It worked good, but I had to:
1. tune cache and IO settings for every disk
2. disable space allocation by libvirt because it is using sync IO and
is therefore slow
I tried to find ways to solve the first issue and IMHO this can be
done by adding a way to specify per-pool defaults for cache and IO
settings. I didn't find any way for this in the current code and UI.
I'd like to add a new storage backend also that will be a 'dir' backend
with extra ability to manage Pstorage mount points and UI integration.
I'd like to merge my work to the main tree when it's finished if
possible.
I don't think that putting cache/IO defaults in the XML is really
appropriate. There are too many different scenarios which want
different settings to be able to clearly identify one set of
perfect settings. I see this as primarily a documentation problem.
Someone needs to write something describing the diferrent settings
for each storage pool & what the pros/cons are for each. Downstream
app developers can then make decisions about suitable defaults for
their use cases
Daniel
--
|: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org -o- http://virt-manager.org :|
|: http://autobuild.org -o- http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
8:47 a.m.
В Thu, 7 Feb 2013 16:09:31 +0000
"Daniel P. Berrange" <berrange(a)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:
1. CEPH uses BTRFS which is not considered stable yet.
2. Sheepdog has only synchronous writes and poor performance.
3. Glusterfs doesn't offer strong consistency. Strong consistency is
required for real filesystems (NTFS, ext3/4, ...) because that's what
HDDs offer.
Please correct me if I'm wrong. I haven't tried these filesystems
myself, this is just a summary from our internal wiki.
Pstorage includes three components: metadata servers, chunk servers and
clients. Metadata servers hold distributed metadata and synchronize it
using PAXOS (this is how we offer strong consistency). Chunk servers
store replicated pieces of VM images. The preferred method of access is
FUSE client, but you are not limited to it. You can also access a
Pstorage cluster directly using client library (FUSE client uses it
too, of course). There is also an LD_PRELOAD library that intercepts
syscalls like open, read, write, etc. I think it's the same approach as
in Glusterfs.
FUSE client is very fast when used with O_DIRECT + aio. Synchronous
access is much slower. For example, on a single machine with one HDD
async access gives almost the speed of HDD: 120-130MB/s. Sync access is
about 2.5MB/s. AFAIK this cannot be fixed without some improvements in
the kernel. We have some patches but we don't expect them to reach
mainline soon. But we want to make it easy to use Pstorage with KVM/Xen
and libvirt now. BTW I think user-configurable per-pool defaults can be
useful for others as well.
> It's not a POSIX FS but there is a FUSE client for it that
can be
> used to access and manipulate images. It's quite high speed but only
> when used with O_DIRECT + aio. I tried to setup several KVMs on top of
> a Pstorage mount using virt-manager. It worked good, but I had to:
> 1. tune cache and IO settings for every disk
> 2. disable space allocation by libvirt because it is using sync IO and
> is therefore slow
>
> I tried to find ways to solve the first issue and IMHO this can be
> done by adding a way to specify per-pool defaults for cache and IO
> settings. I didn't find any way for this in the current code and UI.
> I'd like to add a new storage backend also that will be a 'dir' backend
> with extra ability to manage Pstorage mount points and UI integration.
> I'd like to merge my work to the main tree when it's finished if
> possible.
I don't think that putting cache/IO defaults in the XML is really
appropriate. There are too many different scenarios which want
different settings to be able to clearly identify one set of
perfect settings. I see this as primarily a documentation problem.
Someone needs to write something describing the diferrent settings
for each storage pool & what the pros/cons are for each. Downstream
app developers can then make decisions about suitable defaults for
their use cases
Do you mean that I should patch virt-manager/oVirt for per-pool defaults
instead? IMO it's a bad idea. Imagine that I create a pool on one
machine and select some reasonable defaults for this pool in this
instance of virt-manager. Then I create an image from another instance
of virt-manager on a different machine which doesn't have these
defaults and therefore will not set them. I think, this is not
user-friendly.
I already made a step-by-step guide about creating a VM on a pstorage
pool. It's not quite easy. You should definitely avoid preallocating an
image because it will be preallocated synchronously and also you have
to set cache=none and io=native before starting VM for the
installation or it will take hours.
I think selecting some reasonable defaults is the right thing instead
of forcing users to read documentation.
--
Alexander
9:27 a.m.
On 02/08/2013 06:47 AM, Alexander Gordeev wrote:
В Thu, 7 Feb 2013 16:09:31 +0000
"Daniel P. Berrange" <berrange(a)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
4:20 p.m.
В Thu, 7 Feb 2013 16:09:31 +0000
"Daniel P. Berrange" <berrange(a)redhat.com> пишет:
> It's not a POSIX FS but there is a FUSE client for it that
can be
> used to access and manipulate images. It's quite high speed but only
> when used with O_DIRECT + aio. I tried to setup several KVMs on top of
> a Pstorage mount using virt-manager. It worked good, but I had to:
> 1. tune cache and IO settings for every disk
> 2. disable space allocation by libvirt because it is using sync IO and
> is therefore slow
>
> I tried to find ways to solve the first issue and IMHO this can be
> done by adding a way to specify per-pool defaults for cache and IO
> settings. I didn't find any way for this in the current code and UI.
> I'd like to add a new storage backend also that will be a 'dir' backend
> with extra ability to manage Pstorage mount points and UI integration.
> I'd like to merge my work to the main tree when it's finished if
> possible.
I don't think that putting cache/IO defaults in the XML is really
appropriate. There are too many different scenarios which want
different settings to be able to clearly identify one set of
perfect settings. I see this as primarily a documentation problem.
Someone needs to write something describing the diferrent settings
for each storage pool & what the pros/cons are for each. Downstream
app developers can then make decisions about suitable defaults for
their use cases
If you are against changes in the XML maybe you are ok with a simpler
option: I create a storage backend for Pstorage, add two fields for
cache and io (or maybe just flags) to virStoragePoolTypeInfo and set
the right values for the new pool type. Then add some code to check
them to qemuBuildDriveStr (and to other drivers if possible, of course).
So no changes to XML and API. Is this better?
--
Alexander
3:57 a.m.
On Sun, Feb 10, 2013 at 02:20:02AM +0400, Alexander Gordeev wrote:
В Thu, 7 Feb 2013 16:09:31 +0000
"Daniel P. Berrange" <berrange(a)redhat.com> пишет:
> > It's not a POSIX FS but there is a FUSE client for it that can be
> > used to access and manipulate images. It's quite high speed but only
> > when used with O_DIRECT + aio. I tried to setup several KVMs on top of
> > a Pstorage mount using virt-manager. It worked good, but I had to:
> > 1. tune cache and IO settings for every disk
> > 2. disable space allocation by libvirt because it is using sync IO and
> > is therefore slow
> >
> > I tried to find ways to solve the first issue and IMHO this can be
> > done by adding a way to specify per-pool defaults for cache and IO
> > settings. I didn't find any way for this in the current code and UI.
> > I'd like to add a new storage backend also that will be a 'dir'
backend
> > with extra ability to manage Pstorage mount points and UI integration.
> > I'd like to merge my work to the main tree when it's finished if
> > possible.
>
> I don't think that putting cache/IO defaults in the XML is really
> appropriate. There are too many different scenarios which want
> different settings to be able to clearly identify one set of
> perfect settings. I see this as primarily a documentation problem.
> Someone needs to write something describing the diferrent settings
> for each storage pool & what the pros/cons are for each. Downstream
> app developers can then make decisions about suitable defaults for
> their use cases
If you are against changes in the XML maybe you are ok with a simpler
option: I create a storage backend for Pstorage, add two fields for
cache and io (or maybe just flags) to virStoragePoolTypeInfo and set
the right values for the new pool type. Then add some code to check
them to qemuBuildDriveStr (and to other drivers if possible, of course).
So no changes to XML and API. Is this better?
No, the hypervisor drivers can only access data that is available via
from the storage drivers via the XML or APIs. As I said before this is
a policy decision for application authors to take, not for libvirt
itself.
Daniel
--
|: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org -o- http://virt-manager.org :|
|: http://autobuild.org -o- http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
4:13 a.m.
В Mon, 11 Feb 2013 09:57:05 +0000
"Daniel P. Berrange" <berrange(a)redhat.com> пишет:
On Sun, Feb 10, 2013 at 02:20:02AM +0400, Alexander Gordeev wrote:
> В Thu, 7 Feb 2013 16:09:31 +0000
> "Daniel P. Berrange" <berrange(a)redhat.com> пишет:
>
> > > It's not a POSIX FS but there is a FUSE client for it that can be
> > > used to access and manipulate images. It's quite high speed but only
> > > when used with O_DIRECT + aio. I tried to setup several KVMs on top of
> > > a Pstorage mount using virt-manager. It worked good, but I had to:
> > > 1. tune cache and IO settings for every disk
> > > 2. disable space allocation by libvirt because it is using sync IO and
> > > is therefore slow
> > >
> > > I tried to find ways to solve the first issue and IMHO this can be
> > > done by adding a way to specify per-pool defaults for cache and IO
> > > settings. I didn't find any way for this in the current code and UI.
> > > I'd like to add a new storage backend also that will be a
'dir' backend
> > > with extra ability to manage Pstorage mount points and UI integration.
> > > I'd like to merge my work to the main tree when it's finished if
> > > possible.
> >
> > I don't think that putting cache/IO defaults in the XML is really
> > appropriate. There are too many different scenarios which want
> > different settings to be able to clearly identify one set of
> > perfect settings. I see this as primarily a documentation problem.
> > Someone needs to write something describing the diferrent settings
> > for each storage pool & what the pros/cons are for each. Downstream
> > app developers can then make decisions about suitable defaults for
> > their use cases
>
> If you are against changes in the XML maybe you are ok with a simpler
> option: I create a storage backend for Pstorage, add two fields for
> cache and io (or maybe just flags) to virStoragePoolTypeInfo and set
> the right values for the new pool type. Then add some code to check
> them to qemuBuildDriveStr (and to other drivers if possible, of course).
> So no changes to XML and API. Is this better?
No, the hypervisor drivers can only access data that is available via
from the storage drivers via the XML or APIs. As I said before this is
a policy decision for application authors to take, not for libvirt
itself.
Ok, I certainly see the point about policy decisions but shouldn't
libvirt store the selected policy somehow? :)
--
Alexander
7:39 a.m.
В Mon, 11 Feb 2013 09:57:05 +0000
"Daniel P. Berrange" <berrange(a)redhat.com> пишет:
On Sun, Feb 10, 2013 at 02:20:02AM +0400, Alexander Gordeev wrote:
> В Thu, 7 Feb 2013 16:09:31 +0000
> "Daniel P. Berrange" <berrange(a)redhat.com> пишет:
>
> > > It's not a POSIX FS but there is a FUSE client for it that can be
> > > used to access and manipulate images. It's quite high speed but only
> > > when used with O_DIRECT + aio. I tried to setup several KVMs on top of
> > > a Pstorage mount using virt-manager. It worked good, but I had to:
> > > 1. tune cache and IO settings for every disk
> > > 2. disable space allocation by libvirt because it is using sync IO and
> > > is therefore slow
> > >
> > > I tried to find ways to solve the first issue and IMHO this can be
> > > done by adding a way to specify per-pool defaults for cache and IO
> > > settings. I didn't find any way for this in the current code and UI.
> > > I'd like to add a new storage backend also that will be a
'dir' backend
> > > with extra ability to manage Pstorage mount points and UI integration.
> > > I'd like to merge my work to the main tree when it's finished if
> > > possible.
> >
> > I don't think that putting cache/IO defaults in the XML is really
> > appropriate. There are too many different scenarios which want
> > different settings to be able to clearly identify one set of
> > perfect settings. I see this as primarily a documentation problem.
> > Someone needs to write something describing the diferrent settings
> > for each storage pool & what the pros/cons are for each. Downstream
> > app developers can then make decisions about suitable defaults for
> > their use cases
>
> If you are against changes in the XML maybe you are ok with a simpler
> option: I create a storage backend for Pstorage, add two fields for
> cache and io (or maybe just flags) to virStoragePoolTypeInfo and set
> the right values for the new pool type. Then add some code to check
> them to qemuBuildDriveStr (and to other drivers if possible, of course).
> So no changes to XML and API. Is this better?
No, the hypervisor drivers can only access data that is available via
from the storage drivers via the XML or APIs. As I said before this is
a policy decision for application authors to take, not for libvirt
itself.
Ok, I'll do the storage backend then. If you accept it virt-manager (and
other clients) probably will be able to distinguish a local directory
from a Pstorage mount point.
--
Alexander
4332
days inactive
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7 comments
3 participants
participants (3)
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Alexander Gordeev -
Daniel P. Berrange -
Josh Durgin