thanks Yixin,
On Tue, Jul 4, 2023 at 1:20 PM Yixin Jin <yjin77(a)yahoo.ca> wrote:
Hi Casey,
Thanks a lot for the clarification. I feel that zonegroup made a great sense at the
beginning when multisite feature was conceived and (I suspect) zones were always syncing
from all other zones within a zonegroup. However, once the "sync_from" was
introduced and later the sync policy further enhanced the granularity of the control over
data sync, it seems not much advantage is left with zonegroup.
both sync_from and sync policy do offer finer-grained control over
which zones sync from which, but they can't represent a bucket's
'residency' the way that the zonegroup-based LocationConstraint does.
by redirecting requests to the bucket's resident zonegroup, the goal
is to present a single eventually-consistent set of objects per
bucket. while features like sync_from and bucket replication policy do
complicate this picture, i think this concept of residency and
redirects are important to make sense of s3's LocationConstraint. but
perhaps the sync policy model could be extended to take over the
zonegroup's role here?
Both "sync_from" and sync policy could be
moved up to realm level while the isolation of datasets can still be maintained. On the
other hand, if some new features are introduced to enable some isolation of metadata
within the same realm, probably at zonegroup level, its usefulness may be more
justified.> Regards,Yixin
On Friday, June 30, 2023 at 11:29:16 a.m. EDT, Casey Bodley
<cbodley(a)redhat.com> wrote:
you're correct that the distinction is between metadata and data;
metadata like users and buckets will replicate to all zonegroups,
while object data only replicates within a single zonegroup. any given
bucket is 'owned' by the zonegroup that creates it (or overridden by
the LocationConstraint on creation). requests for data in that bucket
sent to other zonegroups should redirect to the zonegroup where it
resides
the ability to create multiple zonegroups can be useful in cases where
you want some isolation for the datasets, but a shared namespace of
users and buckets. you may have several connected sites sharing
storage, but only require a single backup for purposes of disaster
recovery. there it could make sense to create several zonegroups with
only two zones each to avoid replicating all objects to all zones
in other cases, it could make more sense to isolate things in separate
realms with a single zonegroup each. zonegroups just provide some
flexibility to control the isolation of data and metadata separately
On Thu, Jun 29, 2023 at 5:48 PM Yixin Jin <yjin77(a)yahoo.ca> wrote:
Hi folks,
In the multisite environment, we can get one realm that contains multiple zonegroups,
each in turn can have multiple zones. However, the purpose of zonegroup isn't clear to
me. It seems that when a user is created, its metadata is synced to all zones within the
same realm, regardless whether they are in different zonegroups or not. The same happens
to buckets. Therefore, what is the purpose of having zonegroups? Wouldn't it be easier
to just have realm and zones?
Thanks,Yixin
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