28 Apr
2020
28 Apr
'20
4:27 a.m.
On Thu, Apr 23, 2020 at 11:05 PM <jesper(a)krogh.cc> wrote:
Hi
We have an 3 year old Hadoop cluster - up for refresh - so it is time
to evaluate options. The "only" usecase is running an HBase installation
which is important for us and migrating out of HBase would be a hazzle.
Our Ceph usage has expanded and in general - we really like what we see.
Thus - Can this be "sanely" consolidated somehow? I have seen this:
https://docs.ceph.com/docs/jewel/cephfs/hadoop/
But it seem really-really bogus to me.
It recommends that you set:
pool 3 'hadoop1' rep size 1 min_size 1
Which would - if I understand correct - be disastrous. The Hadoop end would
replicated in 3 across - but within Ceph the replication would be 1.
The 1 replication in ceph means pulling the OSD node would "gaurantee" the
pg's to go inactive - which could be ok - but there is nothing
gauranteeing that the other Hadoop replicas are not served out of the same
OSD-node/pg? In which case - rebooting an OSD node would bring the hadoop
cluster unavailable.
I just want to affirm that you are correct about this — this isn't a
good way to go. I'm not quite sure how it happened, and the
CephFS/Hadoop interfaces are not really maintained at this point. :(
It seems like it ought to be a good fit but usage has always been too
low to justify maintaining it since we aren't Hadoop experts ourselves
and they made clear they were trying to prune rather than add new FS
implementations in-tree.
As mentioned elsewhere in the thread, the usage being pushed by
support companies and the users I know if is through RGW and the S3A
adapter (or I think maybe there's a newer one now?).
-Greg
Is anyone serving HBase out of Ceph - how does the stadck and
configuration look? If I went for 3 x replication in both Ceph and HDFS
then it would definately work, but 9x copies of the dataset is a bit more
than what looks feasible at the moment.
Thanks for your reflections/input.
Jesper
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