Thank you all a lot for the answers!
From: este...@cloudera.com
Subject: Re: write availability
--
Cloudera, Inc.
On Tue, Apr 7, 2015 at 10:36 AM, Marcelo Valle (BLOOMBERG/ LONDON)
mvallemil...@bloomberg.net wrote:
Sorry, there is something I asked wrongly because I was understanding
, Marcelo Valle (BLOOMBERG/ LONDON)
mvallemil...@bloomberg.net wrote:
Thank you all a lot for the answers!
From: este...@cloudera.com
Subject: Re: write availability
--
Cloudera, Inc.
On Tue, Apr 7, 2015 at 10:36 AM, Marcelo Valle (BLOOMBERG/ LONDON)
mvallemil...@bloomberg.net wrote
the other nodes get up again?
Or I might get no write availability for a while?
Thanks Serega, it helps me to understand the differences.
From: user@hbase.apache.org
Subject: Re: write availability
If I have an application that writes to a HBase cluster, can I count that
the cluster will always available to receive writes?
No, it's CP, not AP system.
so everything get
that
the cluster will always available to receive writes?
I might not be able to read if a region server which handles a range of
keys is down, but will I be able to keep writing to other nodes, so
everything get in sync when the other nodes get up again?
Or I might get no write availability
to keep writing to other nodes, so
everything get in sync when the other nodes get up again?
Or I might get no write availability for a while?
hosting that
information go down and one of them come back, but with the disk intact?
Considering from the time they went down to the time it went back HBase
received new writes that would go to the same data node...
From: user@hbase.apache.org
Subject: Re: write availability
The data is stored
to the same data node...
From: user@hbase.apache.org
Subject: Re: write availability
The data is stored on files on hdfs. If a RS goes down, the master knows
which regions were on that RS and which hdfs files contain data for these
regions, so it will just assign the regions to others RS
come back, but with the
disk intact? Considering from the time they went down to the time it went
back HBase received new writes that would go to the same data node...
From: user@hbase.apache.org
Subject: Re: write availability
The data is stored on files on hdfs. If a RS goes down
come back, but with the
disk intact? Considering from the time they went down to the time it went
back HBase received new writes that would go to the same data node...
From: user@hbase.apache.org
Subject: Re: write availability
The data is stored on files on hdfs. If a RS goes down, the master
back again, but with the disk intact, with
all the data it had before crashing?
From: user@hbase.apache.org
Subject: Re: write availability
When a RS goes down, the Master will try to assign the regions on the remaining
RSes. When the RS comes back, after a while, the Master balancer process
new writes that would go to the same data node...
From: user@hbase.apache.org
Subject: Re: write availability
The data is stored on files on hdfs. If a RS goes down, the master knows
which regions were on that RS and which hdfs files contain data for these
regions, so it will just assign
will be written to
another region server? Another RS assumes the region range while the RS is
down?
What happens when the RS that was down goes up again?
From: user@hbase.apache.org
Subject: Re: write availability
I don’t know if I would say that…
I read Marcelo’s question
happens when the RS that was down goes up again?
From: user@hbase.apache.org
Subject: Re: write availability
I don’t know if I would say that…
I read Marcelo’s question of “if the cluster is up, even though a RS may be
down, can I still insert records in to HBase?”
So if the cluster is up
to the HBase cluster when
1 region server is down?
-Marcelo
From: Marcelo Valle (BLOOMBERG/ LONDON)
Subject: Re: write availability
Esteban,
If I understood correctly what you said:
For the failure mode you mention if all DNs go down (not the NN)
clients will be blocked waiting
From: Marcelo Valle (BLOOMBERG/ LONDON)
Subject: Re: write availability
Esteban,
If I understood correctly what you said:
For the failure mode you mention if all DNs go down (not the NN) clients
will be blocked waiting for the acknowledge of a write to the DNs and after
few retries the RS
. HBase provides other features like replication
which can even help you further on HA and other disaster recovery scenarios.
if you have more questions pelase let us know!
esteban.
-Marcelo
From: Marcelo Valle (BLOOMBERG/ LONDON)
Subject: Re: write availability
Esteban,
If I understood
and wouldn't be working for users
whose user id is in a down region (a region where all corresponding DNs are
down, considering 1 DN per RS). Is this right?
-Marcelo.
From: este...@cloudera.com
Subject: Re: write availability
Hello Marcelo,
HBase has strong durability guarantees to avoid data
: write availability
Hello Marcelo,
HBase has strong durability guarantees to avoid data loss. When a write
arrives to a RegionServer data will be persisted into a Write-Ahead-Log (on
HDFS) and temporarily in the RegionServer memory until the data from this
memory store is flushed (also
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