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Indeed it makes sense, thanks !
And so, just for my own thinking, for the implementation of a new
Bluestore project, we really have to ask ourselves the question of
whether separating WAL/DBs significantly increases performance. If
the WAL/DB are on the same device as the bluestore data device, we
only lose one OSD at a time...
Can we find recent benchmarks on this performance issue related to
the location of WAL/DBs ?
Thanks,
Hervé
Le 01/03/2018 à 16:31, David Turner a écrit :
This
aspect of osds has not changed from filestore with SSD journals to
bluestore with DB and WAL soon SSDs. If the SSD fails, all osds
using it aren't lost and need to be removed from the cluster and
recreated with a new drive.
You can never guarantee data integrity on bluestore or
filestore if any media of the osd fails completely.
Hello,
With Bluestore, I have a couple of questions regarding the
case of
separate partitions for block.wal and block.db.
Let's take the case of an OSD node that contains several
OSDs (HDDs) and
also contains one SSD drive for storing WAL partitions and
an another
one for storing DB partitions. In this configuration, from
my
understanding (but I may be wrong), each SSD drive appears
as a SPOF for
the entire node.
For example, what happens if one of the 2 SSD drives crashes
(I know,
it's very rare but...) ?
In this case, are the bluestore data on all the OSDs of the
same node
also lost ?
I guess so, but as a result, what is the recovery scenario ?
Will it be
necessary to entirely recreate the node (OSDs + block.wal +
block.db) to
rebuild all the replicas from the other nodes on it ?
Thanks in advance,
Hervé
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