Thanks Alfredo. Just to clear that My configuration has 5 OSD's (7200 rpm SAS HDDS) which are slower than the 200G SSD. Thats why I asked for a 10G WAL partition for each OSD on the SSD.
Are you asking us to do 40GB * 5 partitions on SSD just for block.db?
On Fri, Sep 7, 2018 at 5:36 PM Alfredo Deza <adeza@xxxxxxxxxx> wrote:
On Fri, Sep 7, 2018 at 8:27 AM, Muhammad Junaid <junaid.fsd.pk@xxxxxxxxx> wrote:
> Hi there
>
> Asking the questions as a newbie. May be asked a number of times before by
> many but sorry, it is not clear yet to me.
>
> 1. The WAL device is just like journaling device used before bluestore. And
> CEPH confirms Write to client after writing to it (Before actual write to
> primary device)?
>
> 2. If we have lets say 5 OSD's (4 TB SAS) and 1 200GB SSD. Should we
> partition SSD in 10 partitions? Shoud/Can we set WAL Partition Size against
> each OSD as 10GB? Or what min/max we should set for WAL Partition? And can
> we set remaining 150GB as (30GB * 5) for 5 db partitions for all OSD's?
A WAL partition would only help if you have a device faster than the
SSD where the block.db would go.
We recently updated our sizing recommendations for block.db at least
4% of the size of block (also referenced as the data device):
http://docs.ceph.com/docs/master/rados/configuration/bluestore-config-ref/#sizing
In your case, what you want is to create 5 logical volumes from your
200GB at 40GB each, without a need for a WAL device.
>
> Thanks in advance. Regards.
>
> Muhammad Junaid
>
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