On 09/21/2017 03:17 AM, Dietmar Rieder wrote:
On 09/21/2017 09:45 AM, Maged Mokhtar wrote:
On 2017-09-21 07:56, Lazuardi Nasution wrote:
Hi,
I'm still looking for the answer of these questions. Maybe someone can
share their thought on these. Any comment will be helpful too.
Best regards,
On Sat, Sep 16, 2017 at 1:39 AM, Lazuardi Nasution
<mrxlazuardin@xxxxxxxxx <mailto:mrxlazuardin@xxxxxxxxx>> wrote:
Hi,
1. Is it possible configure use osd_data not as small partition on
OSD but a folder (ex. on root disk)? If yes, how to do that with
ceph-disk and any pros/cons of doing that?
2. Is WAL & DB size calculated based on OSD size or expected
throughput like on journal device of filestore? If no, what is the
default value and pro/cons of adjusting that?
3. Is partition alignment matter on Bluestore, including WAL & DB
if using separate device for them?
Best regards,
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I am also looking for recommendations on wal/db partition sizes. Some hints:
ceph-disk defaults used in case it does not find
bluestore_block_wal_size or bluestore_block_db_size in config file:
wal = 512MB
db = if bluestore_block_size (data size) is in config file it uses 1/100
of it else it uses 1G.
There is also a presentation by Sage back in March, see page 16:
https://www.slideshare.net/sageweil1/bluestore-a-new-storage-backend-for-ceph-one-year-in
wal: 512 MB
db: "a few" GB
the wal size is probably not debatable, it will be like a journal for
small block sizes which are constrained by iops hence 512 MB is more
than enough. Probably we will see more on the db size in the future.
This is what I understood so far.
I wonder if it makes sense to set the db size as big as possible and
divide entire db device is by the number of OSDs it will serve.
E.g. 10 OSDs / 1 NVME (800GB)
(800GB - 10x1GB wal ) / 10 = ~79Gb db size per OSD
Is this smart/stupid?
Personally I'd use 512MB-2GB for the WAL (larger buffers reduce write
amp but mean larger memtables and potentially higher overhead scanning
through memtables). 4x256MB buffers works pretty well, but it means
memory overhead too. Beyond that, I'd devote the entire rest of the
device to DB partitions.
Mark
Dietmar
--
_________________________________________
D i e t m a r R i e d e r, Mag.Dr.
Innsbruck Medical University
Biocenter - Division for Bioinformatics
Innrain 80, 6020 Innsbruck
Phone: +43 512 9003 71402
Fax: +43 512 9003 73100
Email: dietmar.rieder@xxxxxxxxxxx
Web: http://www.icbi.at
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