Re: SSD Sizing for DB/WAL: 4% for large drives?

[Martin Verges <martin.verges@xxxxxxxx>]

Hello Jake,

do you have any latency requirements that you do require the DB/WAL at all?

If not, CephFS with EC on SATA HDD works quite well as long as you have the metadata on a separate ssd pool.

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Am Di., 28. Mai 2019 um 15:13 Uhr schrieb Jake Grimmett <jog@xxxxxxxxxxxxxxxxx>:

Dear All,

Quick question regarding SSD sizing for a DB/WAL...

I understand 4% is generally recommended for a DB/WAL.

Does this 4% continue for "large" 12TB drives, or can we  economise and
use a smaller DB/WAL?

Ideally I'd fit a smaller drive providing a 266GB DB/WAL per 12TB OSD,
rather than 480GB. i.e. 2.2% rather than 4%.

Will "bad things" happen as the OSD fills with a smaller DB/WAL?

By the way the cluster will mainly be providing CephFS, fairly large
files, and will use erasure encoding.

many thanks for any advice,

Jake


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