We noticed this degraded write performance too recently when the nearfull flag is present (cephfs kernel client, kernel 4.19.154). Appears to be due to forced synchronous writes when nearfull. https://github.com/ceph/ceph-client/blob/558b4510f622a3d96cf9d95050a04e7793d... https://tracker.ceph.com/issues/49406
It might be more accurate to say that the default nearfull is 85% for that reason, among others. Raising it will probably not get you enough storage to be worth the hassle.
On Tue, Apr 13, 2021 at 7:18 AM zp_8483 <zp_8483@163.com> wrote:
Backend:
XFS for the filestore back-end.
In our testing, we found the performance decreases when cluster usage exceed default nearfull ratio(85%), is it by design?
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