On 07-05-2025 18:16, Anthony D'Atri wrote:
On May 7, 2025, at 5:06 AM, Janne Johansson <icepic.dz@xxxxxxxxx> wrote:
Den ons 7 maj 2025 kl 10:59 skrev Torkil Svensgaard <torkil@xxxxxxxx>:
We are looking at a cluster split between two DCs with the DCs as
failure domains.
Am I right in assuming that any recovery or backfill taking place should
largely happen inside each DC and not between them? Or can no such
assumptions be made?
Pools would be EC 4+8, if that matters.
Unless I am mistaken, the first/primary of each PG is the one "doing"
the backfills, so if the primaries are evenly distributed between the
sites, the source of all backfills would be in the remote DC in 50% of
the cases.
Are we talking about recovery, or backfill?
I was asking about both
I do not think the backfills are going to calculate how it can use
only "local" pieces to rebuild a missing/degraded PG piece without
going over the DC-DC link even if it is theoretically possible.
The LRC plugin might be able to localize *recovery*, but backfill from adding OSDs, changing CRUSH rules, etc. would always have to hit both.
Thanks both, I'll take a look at the LRC plugin.
Mvh.
Torkil
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Torkil Svensgaard
Sysadmin
MR-Forskningssektionen, afs. 714
DRCMR, Danish Research Centre for Magnetic Resonance
Hvidovre Hospital
Kettegård Allé 30
DK-2650 Hvidovre
Denmark
Tel: +45 386 22828
E-mail: torkil@xxxxxxxx
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