Hello,
still my test cluster with 0.94.6.
It's a bit fuzzy, but I don't think I saw this with Firefly, but then
again that is totally broken when it comes to cache tiers (switching
between writeback and forward mode).
goat is a cache pool for rbd:
---
# ceph osd pool ls detail
pool 2 'rbd' replicated size 3 min_size 1 crush_ruleset 2 object_hash rjenkins
pg_num 512 pgp_num 512 last_change 11729 lfor 11662 flags hashpspool tiers 9
read_tier 9 write_tier 9 stripe_width 0
pool 9 'goat' replicated size 1 min_size 1 crush_ruleset 3 object_hash rjenkins
pg_num 128 pgp_num 128 last_change 11730 flags hashpspool,incomplete_clones
tier_of 2 cache_mode writeback target_bytes 524288000 hit_set
bloom{false_positive_probability: 0.05, target_size: 0, seed: 0} 3600s x1
stripe_width 0
---
Initial state is this:
---
# rados df
pool name KB objects clones degraded
unfound rd rd KB wr wr KB
goat 34 429 0 0 0
1051 4182046 145803 10617422
rbd 164080702 40747 0 0 0
419664 71142697 4430922 531299267
total used 599461060 41176
total avail 5301740284
total space 5940328912
---
First we put some data in there with
"rados -p rbd bench 20 write -t 32 --no-cleanup"
which easily exceeds the target bytes of 512MB and gives us:
---
pool name KB objects
goat 356386 372
---
For starters, that's not the number I would have expected given how this
configured:
cache_target_dirty_ratio: 0.5
cache_target_full_ratio: 0.9
Lets ignore (but not forget) that discrepancy for now.
After doing a read with "rados -p rbd bench 20 rand -t 32" to my utter
bafflement I get:
---
pool name KB objects
goat 8226 199
---
And after a second read it's all gone, looking at the network traffic it
all originated from the base pool nodes and got relayed through the node
hosting the cache pool:
---
pool name KB objects
goat 34 191
---
I verified that the actual objects are on the base pool with 4MB each,
while their "copies" are on the cache pool OSDs with zero length.
Can anybody unbaffle me? ^o^
Christian
--
Christian Balzer Network/Systems Engineer
[email protected] Global OnLine Japan/Rakuten Communications
http://www.gol.com/
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