Hi,
I have been doing some tests with rados bench write on a EC storage
pool with a writeback cache pool(replicated, size 3), and have some
questions:
* I had set target_max_bytes to 280G, and after some time of writing,
the cache pool stays filled around 250G of data, rados df output:
pool name category KB objects clones
degraded unfound rd rd KB wr
wr KB
cache - 244371669 60685 0
0 0 0 0 3521019
7329726464
data - 0 0 0
0 0 0 0 0
0
ecdata - 7211409408 1760598 0
0 0 0 0 1760598
7211409408
metadata - 2 20 0
0 0 0 0 21
8
total used 11019283916 1821303
total avail 83093579980
total space 94112863896
I thought target_max_bytes was raw bytes in the cache pool, but I
suppose it is the actual data then ? (I did not find this in the docs)
. So the cache pool will fill up to about 3*280G?
* Another question about that rados df output: There are no reads on
the cache pool, but of course there are when data gets evicted to the
ecdata pool. I guess this is just not taken into account for the rados
df output?
* After the rados test has been done, rados starts to cleanup the
written data. I see that it then reads data from the ecdata pool (is
this for verification?) but it is not read from the cache:
pool name category KB objects clones
degraded unfound rd rd KB wr
wr KB
cache - 147251372 2975965 0
0 0 1 1 8976363
12472766465
data - 0 0 0
0 0 0 0 0
0
ecdata - 9528655873 2326333 0
0 0 2919104 0 3763883
12472758273
metadata - 2 20 0
0 0 0 0 21
8
total used 16216299992 5302318
total avail 77896563904
total space 94112863896
Is this normal behaviour?
Thanks !!
Kenneth
