thebestvibedev/tromcho.net
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Add documentation and a very basic test for pool management commands

Browse Source
This commit is contained in:
Vitaliy Filippov
2024-02-28 13:08:04 +03:00
parent 86243b7101
commit 4eab26f968
11 changed files with 258 additions and 38 deletions
Download Patch File Download Diff File Expand all files Collapse all files
docs/config/pool.en.md
+21 -4
View File
@@ -154,8 +154,25 @@ That is, if it becomes impossible to place PG data on at least (pg_minsize)
OSDs, PG is deactivated for both read and write. So you know that a fresh
write always goes to at least (pg_minsize) OSDs (disks).
That is, pg_size minus pg_minsize sets the number of disk failures to tolerate
without temporary downtime (for [osd_out_time](monitor.en.md#osd_out_time)).
For example, the difference between pg_minsize 2 and 1 in a 3-way replicated
pool (pg_size=3) is:
- If 2 hosts go down with pg_minsize=2, the pool becomes inactive and remains
inactive for [osd_out_time](monitor.en.md#osd_out_time) (10 minutes). After
this timeout, the monitor selects replacement hosts/OSDs and the pool comes
up and starts to heal. Therefore, if you don't have replacement OSDs, i.e.
if you only have 3 hosts with OSDs and 2 of them are down, the pool remains
inactive until you add or return at least 1 host (or change failure_domain
to "osd").
- If 2 hosts go down with pg_minsize=1, the pool only experiences a short
I/O pause until the monitor notices that OSDs are down (5-10 seconds with
the default [etcd_report_interval](osd.en.md#etcd_report_interval)). After
this pause, I/O resumes, but new data is temporarily written in only 1 copy.
Then, after osd_out_time, the monitor also selects replacement OSDs and the
pool starts to heal.
So, pg_minsize regulates the number of failures that a pool can tolerate
without temporary downtime for [osd_out_time](monitor.en.md#osd_out_time),
but at a cost of slightly reduced storage reliability.
FIXME: pg_minsize behaviour may be changed in the future to only make PGs
read-only instead of deactivating them.
@@ -168,8 +185,8 @@ read-only instead of deactivating them.
Number of PGs for this pool. The value should be big enough for the monitor /
LP solver to be able to optimize data placement.
"Enough" is usually around 64-128 PGs per OSD, i.e. you set pg_count for pool
to (total OSD count * 100 / pg_size). You can round it to the closest power of 2,
"Enough" is usually around 10-100 PGs per OSD, i.e. you set pg_count for pool
to (total OSD count * 10 / pg_size). You can round it to the closest power of 2,
because it makes it easier to reduce or increase PG count later by dividing or
multiplying it by 2.