On Wed, Aug 7, 2019 at 12:08 AM Konstantin Shalygin <k0...@k0ste.ru> wrote:
> On 8/7/19 1:40 PM, Robert LeBlanc wrote:
>
> > Maybe it's the lateness of the day, but I'm not sure how to do that.
> > Do you have an example where all the OSDs are of class ssd?
> Can't parse what you mean. You always should paste your `ceph osd tree`
> first.
>
Our 'ceph osd tree' is like this:
ID CLASS WEIGHT TYPE NAME STATUS REWEIGHT PRI-AFF
-1 892.21326 root default
-3 69.16382 host sun-pcs01-osd01
0 ssd 3.49309 osd.0 up 1.00000 1.00000
1 ssd 3.42329 osd.1 up 0.87482 1.00000
2 ssd 3.49309 osd.2 up 0.88989 1.00000
3 ssd 3.42329 osd.3 up 0.94989 1.00000
4 ssd 3.49309 osd.4 up 0.93993 1.00000
5 ssd 3.42329 osd.5 up 1.00000 1.00000
6 ssd 3.49309 osd.6 up 0.89490 1.00000
7 ssd 3.42329 osd.7 up 1.00000 1.00000
8 ssd 3.49309 osd.8 up 0.89482 1.00000
9 ssd 3.42329 osd.9 up 1.00000 1.00000
100 ssd 3.49309 osd.100 up 1.00000 1.00000
101 ssd 3.42329 osd.101 up 1.00000 1.00000
102 ssd 3.49309 osd.102 up 1.00000 1.00000
103 ssd 3.42329 osd.103 up 0.81482 1.00000
104 ssd 3.49309 osd.104 up 0.87973 1.00000
105 ssd 3.42329 osd.105 up 0.86485 1.00000
106 ssd 3.49309 osd.106 up 0.79965 1.00000
107 ssd 3.42329 osd.107 up 1.00000 1.00000
108 ssd 3.49309 osd.108 up 1.00000 1.00000
109 ssd 3.42329 osd.109 up 1.00000 1.00000
-5 62.24744 host sun-pcs01-osd02
10 ssd 3.49309 osd.10 up 1.00000 1.00000
11 ssd 3.42329 osd.11 up 0.72473 1.00000
12 ssd 3.49309 osd.12 up 1.00000 1.00000
13 ssd 3.42329 osd.13 up 0.78979 1.00000
14 ssd 3.49309 osd.14 up 0.98961 1.00000
15 ssd 3.42329 osd.15 up 1.00000 1.00000
16 ssd 3.49309 osd.16 up 0.96495 1.00000
17 ssd 3.42329 osd.17 up 0.94994 1.00000
18 ssd 3.49309 osd.18 up 1.00000 1.00000
19 ssd 3.42329 osd.19 up 0.80481 1.00000
110 ssd 3.49309 osd.110 up 0.97998 1.00000
111 ssd 3.42329 osd.111 up 1.00000 1.00000
112 ssd 3.49309 osd.112 up 1.00000 1.00000
113 ssd 3.42329 osd.113 up 0.72974 1.00000
116 ssd 3.49309 osd.116 up 0.91992 1.00000
117 ssd 3.42329 osd.117 up 0.96997 1.00000
118 ssd 3.49309 osd.118 up 0.93959 1.00000
119 ssd 3.42329 osd.119 up 0.94481 1.00000
... plus 11 more hosts just like this
How do you single out one OSD from each host for the metadata only and
prevent data on that OSD when all the device classes are the same? It seems
that you would need one OSD to be a different class to do that. It a
previous email the conversation was:
Is it possible to add a new device class like 'metadata'?
Yes, but you don't need this. Just use your existing class with another
crush ruleset.
So, I'm trying to figure out how you use the existing class of 'ssd' with
another CRUSH ruleset to accomplish the above.
> > Yes, we can set quotas to limit space usage (or number objects), but
> > you can not reserve some space that other pools can't use. The problem
> > is if we set a quota for the CephFS data pool to the equivalent of 95%
> > there are at least two scenario that make that quota useless.
>
> Of course. 95% of CephFS deployments is where meta_pool on flash drives
> with enough space for this.
>
>
> ```
>
> pool 21 'fs_data' replicated size 3 min_size 2 crush_rule 4 object_hash
> rjenkins pg_num 64 pgp_num 64 last_change 56870 flags hashpspool
> stripe_width 0 application cephfs
> pool 22 'fs_meta' replicated size 3 min_size 2 crush_rule 0 object_hash
> rjenkins pg_num 16 pgp_num 16 last_change 56870 flags hashpspool
> stripe_width 0 application cephfs
>
> ```
>
> ```
>
> # ceph osd crush rule dump replicated_racks_nvme
> {
> "rule_id": 0,
> "rule_name": "replicated_racks_nvme",
> "ruleset": 0,
> "type": 1,
> "min_size": 1,
> "max_size": 10,
> "steps": [
> {
> "op": "take",
> "item": -44,
> "item_name": "default~nvme" <------------
> },
> {
> "op": "chooseleaf_firstn",
> "num": 0,
> "type": "rack"
> },
> {
> "op": "emit"
> }
> ]
> }
> ```
Yes, our HDD cluster is much like this, but not Luminous, so we created as
separate root with SSD OSD for the metadata and set up a CRUSH rule for the
metadata pool to be mapped to SSD. I understand that the CRUSH rule should
have a `step take default class ssd` which I don't see in your rule unless
the `~` in the item_name means device class.
Thanks
----------------
Robert LeBlanc
PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1
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