Re: DPI_SPACE query after extending pool
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Wang, Di
Hello Chunk
That is strange. According the output of dmg pool query, 83 objects were deleted after extend, so some space should be reclaimed.
“dmg pool query kiddie ……… Rebuild done, 83 objs, 0 recs “
before extend: s_total(30000021504,470000000000) s_free(29994849224,434968621056) after extend: s_total(60000043008,940000000000) s_free(59994841512,869937672192)
Hmm It seems SCM is ok, only NVME space are doubled after extend. If you do not see NVME free space get back after a few mins, probably need create a ticket.
Thanks WangDi
On 6/1/22, 10:56 AM, "daos@daos.groups.io on behalf of Tuffli, Chuck" <daos@daos.groups.io on behalf of chuck.tuffli@...> wrote:
Wangdi
When I checked this morning, the pool had been idle four days, but the values from daos_pool_query() have not changed.
As for object class, I'm not sure. Pool creation didn't specify a class. Here is the container query output: # daos cont query ERROR: daos: pool and container ID must be specified if --path not used ]# daos cont query kiddie whiz Container UUID : 5c61770a-2b56-4922-b95b-d025fa4d0527 Container Label : whiz Container Type : POSIX Pool UUID : 700bf1b6-38b8-467e-9f91-7131138210ba Number of snapshots : 0 Latest Persistent Snapshot : 0x0 Container redundancy factor: 0 Object Class : UNKNOWN Chunk Size : 1.0 MiB
From: daos@daos.groups.io <daos@daos.groups.io> on behalf of Wang, Di <di.wang@...>
Hello Chuck
Pool extend might migrate the data to the new pool target, then the original data will be delete asynchronous, so those space might be reclaimed a few mins later if the system is not busy.
You probably should do your daos_pool_query() a bit later. Btw: what are those objects class in your pool?
Thanks Wangdi
On 5/25/22, 2:54 PM, "daos@daos.groups.io on behalf of Tuffli, Chuck" <daos@daos.groups.io on behalf of chuck.tuffli@...> wrote:
# dmg pool query kiddie Pool 700bf1b6-38b8-467e-9f91-7131138210ba, ntarget=32, disabled=0, leader=0, version=18 Pool space info: - Target(VOS) count:32 - Storage tier 0 (SCM): Total size: 60 GB Free: 60 GB, min:1.9 GB, max:1.9 GB, mean:1.9 GB - Storage tier 1 (NVMe): Total size: 940 GB Free: 870 GB, min:27 GB, max:27 GB, mean:27 GB Rebuild done, 83 objs, 0 recs From: daos@daos.groups.io <daos@daos.groups.io> on behalf of Nabarro, Tom <tom.nabarro@...>
Hello Chuck,
Could you please run `dmg pool query` on the pool and show the results, this will give you a bit more info on pool usage.
Regards, Tom
From: daos@daos.groups.io <daos@daos.groups.io>
On Behalf Of Tuffli, Chuck
I've been experimenting with extending a pool but don't quite understand the results. Any insights would be most appreciated.
The cluster is running with DAOS v2.0.2 and consists of a client and a pair of servers/storage nodes. To simulate adding a server to the cluster, I created a pool by specifying the ranks associated with one of the servers. I.e.: # dmg system query --verbose Rank UUID Control Address Fault Domain State Reason ---- ---- --------------- ------------ ----- ------ 0 654345f9-249c-48b1-b6dc-ec08dbf2aded x.150.0.3:10001 /d006 Joined 1 b384771a-ddbc-491a-8807-8d86544d7c2f x.150.0.4:10001 /d010 Joined 2 01c672cf-3365-476f-87ec-41a15a44e946 x.150.0.4:10001 /d010 Joined 3 93a8d382-b970-408a-9c21-e01c35265e77 x.150.0.3:10001 /d006 Joined # dmg pool create --ranks=0,3 --size=500G kiddie
I used the pool extend command to simulate adding a server: # dmg pool extend --ranks=1,2 kiddie
My application queried the pool size before and after the extension using daos_pool_query( ... DPI_SPACE ...). The numbers below are the info.pi_space.ps_space values for (DAOS_MEDIA_SCM, DAOS_MEDIA_NVME). before extend: s_total(30000021504,470000000000) s_free(29994849224,434968621056) after extend: s_total(60000043008,940000000000) s_free(59994841512,869937672192)
The total pool sized doubled (good), but the used space (i.e., s_total - s_free) also doubled. Naively, I expected the used space to remain the same as the pool has a redundancy factor of zero. Doing some arithmetic on the above works out to the used space being 35.036 GB before the expansion and 70.068 GB after. Note that, for the moment, I'm choosing to ignore that the used size is several orders of magnitude bigger that the data written (~600 KB).
Where did I goof in this methodology? TIA.
--chuck
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