All compute resource backup servers and IS controllers within compute zone share the same distributed database (DDB).

It is tmpfs volume mounted at /onappstore/DB folder. The size of the database can be configured in /onappstore/onappstore.conf by changing parameter dbsize=256.

The database is created and populated with data during the IS startup process inside the SAMController service as shown below.


DDB is FS based data stored in folders as text files.

[FS_DB]  Datastore  Subdir

/onappstore/DB/Datastore: jdhbxnovc7zr86 /onappstore/DB/Datastore/jdhbxnovc7zr86: description   members   name   overcommit   replicas   sector_size   stripes   uuid   vdisks /onappstore/DB/Datastore/jdhbxnovc7zr86/members: 1308341613   1638717502   3789723832   3830220270   4284135282  976785243 /onappstore/DB/Datastore/jdhbxnovc7zr86/vdisks: awoeuctr854pmd   qksozqwm8yaji   l03obar8v249sz   n8k74ulq5my1w2  r6vpuag9l0syn4   t2sbe73qmki1du

[FS_DB] v2 Subdir

This folder contains information about vDisks in JSON format it also stores metadata about these files.
It is a new way of storing data inside DDB, but for now, it is only for snapshot information.
ls /onappstore/DB/v2/VDisk/
12kaws896bte4y.json 12kaws896bte4y.json.mtd 243zhavwnfb6pq.json 243zhavwnfb6pq.json.mtd q9c7ny6jfa842g.json q9c7ny6jfa842g.json.mtd


[FS_DB] locks Subdir


This folder holds locks for resources (nodes, data stores, vDisks, etc.) to prevent transaction interference and race conditions.
In general, operation files are not stored here for a long time. Accordingly, many files inside this folder may indicate problems or overload.
Locks are moved from /tmp folder to DB for better performance and reliability.


[FS_DB] Node Subdir

/onappstore/DB/Node:

1152875907   1308341613   1638717502   1855767384   3789723832 3830220270   4284135282   976785243

/onappstore/DB/Node/1308341613:

backupchannel   datastoremember   freespace   hbtl   hostid   ipaddr  lastping   model   nodestatus   performance   revision   serial   size   status utilization   uuid   vdisks   vendor   version

/onappstore/DB/Node/1308341613/vdisks:

awoeuctr854pmd   n8k74ulq5my1w2   t2sbe73qmki1du


[FS_DB]  VDisk  Subdir

/onappstore/DB/VDisk:

awoeuctr854pmd   qksozqwm8yaji   l03obar8v249sz   n8k74ulq5my1w2   r6vpuag9l0syn4  t2sbe73qmki1du

/onappstore/DB/VDisk/awoeuctr854pmd:

datastore   description   highest_gen_count   memberinfo   membership   name   replicas   sector_size  

sectors   snapshot   snapshots   st_mems   st_size   uuid

/onappstore/DB/VDisk/awoeuctr854pmd/memberinfo:

1308341613   1638717502   4284135282   976785243

/onappstore/DB/VDisk/awoeuctr854pmd/memberinfo/1308341613:

frontend   membership_gen_count   nodestatus   numkeys   port   seqno   snap_limit   st_mem   status

…..

/onappstore/DB/VDisk/awoeuctr854pmd/snapshots:

n8k74ulq5my1w2   t2sbe73qmki1du


DDB stores data about virtual objects used for IS configuration and management. Accordingly, tmpfs are stored in RAM, so we store persistent data at disks attached to IS:

  • Node metadata is stored at the node itself (file: STORAGENODE)

  • Datastore metadata is stored at its members (file: DS-<UUID>)

  • VDisk metadata stored at its members (file: vdisks/<UUID>.xml)

At startup, this persistent data is transfered to /onappstore/DB folder by the local update script. SD daemon syncs it within compute zone via the multicast channel. Syncs are periodical 120-sec timeout or at any metadata changing event like vDisk allocation or online.