The document introduces cStor replica, which uses uZFS to create pool and block volumes in userspace and store ZIL records for replication. cStor pool is the logical entity of the uZFS pool, and cStor Volume Replica is the logical entity of the uZFS block volume. Configuring and performing I/O on uZFS volumes requires minimal code changes and interfacing with existing layers like DMU, ZIL and zrepl_prot for communication with targets.

1. Introduction to cStor replica
Oct 5th, 2018
VItta (vitta@mayadata.io)

2. storage pool
NVMe SSD SAS DisksHostDir SAN/NAS S3NVDIMM SSDs
K8s node
cStor Pool

3. Volume replica
NVMe SSD SAS DisksHostDir SAN/NAS S3NVDIMM SSDs
K8s node
cStor Pool
cStor volume replicas

4. cStor pool
consists of
- zrepl binary,
and,

5. zrepl
consists of uZFS, which can mean,
- micro ZFS
- ZFS in user space,
hmm..

6. uZFS
is based out of DMU layer of ZFS on
Linux,
and,
is in user space
makes sense?

7. uZFS
so, in uZFS, there is,
- creation of pool and block
volume (from DMU layer) in
userspace
- storing ZIL records
- and, replaying them

8. uZFS
This logical entity of
- pool is ‘cStor pool’, and,
- of block volume is ‘cStor
Volume Replica’

9. uZFS
but, how to configure it?
does ZFS on Linux’s zpool / zfs CLI
binaries works on this DMU layer of
….. ?

10. uZFS
zfs / zpool CLI binaries of ZFS of
Linux doesn’t work,
then, how?

11. uZFS
requirement#1
- minimal amount of code change
- easy to maintain
- being in sync with upstream
- configure uZFS

12. configuring uZFS
REST API server?
and, any other options?

13. configuring uZFS
will IOCTL redirection help?
but, what is it?

14. IOCTL redirection
zfs
zrepl
kernel
X X
unix domain
socket
uzfs code uzfs code zpool

15. configuring zrepl
cStor pool
zfs
zpool
zrepl
cStor pool mgmt
s
e
r
v
e
r

16. uZFS
but,
how to do read / write into uZFS?

17. uZFS
requirement#2
- minimal amount of code change
- easy to maintain
- being in sync with upstream
- write into uZFS block volume

18. IOs on uZFS
block volumes
(some kind of) API server?
and, then,
(PTO)

19. IOs on uZFS
block volumes
and then,
write into uZFS block volume from
DMU layer

20. zrepl
(continuation from slide 5)
and, so, it also consists of
- zrepl_prot layer to
communicate with target

21. cStor pool and target communication
cStor pool
istgt
zrepl
cStor istgt
zrepl_prot

22. Did you noticed
different colors of
lines in previous slide?

23. Thanks
&
See You Later