mirror of https://gitee.com/openkylin/qemu.git
a9db86b223
This patch adds single read pattern to quorum driver and quorum vote is default pattern. For now we do a quorum vote on all the reads, it is designed for unreliable underlying storage such as non-redundant NFS to make sure data integrity at the cost of the read performance. For some use cases as following: VM -------------- | | v v A B Both A and B has hardware raid storage to justify the data integrity on its own. So it would help performance if we do a single read instead of on all the nodes. Further, if we run VM on either of the storage node, we can make a local read request for better performance. This patch generalize the above 2 nodes case in the N nodes. That is, vm -> write to all the N nodes, read just one of them. If single read fails, we try to read next node in FIFO order specified by the startup command. The 2 nodes case is very similar to DRBD[1] though lack of auto-sync functionality in the single device/node failure for now. But compared with DRBD we still have some advantages over it: - Suppose we have 20 VMs running on one(assume A) of 2 nodes' DRBD backed storage. And if A crashes, we need to restart all the VMs on node B. But for practice case, we can't because B might not have enough resources to setup 20 VMs at once. So if we run our 20 VMs with quorum driver, and scatter the replicated images over the data center, we can very likely restart 20 VMs without any resource problem. After all, I think we can build a more powerful replicated image functionality on quorum and block jobs(block mirror) to meet various High Availibility needs. E.g, Enable single read pattern on 2 children, -drive driver=quorum,children.0.file.filename=0.qcow2,\ children.1.file.filename=1.qcow2,read-pattern=fifo,vote-threshold=1 [1] http://en.wikipedia.org/wiki/Distributed_Replicated_Block_Device [Dropped \n from an error_setg() error message --Stefan] Cc: Benoit Canet <benoit@irqsave.net> Cc: Eric Blake <eblake@redhat.com> Cc: Kevin Wolf <kwolf@redhat.com> Cc: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Liu Yuan <namei.unix@gmail.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> |
||
---|---|---|
.. | ||
Makefile.objs | ||
archipelago.c | ||
backup.c | ||
blkdebug.c | ||
blkverify.c | ||
bochs.c | ||
cloop.c | ||
commit.c | ||
cow.c | ||
curl.c | ||
dmg.c | ||
gluster.c | ||
iscsi.c | ||
linux-aio.c | ||
mirror.c | ||
nbd-client.c | ||
nbd-client.h | ||
nbd.c | ||
nfs.c | ||
parallels.c | ||
qapi.c | ||
qcow.c | ||
qcow2-cache.c | ||
qcow2-cluster.c | ||
qcow2-refcount.c | ||
qcow2-snapshot.c | ||
qcow2.c | ||
qcow2.h | ||
qed-check.c | ||
qed-cluster.c | ||
qed-gencb.c | ||
qed-l2-cache.c | ||
qed-table.c | ||
qed.c | ||
qed.h | ||
quorum.c | ||
raw-aio.h | ||
raw-posix.c | ||
raw-win32.c | ||
raw_bsd.c | ||
rbd.c | ||
sheepdog.c | ||
snapshot.c | ||
ssh.c | ||
stream.c | ||
vdi.c | ||
vhdx-endian.c | ||
vhdx-log.c | ||
vhdx.c | ||
vhdx.h | ||
vmdk.c | ||
vpc.c | ||
vvfat.c | ||
win32-aio.c |