Le 04/09/2019 à 11:01, Lars Täuber a écrit :
Wed, 4 Sep 2019 10:32:56 +0200
Yoann Moulin <yoann.moulin(a)epfl.ch> ==> ceph-users(a)ceph.io :
Hello,
Tue, 3 Sep 2019 11:28:20 +0200
Yoann Moulin <yoann.moulin(a)epfl.ch> ==> ceph-users(a)ceph.io :
Is it better to put all WAL on one SSD and all
DBs on the other one? Or put WAL and DB of the first 5 OSDs on the first SSD and the 5
others on
the second one.
I don't know if this has a relevant impact on the latency/speed of the ceph system
but we use LVM on top of a SW RAID 1 over two SSDs for WAL & DB on this RAID1.
What is the recommended size for wall and db in my case?
I have :
10x 6TB Disk OSDs (data)
2x 480G SSD
Best,
I'm still unsure with the size of the block.db and the wal.
This seems to be relevant:
http://lists.ceph.com/pipermail/ceph-users-ceph.com/2019-May/035086.html
But it is also said that the pure WAL need just 1 GB of space.
http://lists.ceph.com/pipermail/ceph-users-ceph.com/2019-August/036509.html
So the conclusion would be to use 2*X(DB) + 1GB (WAL) if you put both on the same
partition/LV.
With X being on of 3GB, 30GB or 300GB.
You have 10 OSDs. That means you should have 10 partitions/LVs for DBs & WALs.
So, I don't have enough space on SSDs to do raid1, I must use 1 SSD for 5 disks.
5x64GB + 5x2GB should be good, shouldn't it?
And I still don't know if the ceph-ansible playbook can manage the LVM setup of shall
I need to prepare all VG and LV before.
Best,
--
Yoann Moulin
EPFL IC-IT