Hi Caspar,
Thanx. I don't see any mention that it's a bad idea to have the WAL and DB on the same SSD, but I guess it could improve performance?
I do understand that if I loose the the WAL drive, I loose the OSD's as well.
From what I gather, I can't move the WAL or DB devices and would have to completely rebuild the OSD storage. So, unless there's a compelling reason not to have those two on the same drive
On Thu, Nov 23, 2017 at 11:53 AM, Caspar Smit <casparsmit@xxxxxxxxxxx> wrote:
Rudi,First off all do not deploy an OSD specifying the same seperate device for DB and WAL:
Please read the following why:
http://docs.ceph.com/docs/master/rados/configuration/ bluestore-config-ref/
That said you have a fairly large amount of SSD size available so i recommend using it as block.db:
You can specify a fixed size block.db size in ceph.conf using:
[global]
bluestore_block_db_size = 16106127360
The above is a 15GB block.db size
Now when you deploy an OSD with a seperate block.db device the partition will be 15GB.
The default size is a percentage of the device i believe and not always a usable amount.CasparMet vriendelijke groet,
Caspar Smit
Systemengineer
SuperNAS
Dorsvlegelstraat 13
1445 PA Purmerend
t: (+31) 299 410 414
e: casparsmit@xxxxxxxxxxx
w: www.supernas.eu2017-11-23 10:27 GMT+01:00 Rudi Ahlers <rudiahlers@xxxxxxxxx>:______________________________Hi,Can someone please explain this to me in layman's terms. How big a WAL drive do I really need?I have a 2x 400GB SSD drives used as WAL / DB drive and 4x 8TB HDD's used as OSD's. When I look at the drive partitions the DB / WAL partitions are only 576Mb & 1GB respectively. This feels a bit small.root@virt1:~# lsblkNAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTsda 8:0 0 7.3T 0 disk├─sda1 8:1 0 100M 0 part /var/lib/ceph/osd/ceph-0└─sda2 8:2 0 7.3T 0 partsdb 8:16 0 7.3T 0 disk├─sdb1 8:17 0 100M 0 part /var/lib/ceph/osd/ceph-1└─sdb2 8:18 0 7.3T 0 partsdc 8:32 0 7.3T 0 disk├─sdc1 8:33 0 100M 0 part /var/lib/ceph/osd/ceph-2└─sdc2 8:34 0 7.3T 0 partsdd 8:48 0 7.3T 0 disk├─sdd1 8:49 0 100M 0 part /var/lib/ceph/osd/ceph-3└─sdd2 8:50 0 7.3T 0 partsde 8:64 0 372.6G 0 disk├─sde1 8:65 0 1G 0 part├─sde2 8:66 0 576M 0 part├─sde3 8:67 0 1G 0 part└─sde4 8:68 0 576M 0 partsdf 8:80 0 372.6G 0 disk├─sdf1 8:81 0 1G 0 part├─sdf2 8:82 0 576M 0 part├─sdf3 8:83 0 1G 0 part└─sdf4 8:84 0 576M 0 partsdg 8:96 0 118G 0 disk├─sdg1 8:97 0 1M 0 part├─sdg2 8:98 0 256M 0 part /boot/efi└─sdg3 8:99 0 117.8G 0 part├─pve-swap 253:0 0 8G 0 lvm [SWAP]├─pve-root 253:1 0 29.3G 0 lvm /├─pve-data_tmeta 253:2 0 68M 0 lvm│ └─pve-data 253:4 0 65.9G 0 lvm└─pve-data_tdata 253:3 0 65.9G 0 lvm└─pve-data 253:4 0 65.9G 0 lvm--
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