[ceph-users] Journal / WAL drive size?

Caspar Smit casparsmit at supernas.eu
Thu Nov 23 01:53:56 PST 2017


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.

Caspar

Met vriendelijke groet,

Caspar Smit
Systemengineer
SuperNAS
Dorsvlegelstraat 13
1445 PA Purmerend

t: (+31) 299 410 414
e: casparsmit at supernas.eu
w: www.supernas.eu

2017-11-23 10:27 GMT+01:00 Rudi Ahlers <rudiahlers at gmail.com>:

> 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 at virt1:~# lsblk
> NAME               MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
> sda                  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 part
> sdb                  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 part
> sdc                  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 part
> sdd                  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 part
> sde                  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 part
> sdf                  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 part
> sdg                  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
>
>
>
>
> --
> Kind Regards
> Rudi Ahlers
> Website: http://www.rudiahlers.co.za
>
> _______________________________________________
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> ceph-users at lists.ceph.com
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>
>
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