[PVE-User] Ceph: Some trouble creating OSD with journal on a sotware raid device...
gaio at sv.lnf.it
Thu Oct 13 14:30:46 CEST 2016
Mandi! Alwin Antreich
In chel di` si favelave...
> The ratio for SDD journal to OSD disks, can be done by a simple dd test. Take the write speed of the SSD and divide it
> through the write speed of the OSD, then you will get the max number of disks that can be used on one SSD, without
> expecting the SSD to be the bottleneck.
Wow! Good rule of thumb!
> > So i'm using (software) raid1, confident enought that the penalty of
> > the raid cannot impact so much overral.
> As in the text above, I wouldn't recommend adding another layer in between. Makes harder to troubleshoot.
Probably it is because i'm used to software raid, but seems to me not
really more ''complex''.
I've found also:
but seems old, probably some things changed... anyway it is true:
putting SO and the journals on the same SSD is not a optimal solution.
Also, raid-1 ''double'' the writes.
> You can use files as journal disks, but if recall right, then there was a thread on the ceph mailing list discussing
> this and its limitations.
Anyway seems that jornal on files is not supported, at least by
root at vedovanera:~# pveceph createosd /dev/sdb --journal_dev /mnt/journal/sdb
got unusual device path '/mnt/journal/sdb'
dott. Marco Gaiarin GNUPG Key ID: 240A3D66
Associazione ``La Nostra Famiglia'' http://www.lanostrafamiglia.it/
Polo FVG - Via della Bontà, 7 - 33078 - San Vito al Tagliamento (PN)
marco.gaiarin(at)lanostrafamiglia.it t +39-0434-842711 f +39-0434-842797
Dona il 5 PER MILLE a LA NOSTRA FAMIGLIA!
(cf 00307430132, categoria ONLUS oppure RICERCA SANITARIA)
More information about the pve-user