On 12/27/2014 02:32 AM, Lindsay Mathieson wrote:
I see a lot of people mount their xfs osd's with nobarrier for extra performance, certainly it makes a huge difference to my small system. However I don't do it as my understanding is this runs a risk of data corruption in the event of power failure - this is the case, even with ceph? side note: How do I tell if my disk cache is battery backed? I have WD Red 3TB (WD30EFRX-68EUZN0) with 64M cache, but no mention of battery backup in the docs. I presume that means it isn't? :)
You should never use "nobarrier" for xfs or ext4 - we worked hard to make the difference negligible when the hardware has non-volatile caches, so it is easy to default to the safe, barrier enabled mode.
Getting the data safely to disk is complicated, even with a battery backed RAID card you can be exposed to data loss (if the actual drives have the write cache enabled and your HBA does not manage that appropriately).
Regards, Ric _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
