Am 10.02.2015 um 09:08 schrieb Mark Kirkwood:
On 10/02/15 20:40, Thomas Güttler wrote:
Hi,
does the lack of a battery backed cache in Ceph introduce any
disadvantages?
We use PostgreSQL and our servers have UPS.
But I want to survive a power outage, although it is unlikely. But "hope
is not an option ..."
You can certainly make use of adapter cards that have a battery backed cache with Ceph - either using RAID as usual or
creating arrays of "RAID 0 of 1 disk" that enable you to use the nice battery backed cache + writeback options on the
card and still have a "1 osd mapped to 1 disk" topology.
Without such cards it is still quite possible to have a power loss safe setup. These days (with reasonably modern 3.*
kernels) using SATA or SAS plus mount options that do *not* disable write barriers will leave you with a consistent,
safe state in the advent of power loss. You might want to test your SATA disk of choice to be sure, but SAS should be safe!
Thank you very much for the clarification.
Regards,
Thomas Güttler
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