Hi, > Raid card for journal disks is Perc H730 (Megaraid), RAID 1, battery back > cache is on > > Default Cache Policy: WriteBack, ReadAdaptive, Direct, No Write Cache if Bad > BBU > Current Cache Policy: WriteBack, ReadAdaptive, Direct, No Write Cache if Bad > BBU > > I have 2 other nodes with older Perc H710 and similar SSDs with slightly > higher wear (6.3% vs 5.18%) but from observation they hardly hit 1.5 ms on > rear occasion > Cache, RAID, and battery situation is the same.
I would take a closer look at the RAID card. Are you sure the BBU is ok? In the past I noticed the Megaraid cards would do periodic battery tests that would completely drain the battery and thus disable the write cache until they reached some threshold of charge again. They also can do periodic "patrol reads" and "consistency checks" that can hurt performance. Or the card could just be failing, I have almost gone through more RAID cards than HDDs. The unreliability and black box nature of hardware RAID cards is one of the things that first got me looking into Ceph (although even mdadm is a big improvement in my opinion). For journals you are better off putting half your OSDs on one SSD and half on the other instead of RAID1. -Brendan _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
