Hello. I am intending to build a Ceph cluster using several Dell C6100 multi-node chassis servers. These have only 3 disk bays per node (12 x 3.5" drives across 4 nodes) so I can't afford to sacrifice a third of my capacity for SSDs. However, fitting the SSD via PCI-e seems a valid option. Unfortunately, I am not a storage/hardware guru, so I'm out of my depth regarding the valid types of SSDs - MLC vs SLC, read vs write optimized, internal caches and fault symmetries. Can you guide me on what to look for and suggest actual PCI-e products known to work properly in this role? Secondly, I'm unclear about how OSDs use the journal. It appears they write to the journal (in all cases, can't be turned off), ack to the client and then read the journal later to write to backing storage. Is that correct? I'm coming from enterprise ZFS with an SSD is also used for write journalling but data flushes are from the disk cache in memory, hence the use of write optimized SSDs. Why can't Ceph be configured to write from RAM instead of reading the journal on flush? Regards, Charles Sent from my BlackBerry® wireless handheld from Glo Mobile. _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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