On Mon, 13 Apr 2015 10:39:57 +0530 Sanjoy Dasgupta wrote: > Hi! > > This is an often discussed and clarified topic, but Reason why I am > asking is because > > If We use a RAID controller with Lot of Cache (FBWC) and Configure each > Drive as Single Drive RAID0, then Write to disks will benefit by using > FBWC and accelerate I/O performance. Is this correct assumption ? > In the case of Ceph, the journal writes (assuming journals on the HDDs, not separate SSDs) will benefit from this indeed. > Also, it indeed helps, what are the downside of using RAID Controller > with Cache in above manner (Apart from Cost of RAID controller) ? > If you have too much money or existing HW, knock yourself out. ^.^ Aside from the cost, the cache should be battery backed, additional costs and maintenance issues. Setting up RAID0 drives can be painful (megacli must die), and adds another step to OSD replacement/deployment. The resulting drive may or may not have all SMART features exposed and (not applicable in your case) won't support TRIM. Lastly the cache tends to be small when shared with many HDDs and there is also competition over it by reads and writes, but that's something to keep in mind, not a disadvantage per se. Christian -- Christian Balzer Network/Systems Engineer chibi@xxxxxxx Global OnLine Japan/Fusion Communications http://www.gol.com/ _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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