Alain Fauconnet: > This page definitely is an excellent reference. If I may share my > experience here: we're progressively moving away from hardware RAID. > Most of our critical servers were IBM boxes, using IBM's ServeRAID h/w > RAID controller (ips). We've had more downtime with these than with > the boxes using kernel RAID: firmware bugs taking ages to be fixed, > drives suddenly seen as 'defunct' by the controller for no apparent > reason (they intensively tested OK on a non-RAID controller), very, > *very* little information about what's going on reported by the > controller and of course we were locked into using IBM disks only (the > controller won't take anything else).
Same experience here. I have 2 IBM servers and when the controller decides a drive is defunct it will refuse to ever use it again. This happens randomly. I put that disk into the other server and it works flawlessly. So my job at the moment involves moving disks between the servers :) > Long before that, we had a bunch of Acer servers using the Mylex > DAC960. More or less the same story (except having to use only a > particular brand of disks). I have had several controllers die on me, which is very bad for the RAID state. Of course, the lack of cooling was probably contributing, but that only goes to show that it's another level of complexity that can go wrong. > Of course this is just an example. Other h/w RAID controllers might be > more reliable, more predictable, but so far I really trust kernel RAID > more. Also, no need to much about with non-tsl-packaged drivers, and special software. mdadm provides not only RAID creation and mangement, but also alerting when a drive fails. I've made a policy not to use hardware RAID on Linux servers. > I'd use h/w RAID only on machines with extremely high I/O bandwidth > requirements. I would like to show you a Norwegian benchmark of hardware and kernel software RAID: http://www.hwb.no/artikkel/15307 The words might not mean much to you, but take a look at the graphs. The SIL-controller is just a plain SATA-controller: no hardware RAID. The other controllers have hardware RAID, but are also tested using SW RAID. Reality may differ in special cases, but you shouldn't worry about performance.
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