> With 4 AGs this must represent the RAID6 or RAID10 case. Yes, the original RAID 6 case. >> Yes, in theory, a good cache controller should be able to sort this >> out. But at least this particular controller is not able to do so and >> could use a little help. > > Is the cache in write-through or write-back mode? The latter should > allow for aggressive reordering. The former none, or very little. And > is all of it dedicated to writes, or is it split? If split, dedicate it > all to writes. Linux is going to cache block reads anyway, so it makes > little sense to cache them in the controller as well. The cache is a write-back cache. Yes, it’s split 75% write / 25% read. Changing to 100% write does not make a difference. I can imagine that the small read cache might be beneficial for partial stripe writes, when the stripe contents from the untouched drives are in cache. >> Also, a single consumer-grade drive is >> certainly not helped by this write ordering. > > Are you referring to the Mushkin SSD I mentioned? No, I meant rotational storage. But even SSDs should gain at least a little from a linear write pattern. _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
