Re: HP9000+LVM+Online

David Chan (dwc@cix.compulink.co.uk) wrote: : Andy : I got the impression that Mike's system only had one chunk (therefore one : page cleaner) which was striped underneath using LVM. Note that LVM is This is nearly correct. During checkpoints there is indeed only one page cleaner due to the fact that there is only one chunk. Outside of checkpoints we use many (16) page cleaners and many (32) LRU queues to minimise LRU searching overhead while running with very low (15/25) MIN/MAX_DIRTY parameters. [observations about why LVM is fast clipped] Your explanations about the efficiency of this kind of LVM setup and how fast it is agree with mine and HP's. : The only thing I'm concerned about is that some LVM products don't do : synchronous writes i.e. it buffers them. If this is the case on HP then : beware, because a checkpoint would not actually write to disk. I cannot honestly remember here but I think it is synced. (Although we have not had a power fail yet to prove the conjecture!) Mike.