Path: utzoo!news-server.csri.toronto.edu!rpi!usc!elroy.jpl.nasa.gov!decwrl!pa.dec.com!rust.zso.dec.com!shlump.nac.dec.com!riscy.enet.dec.com!croton.nyo.dec.com!frank From: frank@croton.nyo.dec.com (Frank Wortner) Newsgroups: comp.unix.ultrix Subject: Re: Will prestoserve help a client Message-ID: <1973@riscy.enet.dec.com> Date: 18 Mar 91 15:24:52 GMT References: <1991Mar11.204258.29415@cunixf.cc.columbia.edu> Sender: newsdaemon@riscy.enet.dec.com Reply-To: frank@croton.nyo.dec.com (Frank Wortner) Organization: Digital Equipment Corporation Lines: 29 In article , pcg@test.aber.ac.uk (Piercarlo Antonio Grandi) writes: > Rethorical question: how many megabytes of extra disk buffer cache on > the client or server can you buy for the cost of one NFS accelerator? Buffer cache really doesn't fulfill the same function. Unless the cache is nonvolatile, a system crash will destroy any data that hasn't been flushed to disk. Since PrestoServe commits transactions to "stable storage," it can safely buffer transactions that normally can only use a buffer cache as a "write-through" cache, if they can use it at all. The other assumption you're making is that this is all done by expensive memory. If that were the case, it should be possible to simply increase the size of the buffer cache and watch disk performance go through the roof. If that was all, then someone would have surely discovered this by now. NFS accellerators also use sophisticated software to manage and control the cache. The cache itself is only half the story. The hardware/software combination is what makes the product. Frank