[posted & mailed] Lars Marowsky-Bree wrote: > > Wow... I hope that one of the maintainers will comment on this, I didn't > > even know that XP had a sw RAID implementation. Up to 100% more on read > > and 60% more on write is quite a significant margin. Is there anything > > in favour of the md driver if this is true? > > I've not really checked these numbers yet, so take the following with a grain > of salt. Have a look at http://www.hpl.hp.com/techreports/2002/HPL-2002-352.pdf - that'll tell you were the figures are from - the 100% is worst-case. > However, with RAID1 for example, I got approximately twice the read speed and > 95% of the write speed (compared to just using a single disk). One thing I forgot to mention in my post is that this is all (AFAICS) RAID0. > I have a really hard time imagining a 100% read boost; that would simply > exceed disk bandwidth, and 60% writes - how should that work? The md driver seriously underperforms at certain request sizes, and is generally underperforming. The average boost is less, but still about 40-60% read and 30-40% write. XP's RAID0 is better than JBOD above a certain request size, which is pretty good. > I'm not claiming md is perfect or the fastest imaginable solution, but it is > rather close to theoretical disk bandwidth. A two digit percentage performance > improvement just can't be done. Well, that's why I asked in my original post for people to look at the report. Is isn't that long and it's pretty clear (although short on config details). -- Illtud Daniel illtud.daniel@llgc.org.uk Uwch Ddadansoddwr Systemau Senior Systems Analyst Llyfrgell Genedlaethol Cymru National Library of Wales Yn siarad drosof fy hun, nid LlGC - Speaking personally, not for NLW - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
