nice, anyone know if freebsd or netbsd or other o.s. have this (raid trim) to do some benchmarks without losing our time developing? 2011/6/29 Tom De Mulder <tdm27@xxxxxxxxx>: > On Wed, 29 Jun 2011, David Brown wrote: > >>> While you are mostly correct, over time even consumer SSDs will end up >>> in this state. >> >> I don't quite follow you here - what state will consumer SSDs end up in? > > Sorry, I meant to say "SSDs in typical consumer desktop machines". The state > where writes are very slow. > >> Have you tried any real-world benchmarking with realistic loads with a >> single SSD, ext4, and TRIM on and off? Almost every article I've seen on >> the subject is using very synthetic benchmarks, almost always on windows, >> few are done with current garbage-collecting SSDs. It seems to be accepted >> wisdom from the early days of SSDs that TRIM makes a big difference - and >> few people challenge that with real numbers or real thought, even though the >> internal structure of the flash has changed dramatically (transparent >> compression, for example, gives a completely different effect). >> >> Of course, if you /do/ try it yourself and can show clear figures, then >> I'm willing to change my mind :-) If I had a spare SSD, I'd do the testing >> myself. > > I have a set of 4 Intel 510 SSDs purely for testing, and I have used these > to simulate the kinds of workload I would expect them to experience in a > server environment (focused mainly on database access). So far, those tests > have focused on using single drives (ie. without RAID) on a variety of > controllers. > > Once the drives get fuller (something which does happen on servers) I do > indeed see write latencies that are in the order of several seconds (I saw > from 1500µs to 6000µs), as the drive suddenly struggles to free entire > blocks, where initially latency was in the single digits. > > I am hoping to get my hands on some Sandforce controller-based SSDs as well, > to compare, but even they show degradation as they get fuller in AnandTech's > tests (and those tests seem, IME, trustworthy). > > My current plan is to sacrifice half the capacity by partitioning, stick 2 > of them in md RAID1 (so, without TRIM) and over the next few days to run > benchmarks over them, to see what the end result is. > > > Best, > > -- > Tom De Mulder <tdm27@xxxxxxxxx> - Cambridge University Computing Service > +44 1223 3 31843 - New Museums Site, Pembroke Street, Cambridge CB2 3QH > -> 29/06/2011 : The Moon is Waning Crescent (18% of Full) -- Roberto Spadim Spadim Technology / SPAEmpresarial -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
