On 8 September 2017 at 12:13, Valeri Galtsev <galtsev at kicp.uchicago.edu> wrote: > > On Fri, September 8, 2017 11:07 am, Stephen John Smoogen wrote: >> On 8 September 2017 at 11:00, Valeri Galtsev <galtsev at kicp.uchicago.edu> >> wrote: >>> >>> On Fri, September 8, 2017 9:48 am, hw wrote: >>>> m.roth at 5-cent.us wrote: >>>>> hw wrote: >>>>>> Mark Haney wrote: >>>>> <snip> >>>>>>> BTRFS isn't going to impact I/O any more significantly than, say, >>>>>>> XFS. >>>>>> >>>>>> But mdadm does, the impact is severe. I know there are ppl saying >>>>>> otherwise, but I´ve seen the impact myself, and I definitely >>>>>> don´t >>>>>> want >>>>>> it on that particular server because it would likely interfere with >>>>>> other services. >>>>> <snip> >>>>> I haven't really been following this thread, but if your requirements >>>>> are >>>>> that heavy, you're past the point that you need to spring some money >>>>> and >>>>> buy hardware RAID cards, like LSI, er, Avago, I mean, who's bought >>>>> them >>>>> more recently? >>>> >>>> Heavy requirements are not required for the impact of md-RAID to be >>>> noticeable. >>>> >>>> Hardware RAID is already in place, but the SSDs are "extra" and, as I >>>> said, >>>> not suited to be used with hardware RAID. >>> >>> Could someone, please, elaborate on the statement that "SSDs are not >>> suitable for hardware RAID". >>> >> >> It will depend on the type of SSD and the type of hardware RAID. There >> are at least 4 different classes of SSD drives with different levels >> of cache, write/read performance, number of lifetime writes, etc. >> There are also multiple types of hardware RAID. A lot of hardware RAID >> will try to even out disk usage in different ways. This means 'moving' >> the heavily used data from slow parts to fast parts etc etc. > > Wow, you learn something every day ;-) Which hardware RAIDs do these > moving of data (manufacturer/model, please - believe it or not I never > heard of that ;-). And "slow part" and "fast part" of what are data being > moved between? > > Thanks in advance for tutorial! > I thought it was HP who had these, but I can't find it.. which means without references... I get an F. My apologies on that. Thank you for keeping me honest. -- Stephen J Smoogen.