>>But who cares? it's also on the 2nd node. or even on the 3rd if you have >>replicas 3. Yes, but rebuilding a dead node use cpu and ios. (but it should be benched too, to see the impact on the production)
----- Mail original ----- De: "Stefan Priebe - Profihost AG" <[email protected]> À: "Alexandre DERUMIER" <[email protected]> Cc: "ceph-devel" <[email protected]>, "Mark Kampe" <[email protected]>, "Sébastien Han" <[email protected]>, "Mark Nelson" <[email protected]> Envoyé: Jeudi 22 Novembre 2012 16:28:57 Objet: Re: RBD fio Performance concerns Am 22.11.2012 16:26, schrieb Alexandre DERUMIER: >>> Haven't tested that. But does this makes sense? I mean data goes to Disk >>> journal - same disk then has to copy the Data from part A to part B. >>> >>> Why is this an advantage? > > Well, if you are cpu limited, I don't think you can use all 8*35000iops by > node. > So, maybe a benchmark can tell us if the difference is really big. > > Using tmpfs and ups can be ok, but if you have a kernel panic or hardware > problem, you'll lost your journal. But who cares? it's also on the 2nd node. or even on the 3rd if you have replicas 3. Stefan > ----- Mail original ----- > > De: "Stefan Priebe - Profihost AG" <[email protected]> > À: "Mark Nelson" <[email protected]> > Cc: "Alexandre DERUMIER" <[email protected]>, "ceph-devel" > <[email protected]>, "Mark Kampe" <[email protected]>, > "Sébastien Han" <[email protected]> > Envoyé: Jeudi 22 Novembre 2012 16:01:56 > Objet: Re: RBD fio Performance concerns > > Am 22.11.2012 15:46, schrieb Mark Nelson: >> I haven't played a whole lot with SSD only OSDs yet (other than noting >> last summer that iop performance wasn't as high as I wanted it). Is a >> second partition on the SSD for the journal not an option for you? > > Haven't tested that. But does this makes sense? I mean data goes to Disk > journal - same disk then has to copy the Data from part A to part B. > > Why is this an advantage? > > Stefan > >> Mark >> >> On 11/22/2012 08:42 AM, Stefan Priebe - Profihost AG wrote: >>> Am 22.11.2012 15:37, schrieb Mark Nelson: >>>> I don't think we recommend tmpfs at all for anything other than playing >>>> around. :) >>> >>> I discussed this with somebody frmo inktank. Had to search the >>> mailinglist. It might be OK if you're working with enough replicas and >>> UPS. >>> >>> I see no other option while working with SSDs - the only Option would be >>> to be able to deaktivate the journal at all. But ceph does not support >>> this. >>> >>> Stefan >>> >>>> On 11/22/2012 08:22 AM, Stefan Priebe - Profihost AG wrote: >>>>> Hi, >>>>> >>>>> can someone from inktank comment this? Might be using /dev/ram0 with an >>>>> fs on it be better than tmpfs as we can use dio? >>>>> >>>>> Greets, >>>>> Stefan >>>>> >>>>>> ----- Mail original ----- >>>>>> >>>>>> De: "Stefan Priebe - Profihost AG" <[email protected]> >>>>>> À: "Sébastien Han" <[email protected]> >>>>>> Cc: "Mark Nelson" <[email protected]>, "Alexandre DERUMIER" >>>>>> <[email protected]>, "ceph-devel" <[email protected]>, >>>>>> "Mark Kampe" <[email protected]> >>>>>> Envoyé: Jeudi 22 Novembre 2012 14:29:03 >>>>>> Objet: Re: RBD fio Performance concerns >>>>>> >>>>>> Am 22.11.2012 14:22, schrieb Sébastien Han: >>>>>>> And RAMDISK devices are too expensive. >>>>>>> >>>>>>> It would make sense in your infra, but yes they are really expensive. >>>>>> >>>>>> We need something like tmpfs - running in local memory but support >>>>>> dio. >>>>>> >>>>>> Stefan >>>>>> >>>> >>>> >> >> -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
