From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Priebe - Profihost AG Subject: Re: RBD fio Performance concerns Date: Thu, 22 Nov 2012 16:28:57 +0100 Message-ID: <50AE44B9.7070804@profihost.ag> References: <1e160089-914f-4227-afb8-33cfaf883cdb@mailpro> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail.profihost.ag ([85.158.179.208]:44062 "EHLO mail.profihost.ag" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965216Ab2KVT3G (ORCPT ); Thu, 22 Nov 2012 14:29:06 -0500 In-Reply-To: <1e160089-914f-4227-afb8-33cfaf883cdb@mailpro> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Alexandre DERUMIER Cc: ceph-devel , Mark Kampe , =?UTF-8?B?U8OpYmFzdGllbiBIYW4=?= , Mark Nelson 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= =2E >>> >>> Why is this an advantage? > > Well, if you are cpu limited, I don't think you can use all 8*35000io= ps 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 hard= ware problem, you'll lost your journal. But who cares? it's also on the 2nd node. or even on the 3rd if you hav= e=20 replicas 3. Stefan > ----- Mail original ----- > > De: "Stefan Priebe - Profihost AG" > =C3=80: "Mark Nelson" > Cc: "Alexandre DERUMIER" , "ceph-devel" , "Mark Kampe" , "S=C3=A9ba= stien Han" > Envoy=C3=A9: 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 noti= ng >> 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 D= isk > 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 pl= aying >>>> 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 wou= ld be >>> to be able to deaktivate the journal at all. But ceph does not supp= ort >>> 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 w= ith an >>>>> fs on it be better than tmpfs as we can use dio? >>>>> >>>>> Greets, >>>>> Stefan >>>>> >>>>>> ----- Mail original ----- >>>>>> >>>>>> De: "Stefan Priebe - Profihost AG" >>>>>> =C3=80: "S=C3=A9bastien Han" >>>>>> Cc: "Mark Nelson" , "Alexandre DERUMIER= " >>>>>> , "ceph-devel" = , >>>>>> "Mark Kampe" >>>>>> Envoy=C3=A9: Jeudi 22 Novembre 2012 14:29:03 >>>>>> Objet: Re: RBD fio Performance concerns >>>>>> >>>>>> Am 22.11.2012 14:22, schrieb S=C3=A9bastien Han: >>>>>>> And RAMDISK devices are too expensive. >>>>>>> >>>>>>> It would make sense in your infra, but yes they are really expe= nsive. >>>>>> >>>>>> We need something like tmpfs - running in local memory but suppo= rt >>>>>> dio. >>>>>> >>>>>> Stefan >>>>>> >>>> >>>> >> >> -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html