Interesting, I've been thinking about this and I think most Ceph installations could benefit from more nodes and less disks per node.
For example We have a replica level of 2, your RBD block size of 4mb. You start writing a file of 10gb, This is divided effectively into 4mb chunks, The first chunk to node 1 and node 2 (at the same time I assume) which is written to a journal then replayed to the data file system. Second chunk might be sent to node 2 and 3 at the same time which is written to a journal then replayed. (we now have overlap from chunk 1) Third chunk might be sent to 1 and 3 (we have more overlap from chunks 1 and 2) and as you can see this quickly this becomes an issue. So if we have 10 nodes vs. 3 nodes with the same mount of disks we should see better write and read performance as you would have less "overlap". Now we take BTRFS into the picture as I understand journals are not necessary due to the nature of the way it writes/snapshots and reads data this alone would be a major performance increase on a BTRFS Raid level (like ZFS RAIDZ). Side note this may sound crazy but the more I read about SSD's the less I wish to use/rely on them and RAM SSD's are crazly priced imo. =) Regards, Quenten -----Original Message----- From: ceph-devel-ow...@vger.kernel.org [mailto:ceph-devel-ow...@vger.kernel.org] On Behalf Of Slawomir Skowron Sent: Tuesday, 22 May 2012 3:52 PM To: Quenten Grasso Cc: Gregory Farnum; ceph-devel@vger.kernel.org Subject: Re: Designing a cluster guide I have some performance from rbd cluster near 320MB/s on VM from 3 node cluster, but with 10GE, and with 26 2.5" SAS drives used on every machine it's not everything that can be. Every osd drive is raid0 with one drive via battery cached nvram in hardware raid ctrl. Every osd take much ram for caching. That's why i'am thinking about to change 2 drives for SSD in raid1 with hpa tuned for increase durability of drive for journaling - but if this will work ;) With newest drives can theoreticaly get 500MB/s with a long queue depth. This means that i can in theory improve bandwith score, and take lower latency, and better handling of multiple IO writes, from many hosts. Reads are cached in ram from OSD daemon, VFS in kernel, nvram in ctrl, and in near future improve from cache in kvm (i need to test that - this will improve performance) But if SSD drive goes slower, it can get whole performance down in writes. It's is very delicate. Pozdrawiam iSS Dnia 22 maj 2012 o godz. 02:47 Quenten Grasso <qgra...@onq.com.au> napisał(a): > I Should have added For storage I'm considering something like Enterprise > nearline SAS 3TB disks running individual disks not raided with rep level of > 2 as suggested :) > > > Regards, > Quenten > > > -----Original Message----- > From: ceph-devel-ow...@vger.kernel.org > [mailto:ceph-devel-ow...@vger.kernel.org] On Behalf Of Quenten Grasso > Sent: Tuesday, 22 May 2012 10:43 AM > To: 'Gregory Farnum' > Cc: ceph-devel@vger.kernel.org > Subject: RE: Designing a cluster guide > > Hi Greg, > > I'm only talking about journal disks not storage. :) > > > > Regards, > Quenten > > > -----Original Message----- > From: ceph-devel-ow...@vger.kernel.org > [mailto:ceph-devel-ow...@vger.kernel.org] On Behalf Of Gregory Farnum > Sent: Tuesday, 22 May 2012 10:30 AM > To: Quenten Grasso > Cc: ceph-devel@vger.kernel.org > Subject: Re: Designing a cluster guide > > On Mon, May 21, 2012 at 4:52 PM, Quenten Grasso <qgra...@onq.com.au> wrote: >> Hi All, >> >> >> I've been thinking about this issue myself past few days, and an idea I've >> come up with is running 16 x 2.5" 15K 72/146GB Disks, >> in raid 10 inside a 2U Server with JBOD's attached to the server for actual >> storage. >> >> Can someone help clarify this one, >> >> Once the data is written to the (journal disk) and then read from the >> (journal disk) then written to the (storage disk) once this is complete this >> is considered a successful write by the client? >> Or >> Once the data is written to the (journal disk) is this considered successful >> by the client? > This one — the write is considered "safe" once it is on-disk on all > OSDs currently responsible for hosting the object. > > Every time anybody mentions RAID10 I have to remind them of the > storage amplification that entails, though. Are you sure you want that > on top of (well, underneath, really) Ceph's own replication? > >> Or >> Once the data is written to the (journal disk) and written to the (storage >> disk) at the same time, once complete this is considered a successful write >> by the client? (if this is the case SSD's may not be so useful) >> >> >> Pros >> Quite fast Write throughput to the journal disks, >> No write wareout of SSD's >> RAID 10 with 1GB Cache Controller also helps improve things (if really keen >> you could use a cachecade as well) >> >> >> Cons >> Not as fast as SSD's >> More rackspace required per server. >> >> >> Regards, >> Quenten >> >> -----Original Message----- >> From: ceph-devel-ow...@vger.kernel.org >> [mailto:ceph-devel-ow...@vger.kernel.org] On Behalf Of Slawomir Skowron >> Sent: Tuesday, 22 May 2012 7:22 AM >> To: ceph-devel@vger.kernel.org >> Cc: Tomasz Paszkowski >> Subject: Re: Designing a cluster guide >> >> Maybe good for journal will be two cheap MLC Intel drives on Sandforce >> (320/520), 120GB or 240GB, and HPA changed to 20-30GB only for >> separate journaling partitions with hardware RAID1. >> >> I like to test setup like this, but maybe someone have any real life info ?? >> >> On Mon, May 21, 2012 at 5:07 PM, Tomasz Paszkowski <ss7...@gmail.com> wrote: >>> Another great thing that should be mentioned is: >>> https://github.com/facebook/flashcache/. It gives really huge >>> performance improvements for reads/writes (especialy on FunsionIO >>> drives) event without using librbd caching :-) >>> >>> >>> >>> On Sat, May 19, 2012 at 6:15 PM, Alexandre DERUMIER <aderum...@odiso.com> >>> wrote: >>>> Hi, >>>> >>>> For your journal , if you have money, you can use >>>> >>>> stec zeusram ssd drive. (around 2000€ /8GB / 100000 iops read/write with >>>> 4k block). >>>> I'm using them with zfs san, they rocks for journal. >>>> http://www.stec-inc.com/product/zeusram.php >>>> >>>> another interessesting product is ddrdrive >>>> http://www.ddrdrive.com/ >>>> >>>> ----- Mail original ----- >>>> >>>> De: "Stefan Priebe" <s.pri...@profihost.ag> >>>> À: "Gregory Farnum" <g...@inktank.com> >>>> Cc: ceph-devel@vger.kernel.org >>>> Envoyé: Samedi 19 Mai 2012 10:37:01 >>>> Objet: Re: Designing a cluster guide >>>> >>>> Hi Greg, >>>> >>>> Am 17.05.2012 23:27, schrieb Gregory Farnum: >>>>>> It mentions for example "Fast CPU" for the mds system. What does fast >>>>>> mean? Just the speed of one core? Or is ceph designed to use multi core? >>>>>> Is multi core or more speed important? >>>>> Right now, it's primarily the speed of a single core. The MDS is >>>>> highly threaded but doing most things requires grabbing a big lock. >>>>> How fast is a qualitative rather than quantitative assessment at this >>>>> point, though. >>>> So would you recommand a fast (more ghz) Core i3 instead of a single >>>> xeon for this system? (price per ghz is better). >>>> >>>>> It depends on what your nodes look like, and what sort of cluster >>>>> you're running. The monitors are pretty lightweight, but they will add >>>>> *some* load. More important is their disk access patterns — they have >>>>> to do a lot of syncs. So if they're sharing a machine with some other >>>>> daemon you want them to have an independent disk and to be running a >>>>> new kernel&glibc so that they can use syncfs rather than sync. (The >>>>> only distribution I know for sure does this is Ubuntu 12.04.) >>>> Which kernel and which glibc version supports this? I have searched >>>> google but haven't found an exact version. We're using debian lenny >>>> squeeze with a custom kernel. >>>> >>>>>> Regarding the OSDs is it fine to use an SSD Raid 1 for the journal and >>>>>> perhaps 22x SATA Disks in a Raid 10 for the FS or is this quite absurd >>>>>> and you should go for 22x SSD Disks in a Raid 6? >>>>> You'll need to do your own failure calculations on this one, I'm >>>>> afraid. Just take note that you'll presumably be limited to the speed >>>>> of your journaling device here. >>>> Yeah that's why i wanted to use a Raid 1 of SSDs for the journaling. Or >>>> is this still too slow? Another idea was to use only a ramdisk for the >>>> journal and backup the files while shutting down to disk and restore >>>> them after boot. >>>> >>>>> Given that Ceph is going to be doing its own replication, though, I >>>>> wouldn't want to add in another whole layer of replication with raid10 >>>>> — do you really want to multiply your storage requirements by another >>>>> factor of two? >>>> OK correct bad idea. >>>> >>>>>> Is it more useful the use a Raid 6 HW Controller or the btrfs raid? >>>>> I would use the hardware controller over btrfs raid for now; it allows >>>>> more flexibility in eg switching to xfs. :) >>>> OK but overall you would recommand running one osd per disk right? So >>>> instead of using a Raid 6 with for example 10 disks you would run 6 osds >>>> on this machine? >>>> >>>>>> Use single socket Xeon for the OSDs or Dual Socket? >>>>> Dual socket servers will be overkill given the setup you're >>>>> describing. Our WAG rule of thumb is 1GHz of modern CPU per OSD >>>>> daemon. You might consider it if you decided you wanted to do an OSD >>>>> per disk instead (that's a more common configuration, but it requires >>>>> more CPU and RAM per disk and we don't know yet which is the better >>>>> choice). >>>> Is there also a rule of thumb for the memory? >>>> >>>> My biggest problem with ceph right now is the awful slow speed while >>>> doing random reads and writes. >>>> >>>> Sequential read and writes are at 200Mb/s (that's pretty good for bonded >>>> dual Gbit/s). But random reads and write are only at 0,8 - 1,5 Mb/s >>>> which is def. too slow. >>>> >>>> Stefan >>>> -- >>>> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in >>>> the body of a message to majord...@vger.kernel.org >>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>>> >>>> >>>> >>>> -- >>>> >>>> -- >>>> >>>> >>>> >>>> >>>> Alexandre D erumier >>>> Ingénieur Système >>>> Fixe : 03 20 68 88 90 >>>> Fax : 03 20 68 90 81 >>>> 45 Bvd du Général Leclerc 59100 Roubaix - France >>>> 12 rue Marivaux 75002 Paris - France >>>> >>>> -- >>>> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in >>>> the body of a message to majord...@vger.kernel.org >>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> >>> >>> >>> -- >>> Tomasz Paszkowski >>> SS7, Asterisk, SAN, Datacenter, Cloud Computing >>> +48500166299 >>> -- >>> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in >>> the body of a message to majord...@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >> >> >> >> -- >> ----- >> Pozdrawiam >> >> Sławek "sZiBis" Skowron >> -- >> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in >> the body of a message to majord...@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > N�����r��y���b�X��ǧv�^�){.n�+���z�]z���{ay� ʇڙ�,j > ��f���h���z� �w��� > ���j:+v���w�j�m���� > ����zZ+�����ݢj"��!�i > N�����r��y���b�X��ǧv�^�){.n�+���z�]z�{ay� ʇڙ�,j ��f���h���z� �w��� ���j:+v���w�j�m���� ����zZ+��ݢj"��!�i -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
