Hi, thanks for the explanation, but... Twisting the Ceph storage model as you plan it is not a good idea : - You will decrease the support level(I'm not sure many people will build such an architecture) - You are certainly going to face strange issues with HW Raid on top of Ceph OSD - You should'nt want to go to size=2. I know the counterparts of size=3 (IOPS, Usable space), but it seems not really safe to downgrade to size=2. - Your servers seem to have enough horsepower regarding CPU,RAM and disks. But you havent't told us about Ceph replication Network. At least 10Gbe, i hope. - Your public network should be more than 1Gbe too, far more.. - How will you export VM ? single KVM samba server ? Ceph authx clients ??? - Rapidly, with size=3, you have, with 4 servers : 4*8*2/3=22TB usable space. With 100 VDI, 220 GB per VM.. Is it enough to expand those VM sizes ? In a conclusion,i fully understand the issues doing a complete test lab before buying a complete cluster. But, you should do a few tests before to tweak the solution to your needs. Good luck Best regards Le 14/11/2017 à 11:36, Oscar Segarra a écrit : > Hi Anthony, > > > o I think you might have some misunderstandings about how Ceph works. > Ceph is best deployed as a single cluster spanning multiple servers, > generally at least 3. Is that your plan? > > I want to deply servers for 100VDI Windows 10 each (at least 3 servers). > I plan to sell servers dependingo of the number of VDI required by my > customer. For 100 VDI --> 3 servers, for 400 VDI --> 4 servers > > This is my proposal of configuration: > > *Server1:* > CPU: 2x16 Core > RAM: 512 > Disk: 2x400 for OS and 8x1.9TB for VM (SSD) > > *Server2:* > CPU: 2x16 Core > RAM: 512 > Disk: 2x400 for OS and 8x1.9TB for VM (SSD) > > *Server3:* > CPU: 2x16 Core > RAM: 512 > Disk: 2x400 for OS and 8x1.9TB for VM (SSD) > > *Server4:* > CPU: 2x16 Core > RAM: 512 > Disk: 2x400 for OS and 8x1.9TB for VM (SSD) > ... > *ServerN:* > CPU: 2x16 Core > RAM: 512 > Disk: 2x400 for OS and 8x1.9TB for VM (SSD) > > If I create an OSD for each disk and I pin a core for each osd in a > server I wil need 8 cores just for managing osd. If I create 4 RAID0 of > 2 disks each, I will need just 4 osd, and so on: > > 1 osd x 1 disk of 4TB > 1 osd x 2 disks of 2TB > 1 odd x 4 disks of 1 TB > > If the CPU cycles used by Ceph are a problem, your architecture has IMHO > bigger problems. You need to design for a safety margin of RAM and CPU > to accommodate spikes in usage, both by Ceph and by your desktops. > There is no way each of the systems you describe is going to have enough > cycles for 100 desktops concurrently active. You'd be allocating each > of them only ~3GB of RAM -- I've not had to run MS Windows 10 but even > with page sharing that seems awfully tight on RAM. > > Sorry, I think my design has not been correctly explained. I hope my > previous explanation clarifies it. The problem is i'm in the design > phase and I don't know if ceph CPU cycles can be a problem and that is > the principal object of this post. > > With the numbers you mention throughout the thread, it would seem as > though you would end up with potentially as little as 80GB of usable > space per virtual desktop - will that meet your needs? > > Sorry, I think 80GB is enough, nevertheless, I plan to use RBD clones > and therefore even with size=2, I think I will have more than 80GB > available for each vdi. > > In this design phase where I am, every advice is really welcome! > > Thanks a lot > > 2017-11-13 23:40 GMT+01:00 Anthony D'Atri <aad@xxxxxxxxxxxxxx > <mailto:aad@xxxxxxxxxxxxxx>>: > > Oscar, a few thoughts: > > o I think you might have some misunderstandings about how Ceph > works. Ceph is best deployed as a single cluster spanning multiple > servers, generally at least 3. Is that your plan? It sort of > sounds as though you're thinking of Ceph managing only the drives > local to each of your converged VDI hosts, like local RAID would. > Ceph doesn't work that way. Well, technically it could but wouldn't > be a great architecture. You would want to have at least 3 servers, > with all of the Ceph OSDs in a single cluster. > > o Re RAID0: > > > Then, may I understand that your advice is a RAID0 for each 4TB? For a > > balanced configuration... > > > > 1 osd x 1 disk of 4TB > > 1 osd x 2 disks of 2TB > > 1 odd x 4 disks of 1 TB > > > For performance a greater number of smaller drives is generally > going to be best. VDI desktops are going to be fairly > latency-sensitive and you'd really do best with SSDs. All those > desktops thrashing a small number of HDDs is not going to deliver > tolerable performance. > > Don't use RAID at all for the OSDs. Even if you get hardware RAID > HBAs, configure JBOD/passthrough mode so that OSDs are deployed > directly on the drives. This will minimize latency as well as > manifold hassles that one adds when wrapping drives in HBA RAID volumes. > > o Re CPU: > > > The other question is considering having one OSDs vs 8 OSDs... 8 OSDs will > > consume more CPU than 1 OSD (RAID5) ? > > > > As I want to share compute and osd in the same box, resources consumed by > > OSD can be a handicap. > > > If the CPU cycles used by Ceph are a problem, your architecture has > IMHO bigger problems. You need to design for a safety margin of RAM > and CPU to accommodate spikes in usage, both by Ceph and by your > desktops. There is no way each of the systems you describe is going > to have enough cycles for 100 desktops concurrently active. You'd > be allocating each of them only ~3GB of RAM -- I've not had to run > MS Windows 10 but even with page sharing that seems awfully tight on > RAM. > > Since you mention PProLiant and 8 drives I'm going assume you're > targeting the DL360? I suggest if possible considering the 10SFF > models to get you more drive bays, ditching the optical drive. If > you can get rear bays to use to boot the OS from, that's better yet > so you free up front panel drive bays for OSD use. You want to > maximize the number of drive bays available for OSD use, and if at > all possible you want to avoid deploying the operating system's > filesystems and OSDs on the same drives. > > With the numbers you mention throughout the thread, it would seem as > though you would end up with potentially as little as 80GB of usable > space per virtual desktop - will that meet your needs? One of the > difficulties with converged architectures is that storage and > compute don't necessarily scale at the same rate. To that end I > suggest considering 2U 25-drive-bay systems so that you have room to > add more drives. > > > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx <mailto:ceph-users@xxxxxxxxxxxxxx> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > <http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com> > > > > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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