Hi Christian, Am 09.07.15 um 09:36 schrieb Christian Balzer: > > Hello, > > On Thu, 09 Jul 2015 08:57:27 +0200 Götz Reinicke - IT Koordinator wrote: > >> Hi again, >> >> time is passing, so is my budget :-/ and I have to recheck the options >> for a "starter" cluster. An expansion next year for may be an openstack >> installation or more performance if the demands rise is possible. The >> "starter" could always be used as test or slow dark archive. >> >> At the beginning I was at 16SATA OSDs with 4 SSDs for journal per node, >> but now I'm looking for 12 SATA OSDs without SSD journal. Less >> performance, less capacity I know. But thats ok! >> > Leave the space to upgrade these nodes with SSDs in the future. > If your cluster grows large enough (more than 20 nodes) even a single > P3700 might do the trick and will need only a PCIe slot. If I get you right, the 12Disk is not a bad idea, if there would be the need of SSD Journal I can add the PCIe P3700. In the 12 OSD Setup I should get 2 P3700 one per 6 OSDs. God or bad idea? > >> There should be 6 may be with the 12 OSDs 8 Nodes with a repl. of 2. >> > Danger, Will Robinson. > This is essentially a RAID5 and you're plain asking for a double disk > failure to happen. May be I do not understand that. size = 2 I think is more sort of raid1 ... ? And why am I asking for for a double disk failure? To less nodes, OSDs or because of the size = 2. > > See this recent thread: > "calculating maximum number of disk and node failure that can be handled > by cluster with out data loss" > for some discussion and python script which you will need to modify for > 2 disk replication. > > With a RAID5 failure calculator you're at 1 data loss event per 3.5 > years... > Thanks for that thread, but I dont get the point out of it for me. I see that calculating the reliability is some sort of complex math ... >> The workload I expect is more writes of may be some GB of Office files >> per day and some TB of larger video Files from a few users per week. >> >> At the end of this year we calculate to have +- 60 to 80 TB of lager >> videofiles in that cluster, which are accessed from time to time. >> >> Any suggestion on the drop of ssd journals? >> > You will miss them when the cluster does write, be it from clients or when > re-balancing a lost OSD. I can imagine, that I might miss the SSD Journal, but if I can add the P3700 later I feel comfy with it for now. Budget and evaluation related. Thanks for your helpful input and feedback. /Götz -- Götz Reinicke IT-Koordinator Tel. +49 7141 969 82420 E-Mail goetz.reinicke@xxxxxxxxxxxxxxx Filmakademie Baden-Württemberg GmbH Akademiehof 10 71638 Ludwigsburg www.filmakademie.de Eintragung Amtsgericht Stuttgart HRB 205016 Vorsitzender des Aufsichtsrats: Jürgen Walter MdL Staatssekretär im Ministerium für Wissenschaft, Forschung und Kunst Baden-Württemberg Geschäftsführer: Prof. Thomas Schadt
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