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Are these nodes connected to a dedicated or a shared (in the sense there
are other workloads running) network switches? How fast (1G, 10G or faster)
are the interfaces? Also, how much RAM are you using? There's a rule of
thumb that says you should dedicate at least 1GB of RAM for each 1 TB of
raw disk space. How the clients are consuming the storage? Are they virtual
machines? Are you using iSCSI to connect those? Are these clients the same
ones you're testing against your regular SAN storage and are they
positioned in a similar fashion (ie: over a steady network channel)? What
Ceph version are you using?

Finally, replicas are normally faster than erasure coding, so you're good
on this. It's *never* a good idea to enable RAID cache, even when it
apparently improves IOPS (the magic of Ceph relies on the cluster, it's
network and the number of nodes, don't approach the nodes as if they where
isolate storage servers). Also, RAID0 should only be used as a last resort
for the cases the disk controller doesn't offer JBOD mode.

[]'s
Hubner

On Fri, Feb 17, 2017 at 7:19 AM, Vahric Muhtaryan <vahric at doruk.net.tr>
wrote:

> Hello All ,
>
> First thanks for your answers . Looks like everybody is ceph lover :)
>
> I believe that you already made some tests and have some results because
> of until now we used traditional storages like IBM V7000 or XIV or Netapp
> or something we are very happy to get good iops and also provide same
> performance to all instances until now.
>
> We saw that each OSD eating a lot of cpu and when multiple client try to
> get same performance from ceph its looks like not possible , ceph is
> sharing all things with clients and we can not reach hardware raw iops
> capacity with ceph. For example each SSD can do 90K iops we have three on
> each node and have 6 nodes means we should get better results then what we
> have now !
>
> Could you pls share your hardware configs , iops test and advise our
> expectations correct or not ?
>
> We are using Kraken , almost all debug options are set 0/0 , we modified
> op_Tracker or some other ops based configs too !
>
> Our Hardware
>
> 6 x Node
> Each Node Have :
> 2 Socket Intel(R) Xeon(R) CPU E5-2630L v3 @ 1.80GHz each and total 16
> core and HT enabled
> 3 SSD + 12 HDD (SSDs are in journal mode 4 HDD to each SSD)
> Each disk configured Raid 0 (We did not see any performance different with
> JBOD mode of raid card because of that continued with raid 0 )
> Also raid card write back cache is used because its adding extra IOPS too
> !
>
> Our Test
>
> Its %100 random and write
> Ceph pool is configured 3 replica set. (we did not use 2 because at the
> failover time all system stacked and we couldn’t imagine great tunning
> about it because some of reading said that under high load OSDs can be down
> and up again we should care about this too ! )
>
> Test Command : fio --randrepeat=1 --ioengine=libaio --direct=1
> --gtod_reduce=1 --name=test --filename=test --bs=4k —iodepth=256 --size=1G
> --numjobs=8 --readwrite=randwrite —group_reporting
>
> Achieved IOPS : 35 K (Single Client)
> We tested up to 10 Clients which ceph fairly share this usage like almost
> 4K for each
>
> Thanks
> Regards
> Vahric Muhtaryan
>
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