Hi Satish, that really completely depends on your controller. For what it's worth: We have AVAGO MegaRAID controllers (9361 series). They can be switched to a "JBOD personality". After doing so and reinitializing (poewrcycling), the cards change PCI-ID and run a different firmware, optimized for JBOD mode (with different caching etc.). Also, the block devices are ordered differently. In that mode, new disks will be exported as JBOD by default, but you can still do RAID1 and RAID0. I think RAID5 and RAID6 are disabled, though. We are using those to have a RAID 1 for our OS and export the rest as JBOD for CephFS. So there surely are controllers which can only do JBOD in addition (without a special controller mode / "personality"), controllers which can be switched, but simple RAID levels are still possible, and I'm also sure there are controllers out there which can be switched to JBOD mode and can't do anything RAID anymore in that mode. If that's the case, just go with software RAID for the OS, or install your servers with a good deployment tool so you can just reinstall them if the OS breaks (we also do that for some Ceph servers with simpler RAID controllers). With a good deployment tool, reinstalling takes 1 click and waiting 40 minutes - but of course, the server will still be down until a broken OS HDD is replaced physically. But Ceph has redundancy for that :-). Cheers, Oliver Am 20.07.2018 um 23:52 schrieb Satish Patel: > Thanks Brian, > > That make sense because i was reading document and found you can > either choose RAID or JBOD > > On Fri, Jul 20, 2018 at 5:33 PM, Brian : <brians@xxxxxxxx> wrote: >> Hi Satish >> >> You should be able to choose different modes of operation for each >> port / disk. Most dell servers will let you do RAID and JBOD in >> parallel. >> >> If you can't do that and can only either turn RAID on or off then you >> can use SW RAID for your OS >> >> >> On Fri, Jul 20, 2018 at 9:01 PM, Satish Patel <satish.txt@xxxxxxxxx> wrote: >>> Folks, >>> >>> I never used JBOD mode before and now i am planning so i have stupid >>> question if i switch RAID controller to JBOD mode in that case how >>> does my OS disk will get mirror? >>> >>> Do i need to use software raid for OS disk when i use JBOD mode? >>> _______________________________________________ >>> 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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