Agree with everything Robin wrote here. RAID HBAs FTL. Even in passthrough mode, it’s still an [absurdly expensive] point of failure, but a server in the rack is worth two on backorder.
Moreover, I’m told that it is possible to retrofit with cables and possibly an AIC mux / expander. e.g. https://www.ebay.com/itm/176400760681 Granted, I haven’t done this personally so I can’t speak to the BOM and procedure. For OSD nodes it probably isn’t worth the effort. Some of the LSI^H^H^H^HPERC HBAs — to my astonishment — don’t have a passthrough setting/mode. This document though implies that this SKU does. https://www.dell.com/support/manuals/en-ae/poweredge-r7525/perc11_ug/technical-specifications-of-perc-11-cards?guid=guid-aaaf8b59-903f-49c1-8832-f3997d125edf&lang=en-us You should be able to set individual drives to passthrough: storcli64 /call /eall /sall set jbod=on or depending on the SKU and storcli revision, for the whole HBA storcli64 /call set personality=JBOD racadm set Storage.Controller.1.RequestedControllerMode HBA or racadm set Storage.Controller.1.RequestedControllerMode EnhancedHBA then jobqueue create RAID.Integrated.1-1 server action power cycle LSI and Dell have not been particularly consistent with these beasts. — aad >> Hello, >> >> We would like to repurpose some Dell PowerEdge R750s for a Ceph cluster. >> >> Currently the servers have one H755N RAID controller for each 8 drives. (2 >> total) > The N variant of H755N specifically? So you have 16 NVME drives in each > server? > >> I have been asking their technical support what needs to happen in >> order for us to just rip out those raid controllers and cable the >> backplane directly to the motherboard/PCIe lanes and they haven't been >> super enthusiastic about helping me. I get it just buy another 50 >> servers, right? No big deal. > I don't think the motherboard has enough PCIe lanes to natively connect > all the drives: the RAID controller effectively functioned as a > expander, so you needed less PCIe lanes on the motherboard. > > As the quickest way forward: look for passthrough / single-disk / RAID0 > options, in that order, in the controller management tools (perccli etc). > > I haven't used the N variant at all, and since it's NVME presented as > SCSI/SAS, I don't want to trust the solution of reflashing the > controller for IT (passthrough) mode. > > -- > Robin Hugh Johnson > Gentoo Linux: Dev, Infra Lead, Foundation President & Treasurer > E-Mail : robb...@gentoo.org > GnuPG FP : 11ACBA4F 4778E3F6 E4EDF38E B27B944E 34884E85 > GnuPG FP : 7D0B3CEB E9B85B1F 825BCECF EE05E6F6 A48F6136 > _______________________________________________ > ceph-users mailing list -- ceph-users@ceph.io > To unsubscribe send an email to ceph-users-le...@ceph.io _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-le...@ceph.io
