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===========System Design===========

Server A --> 2 PCI LSI HBA Cards

Server B --> 2 PCI LSI HBA Cards

8 x SAS Disk Shelf --> Dual SAS Controller 12 Slot Disk Shelf

96 Disks all SAS Seagate Enterprise Drives

Systems are cabled in redundant fashion through both HBA Cards and both Server A and B can see all of the disks in the shelf 2 times in "lsblk" (dual port)

Systems are running identical CentOS 7 (soon to be 8)

Server A handles 48 disks and has a file system on it, well call this file system FS-A. Server B handles 48 disks and has a file system on it, well call this file system FS-B.

This is setup this way to provide a high availability solution in the event Server A or Server B hardware fails the other can mount its file system and present it.

===========Question===========

Assuming Server A is handling FS-A and Sever B is handling FS-B are we able to utilize multipath connections to the drives on the respective servers holding the file system? I am concerned the second port of the drive is already consumed by the presence on the alternate server.

user7749674
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  • No sure I understand correctly but if you want HA for a cluster like setup, you must have all disks being part of a "shared storage" to be visible to both nodes. Though one node could use SCSI reservation to become "owner" of SCSI LUNs. If box A fails, other node could "reset" SCSI reservation of the failed node and acquire it for itself. For example standard Linux cluster suite (pacemaker and OCF agents) would handle it. – Jiri B Mar 27 '21 at 08:03
  • @JiriB The disks are visible to both nodes and while this is part of an HA setup the question is more can multipath be used (where the FS is mounted) while there is another host on the SAS bus that sees the drive. – user7749674 Mar 27 '21 at 18:42
  • I have only experience with an iSCSI cluster and while a filesystem which uses share block device is mounted on one node, the block device is still visible on other node, although it's reserved to active node. See https://www.systutorials.com/docs/linux/man/8-sg_persist/ But I'm not sure I understood what you wrote about multipath and disks' ports and HBA, I have never seen any SCSI disk shelf. Only iSCSI or FC. – Jiri B Mar 27 '21 at 19:18
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    @JiriB I have a pretty decent amount of experience with iSCSI and this definitely isn't the same thing. SAS disks have 2 ports vs SATA disks have 1 port hence why SAS disks can be used in HA type setups. My question is very specific on Dual Port SAS disk behavior. – user7749674 Mar 27 '21 at 22:55
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    @user7749674 did you ever figure this out. I have basically the same setup but single host (still two lsi hba). I installed multipath-tools but device mapper does not detect the drives for multipath. There are 168 raw block device nodes and I need to get to 84 mapped devices. I don't see seagate in the default config as a vendor. Is there a vendor entry that needs to be added? – David Cowden Nov 11 '21 at 08:00

0 Answers0