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Tape drive multipathing in HP-UX 11iv3

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debjit-India
Frequent Advisor

Tape drive multipathing in HP-UX 11iv3

I have a server HP-UX 11iv3 and 4 HBA. the Library having 16 drives. 2 HBA has been given access to Library. when I am giving ioscan -fnCtape i can see 32 drives in CLAIMED mode. Is this is a supported configuration. Is that means that tape drives are multipath and charing the load.
8 REPLIES
Steven Clementi
Honored Contributor

Re: Tape drive multipathing in HP-UX 11iv3

Last I heard multipathing on Tape Libraries was "not" supported.

Even though theoretically possibly to have multipaths to a tape device, I don't think any backup software allows you to utilize it properly in that fashion. I could be slightly out of the loop on new developments. ;o)


Steven
Steven Clementi
HP Master ASE, Storage and Clustering
MCSE (NT 4.0, W2K, W2K3)
VCP (ESX2, Vi3, vSphere4, vSphere5)
RHCE
NPP3 (Nutanix Platform Professional)
debjit-India
Frequent Advisor

Re: Tape drive multipathing in HP-UX 11iv3

in Hp-UX 11iv2 it seems not supported. but in hp-ux 11iv3 if you give ioscan -m lun it only shows persistent dsf paths. but any way there are dual paths in the physical arena. I am confused.
Uwe Zessin
Honored Contributor
Solution

Re: Tape drive multipathing in HP-UX 11iv3

A disk is a random-access device and a read or write command can be retried easily. A tape is a sequential device. Commands cannot be retried that easily - some cannot at all.
.
debjit-India
Frequent Advisor

Re: Tape drive multipathing in HP-UX 11iv3

I can run backup on those tape drives that are two times showing in the ioscan output. that means it is working and multipath is supported.


if multipathing is not a supported configuration then the path will not come as a claimed and ioscan -m lun is showing only one path that means native multipathing (HP-UX 11iv3 multipthing product) supporting tape drive.

tell me if I am wronmg here.

# ioscan -kfnCtape|grep 4-SCSI
tape 9 0/0/6/1/1.11.23.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 17 0/0/6/1/1.11.24.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 10 0/0/6/1/1.11.25.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 16 0/0/6/1/1.11.28.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 5 0/0/6/1/1.11.29.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 6 0/0/6/1/1.11.31.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 11 0/0/6/1/1.11.131.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 57 0/0/6/1/1.11.136.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 12 0/0/6/1/1.11.137.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 7 0/0/6/1/1.11.138.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 13 0/0/6/1/1.11.141.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 8 0/0/6/1/1.11.149.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 18 0/0/6/1/1.11.150.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 14 0/0/6/1/1.11.154.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 15 0/0/6/1/1.11.155.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 4 0/0/6/1/1.11.157.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 37 0/0/6/1/1.11.158.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 40 1/0/12/1/1.11.23.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 43 1/0/12/1/1.11.24.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 49 1/0/12/1/1.11.25.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 53 1/0/12/1/1.11.28.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 45 1/0/12/1/1.11.29.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 44 1/0/12/1/1.11.31.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 52 1/0/12/1/1.11.131.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 34 1/0/12/1/1.11.136.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 46 1/0/12/1/1.11.137.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 47 1/0/12/1/1.11.138.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 51 1/0/12/1/1.11.141.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 39 1/0/12/1/1.11.149.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 48 1/0/12/1/1.11.150.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 55 1/0/12/1/1.11.154.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 54 1/0/12/1/1.11.155.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 2 1/0/12/1/1.11.157.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI
tape 50 1/0/12/1/1.11.158.255.0.0.0 stape CLAIMED DEVICE HP Ultrium 4-SCSI


# ioscan -m lun|grep 4-SCSI
tape 19 64000/0xfa00/0x61 estape CLAIMED DEVICE online HP Ultrium 4-SCSI
tape 20 64000/0xfa00/0x62 estape CLAIMED DEVICE online HP Ultrium 4-SCSI
tape 21 64000/0xfa00/0x63 estape CLAIMED DEVICE online HP Ultrium 4-SCSI
tape 22 64000/0xfa00/0x64 estape CLAIMED DEVICE online HP Ultrium 4-SCSI
tape 23 64000/0xfa00/0x65 estape CLAIMED DEVICE online HP Ultrium 4-SCSI
tape 24 64000/0xfa00/0x66 estape CLAIMED DEVICE online HP Ultrium 4-SCSI
tape 25 64000/0xfa00/0x67 estape CLAIMED DEVICE online HP Ultrium 4-SCSI
tape 26 64000/0xfa00/0x68 estape CLAIMED DEVICE online HP Ultrium 4-SCSI
tape 27 64000/0xfa00/0x69 estape CLAIMED DEVICE online HP Ultrium 4-SCSI
tape 28 64000/0xfa00/0x6a estape CLAIMED DEVICE online HP Ultrium 4-SCSI
tape 29 64000/0xfa00/0x6b estape CLAIMED DEVICE online HP Ultrium 4-SCSI
tape 30 64000/0xfa00/0x6c estape CLAIMED DEVICE online HP Ultrium 4-SCSI
tape 31 64000/0xfa00/0x6d estape CLAIMED DEVICE online HP Ultrium 4-SCSI
tape 32 64000/0xfa00/0x6e estape CLAIMED DEVICE online HP Ultrium 4-SCSI
tape 33 64000/0xfa00/0x70 estape CLAIMED DEVICE online HP Ultrium 4-SCSI
tape 36 64000/0xfa00/0x21b estape CLAIMED DEVICE online HP Ultrium 4-SCSI
tape 56 64000/0xfa00/0x22f estape CLAIMED DEVICE online HP Ultrium 4-SCSI
Uwe Zessin
Honored Contributor

Re: Tape drive multipathing in HP-UX 11iv3

> that means it is working and multipath is supported.

It means it is working on one path at a time, but I doubt that you have tested a path failover. multipath is much more than testing if you can send a bit of data down a path at a time.

'supported' as described be Steven Clementi should be understood as a statement made by the vendor (e.g. HP) which indicates that:
1: he has done full tests, and
2: he is willing do deal with problem reports
.
debjit-India
Frequent Advisor

Re: Tape drive multipathing in HP-UX 11iv3

The "HP-UX 11i v3 Native Multi-Pathing for Mass Storage" whitepaper donot told anything strongly about multipathing but wrote the below things

Policies Supported for Tapes, Changer and Pass-Through Devices
Because of the serial nature of the I/O flow to tape and changer devices, only one path selection mechanism is supported by estape and eschgr drivers: path lock down (path_lockdown). When opening a tape or changer LUN DSF, the mass storage subsystem internally selects the optimal lunpath onto which all the I/O operations are sent.
Devices claimed by the pass-through driver (esctl) also use path lockdown as the I/O load balance policy.

that means no failover, but multipathing.

thanks all. assigning points to you all.
debjit-India
Frequent Advisor

Re: Tape drive multipathing in HP-UX 11iv3

It looks like native multipathing of HP-UX 11iv3 support multipathing of tape drives but failover cannot be possible
krusty
Honored Contributor

Re: Tape drive multipathing in HP-UX 11iv3

Debjit,

I agree with Uwe here. Just because you can see two paths to a device does not mean multipathing is supported. It just means you can see the device through two paths.

It sounds to me like the tape SAN design needs to be fixed, as when I set up a tape SAN I only allow one path to be visable to avoid seeing the tape drives more than once on a host. I would look into modifying your zoning as to avoid this confusion in the future.

Sincerely,

Curt
"In Vino Veritas"