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Share MSL2024 (SAS, LTO4) between two servers?

Neal Howard
Advisor

Share MSL2024 (SAS, LTO4) between two servers?

Is it possible to share an SAS-connected MSL2024 LTO4 library between two servers... simultaneously connected to both servers at the same time, and just using basic time scheduling to ensure that only one server is writing to or actually using the library at a time?

 

I know this kind of tape sharing & cabling strategy was both possible, and fairly commonplace with good old fashioned parallel SCSI technology, but I'm not having much luck even searching for information whether such a concept is even supported for SAS or not.

 

I did find one single reference to IBM branded SAS LTO5 tape drives which supposedly have some kind of limitation to their firmware that they cannot act as more than one "initiator" at a time, but I can find nothing about whether the HP MSL libraries (Overland-oem'ed?) or the particular LTO4 drive in my library (not sure who the drive's OEM is) are capable of being physically connected simultaneously to two different servers at once.

3 REPLIES
Torsten.
Acclaimed Contributor

Re: Share MSL2024 (SAS, LTO4) between two servers?

A MSL2024 (it's not overland! IMHO it is www.bdt-solutions.eu) can be shared or even partitioned into 2 logical libraries only if on fibre I think.

Depending on the software you are using you can connect the first drive to the first server (that will have robotics controll), the second drive to another server (that runs kind of media agent).

 

There are sas fan out cables, but only in one direction: 1 initiator to many targets.


Hope this helps!
Regards
Torsten.

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Neal Howard
Advisor

Re: Share MSL2024 (SAS, LTO4) between two servers?

The MSL2024 sure looks like an Overland NEO 200s to me... virutally identical except for color of paint, plastics and cosmetic appearances on the front panel. 

 

Anyway, I've got the SAS-connected version with only one single SAS connector on the back. No FC or classic SCSI. My servers are Linux  (RHEL5), and I'm using the simple command-line "mtx" program to operate the robotics and "tar" to backup files to tape. The server which has the library locally attached reports the tape drive and robotics as distinct and separate SAS devices on the HBA card.

 

My reson for wanting to share the library between two servers, is that I have two servers with a few terabytes of data on each, roughly similar in size and purpose to each other. I'm presently backing up the second server using remote tape  (rmt) via gnu tar over a dedicated gigabit network link to the tape drive in the first server and using remsh commands to tell mtx to operate the robotics over the network. The first server, with the library attached locally to its HBA card finishes its backup in a few hours, the second server..... going over the network via tar/remote tape/rmt is taking over 30 hours to back up the same volume of data  (about eight LTO4 cartidges for each server). I've tried every trick in the book using various buffer programs at each end to try to get the remote tape transfer to  go faster but nothing works, and I am nowhere near saturating my dedicated gigabit network link.

 

If there was some way to share the library between the two servers, it would solve my slow backup problem easily.  I'm wishing now that I would have not bought the SAS version of this library, but the legacy U320 parallel SCSI version instead, which would easily share between the two server machines.

Torsten.
Acclaimed Contributor

Re: Share MSL2024 (SAS, LTO4) between two servers?

Probably the only solution I can imagine is using a (third-party) sas-switch and 2 logical libraries (this will need 2 drives). If you have 2 drives, you can also connect each drive to a server, the "master" server has control over the robotics only.

 

FC drives can be shared easier, but you need a fc switch, because this library has always a single connector per drive only (a few have 2, but for redundancy only). 


Hope this helps!
Regards
Torsten.

__________________________________________________
There are only 10 types of people in the world -
those who understand binary, and those who don't.

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No support by private messages. Please ask the forum!

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