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tpellegrini

6 Posts

1261

January 25th, 2022 13:00

Multiple SAS Tape Drives Connected to One Host

Please forgive these basic questions. I did search the online documentation and these forums but did not find the answers.

I have a PowerVault TL4000 with two SAS LTO6 drives installed. I have only ever used 1 drive connected to one host but would like to change this to use both drives, still connected only to one host. I'm seeking guidance/clarification on the proper cabling to accomplish this.

Do I use two separate cables from two separate channels from the host, or can I use one host cable connection to one drive daisy-chained to the other drive? Alternatively, I have seen Y-cables for some SAS bus cards that would seem to offer one host port connection to both drives. I cannot seem to find a Mini-SAS HD (SFF-8644) Y cable however, which is the connector the new host came with. 

Also, please help me verify that my expectation is correct that having the two drives connected will allow the device to write data to two tapes simultaneously? Is the failover upgrade key required for this? If I do not have this key will it work and/or is there any benefit?

Thanks in advance.

 

~ Tony

DiegoLopez

4 Operator

 • 

2.7K Posts

January 26th, 2022 08:00

Hello @tpellegrini,


What interface are you currently using? And what about the host? What card do you have on the host?


SAS cabled devices do not support Daisy Chaining.


You can check the Dell PowerVault TL2000 Tape Library and TL4000 Tape
Library User's Guide here: https://dell.to/344vvnj


Regards.

tpellegrini

6 Posts

January 31st, 2022 07:00

Thanks for your reply. If daisy-chaining is not supported that has to mean that independent connections to the host are required, which was the answer I was seeking.

Origin3k

4 Operator

 • 

2.4K Posts

January 31st, 2022 10:00

To give a better answer..

yes you need 2 long SAS cables and wire them up to one host(1 dual port HBA is fine).  There is no Y-cable for that purpose. You need the Y-cable when using the iSCSI Bridge (optional peace of hardware) which is available for the TL4000/2000 to convert the SAS solution into a 2x1GbE iSCSI one.

But back to SAS. After installing the device drivers (some backup application comes with own set of drivers!) it depends on a additional setting if your OS/App see one of the following

  1. One tape library(changer) with two LTO drive and 48 slots
    or
  2. Two tape libraries(changers) with one LTO drive and 24 Slots each

How to configure it? Go back to the TL4000 and and specify the number of logical partitions. You can create multiple libraries if you want or have a need for.

For what? Our CA Backup Arcserve require a additional license if you want to use more than one drive within a single library which costs some extra $$$$ which we have avoided by splitting the phys. library into 2.
Speaking of CA ArcServe you have to configure the "Tape" by selecting the right library together with the right drive. Its not in the way that you have to pick up the library and your done.

We run jobs in parallel and every one use a different tape library/partition). On another setup we use the partition feature to hook up the library to different pyhs. Backup servers which use different backup apps. (ArcServe and Veeam)

It have nothing to do with the Failover Key.

Regards,
Joerg

tpellegrini

6 Posts

February 1st, 2022 07:00

Thanks so much for the clarification. I appreciate you taking the time to provide this guidance.

My interest in this was essentially casual. (That is, I have two drives, one's unused, can I use it?) Armed now with a better understanding of how this works, it seems unlikely I will pursue it further.

Thanks again!

 

~ Tony

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