Using a SAS tape drive on the external ports of a RAID adapter

[perdrix]

I've heard suggestions that this is a "no-no". Is this because of performance issues - if so I don't have any problem as this is a very lightly used RAID array.

I just want to attach a SAS tape drive to do backups of the array, and don't really want to add a extra SAS HBA just for the tape drive (as that would mean replacing the Mobo).

D.

 

[Spartacus]

Its not necessarily a no-no because of performance issues, but most enterprise use cases have a raid controller setup in.. well raid so its not really compatible. I don't see this being an issue if the controller is set in HBA/IT-mode.

Just make sure whatever card you have has sufficient bandwidth to both serve and be served the data to backup to the tapes (perhaps reduce the number of jobs you run simultaneously if you have an older card)

 

[perdrix]

Maybe I wasn't clear the adapter (ASR51245) is definitely hosting an 8 drive RAID5 array on its internal ports.

 

[Spartacus]

Ah I would defiinitely recommend getting a cheap stand alone LSI model then.
Do you just not have enough pcie ports or why would you have to get another motherboard?

 

[perdrix]

That's indeed the issue no more PCI/e slots

 

[Spartacus]

what motherboard and/or other pcie cards do you have?

 

[UhClem]

Maybe I wasn't clear the adapter (ASR51245) is definitely hosting an 8 drive RAID5 array on its internal ports.

Adaptec says the 51245 supports SAS (&Sata) tape drives (link).
If the 5 series allows for configuring a mix of RAIDed & non-RAIDed drives, like most Adaptec (RAID) controllers, you should just try it.

 

[Jason Antes]

The biggest issue with tape drives (assuming LTO here) is keeping them fed to reduce shoe shining. If you can't keep it's buffer full the drive will stop, wait for the buffer, rewind a bit, then start writing until the buffer is empty, and then repeat. That sort of thing decreases the life of the drive and the tapes. If you can keep it fed it will run and last a long time. Starting at LOT5, it can write natively at 140MBps, LTO6 - 160MBps, LTO7 - 300MBps, and LTO8 - 360MBps. If you go compressed, then those numbers go up to 280, 400, 750, and 750MBps.

 

[UhClem]

If "shoeshine" is an issue, you can do a "pushbroom" [on a long hallway] with (e.g.)

 backup-program | dd bs=8G iflag=fullblock oflag=direct of=/dev/TapeName

(change the "8G" to "RAM/2"; as typical, backups are done in the off-hours)