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Disk staging unit

_5
Level 3
Partner
Hello Netbackup guru's

I have a doubt about the creating the disk staging unit 

I got 5TB disk ( which is my D drive ) . Is it recommended or possible  to create the multiple disk storage unit pointing the same drive     (directly pointing the D drive-absolute path for storage  )-All the disk storage units i am planning to use for the basic staging purpose 

Thank in Advance .

7 REPLIES 7

bak
Level 4
You cannot point two storage units at the same exact location, but you could point multiple storage units at different directories on the same disk.

For example, this would not work:
STU1 -> D:\Disk1
STU2 -> D:\Disk1

But this would work:
STU1 -> D:\Disk1
STU2 -> D:\Disk2

Nicolai
Moderator
Moderator
Partner    VIP   


I not always a good  idea to create multiple disk storage unit on the same disk spindles as this would lead to disk trashing (disk seek forth and back).

Test it out and with a disk performance program and find out what best for you.

PS: Test concurrent read and write - eg. STU1 does read STU2 does write.


Anton_Panyushki
Level 6
Certified

I think you should split your 5Tb LUN into, say, 5 1Tb ones and then create a separate DSSU against each LUN. Next, as you got your brand-new DSSUs, you should create a storage unit group and add these DSSUs into that storage unit group. Symantec recommends "round-robbin" priority for that sort of storage unit groups. Finally, you configure backup policies with storage unit group as a backup destination and voila you have fault-tolerant D2D2T solution. It is should be mentioned that the best practice is to spread multiple DSSUs across a numberof  media servers to prevent media server failure.

Ed_Wilts
Level 6

Do NOT mix multiple staging storage units on the same drive.  Here's why...

When you're backing to say dssu1, you will likely eventually hit the highwater mark.  At this point, NetBackup will attempt to clean up space by deleting the staged images, but it will ONLY look at dssu1.  It will not look at dssu2 even though it is on the same volume.  So let's say you have a highwater mark at 80% (4TB).  You have 3.5TB in dssu2 and 200GB in dssu1 and it's all been destaged already.  You start a backup job that will require 1TB for dssu1.  There is no way to complete this job because NetBackup doesn't have enough space and won't clean it up in dssu1.

There is a technote on this as well but the short answer is do not do this.

Will_Restore
Level 6
disk thrashing might ultimately trash your disk but it would take a while devil

Will_Restore
Level 6
we plan to do this in new environment

Nicolai
Moderator
Moderator
Partner    VIP   

Creating more disk storage unit's pointing to the same LUN  won't make the disk faster. I would go for one big 5TB disk storage unit.