Log In

Come Join Us!

Are you a
Computer / IT professional?
Join Tek-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Tek-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Streams and readers - best practise with multiple drives?

Streams and readers - best practise with multiple drives?

Streams and readers - best practise with multiple drives?

I have a large file server with a SAS attached library with two LTO3 drives (Dell TL4000).

So, my main storage policy is set to use 2 streams with multiplexing of 4.

My File System iDataAgents are set to use between 4 and 8 data readers based on what I've (fairly crudely) determined to yield the most throughput.

The clients vary between a couple hundred gig and three tb or so.

What I'm seeing is that often a backup job for a large server will start with all 8 available data readers in use (4 to each physical LTO drive so the backup job is writing to both drives) and as the job continues and readers complete, the total reader count reduces, until, say only 1 reader is in use on each drive.

At this point other jobs will start and will take the number of readers per drive up to 4 again.

The problem/issue is that I seem to only be able to get 4 readers to each drive, and those readers can't saturate the drive.

Is there any way with the available drives to simply get more throughput to the drive?

I know the drives will each do 60-70mb/sec if fed from quick enough spindles, and the chunk size is 256kb which seems to yield best results, but I think the issue is more to do with the types of files (total mix of sizes and quantities) and the limits of what each individual reader will pull off disk vs. what the physical disk subsystem can provide.

Bit of a ramble there but fingers crossed it makes sense!

RE: Streams and readers - best practise with multiple drives?

If you enhance the Multiplexing factor, more readers will be able to use the tape drive. The number of readers is dependent on the number of physical drives of the server or the option Allow multiple data readers within a drive or mount point (SubClient). In CommVault Books Online it states: "Note that the actual number of streams shown will vary as the job progresses." That may explain (??) the reduction of the total reader count as the job continues.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Tek-Tips Forums free from inappropriate posts.
The Tek-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Tek-Tips forums is a member-only feature.

Click Here to join Tek-Tips and talk with other members!

Close Box

Join Tek-Tips® Today!

Join your peers on the Internet's largest technical computer professional community.
It's easy to join and it's free.

Here's Why Members Love Tek-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close