DASH Synthetic Full - Streams?
Troy, John,
Thanks for the input.
Long story short I have a new MA to build and I have 24x2tb spindles so have choices to make about how many physical RAID sets to use.
My biggest client is an 8tb or so file server that we do each week using a DASH Synthetic Full. The content of it doesn't change much.
I'm looking for the best way to configure the maglib spindles on the new MA so that when I do the initial Aux Copy from the current MA to "seed" the new one the data is nicely spread out across all the spindles - that way when we do the weekly aux copy to tape, I'm not stuck reading most of my data from the same set of physical spindles (which defeats the point of having a lot of spindles).
I thought that once Commvault starts to write a stream to a mount path, it won't stop until the stream stops, or the mount path is full?
Pretty much all the Commvault benchmark tools for maglib seem to measure sequential throughput which doesn't seem to help much with re-hydrating dedupe data to tape.
Paul
From: commvault < at > yahoogroups.com [commvault < at > yahoogroups.com] on behalf of Troy Whistman [troy.whistman < at > gmail.com]
Sent: 07 February 2012 8:43 PM
To: commvault < at > yahoogroups.com
Subject: Re: [commvault] DASH Synthetic Full - Streams?
Paul,
A DASH synthetic full (dedupe-aware synthetic full) doesn't actually read any streams of data off the Media Agent; that's what makes it so fast. It simply updates the index files and the pointers in the dedupe database to signify that a full has been performed. No data blocks are actually read from the disk library (dedupe store) or the client. All the work happens on the media agent, and once the DASH Synthetic full completes, a new cycle begins (the DASH full 'acts like' a normal full in that any older cycles become eligible for pruning based on your aging rules as applied during the next data aging operation).
If I misunderstood your question, let me know. What did you mean by "re-hydrate to tape" in this context??
On Tue, Feb 7, 2012 at 2:35 PM, Paul Hutchings <paul.hutchings < at > mira.co.uk ([email]paul.hutchings < at > mira.co.uk[/email])> wrote:
Can anyone tell me whether a DASH Synthetic Full can be configured to write to more than one stream?
I'm asking as I believe that an aux copy will only ever read from the same number of streams that wrote the backup.
So in the situation where you most want to use a DASH Synthetic Full, which is a backup of a large file server with data that doesn't change very often, you can only re-hydrate to tape using a single stream, which seems a very inefficient use of all the spindles in the MA.
Thanks,
Paul
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