Veritas-bu

Re: [Veritas-bu] T2000 vaulting performance with VTL/LTO3

2007-11-21 16:07:23
Subject: Re: [Veritas-bu] T2000 vaulting performance with VTL/LTO3
From: "Marianu, Jonathan" <JM7640 AT att DOT com>
Date: Wed, 21 Nov 2007 12:48:23 -0800

My recollection is that during duplication from VTL to tape , it uses the mpx originally set in the policy unless it is throttled down by the vault policy but you can’t increase it. The MPX is what is so interesting to examine in truss because I observed that any multiplexing will impact the duplication speed.

 

This is impact more pronounced though when you are mixing slow and fast clients together because the fragments are not spread out evenly on the virtual tape and bptm has to rewind the virtual tape and reread, causing a delay to physical library which is torture on the physical tape drive

 

Then I observed that a higher MPX led to a slight improvement in duplication speed. I would use 24-32

However there are other tradeoffs. In the end we decided to not use VTL for network client backups for the new master server environment model.

A problem with VTLis that a slow client backup will hold onto the vritual media preventing me from using it for duplication. This impacts the RPO of other clients backups. DSU does not have that issue.

We use 64TB EVA file systems per network media server which give pretty even performance and we use vxfs.

One outstanding issue with file systems that you don’t have with VTL is fragmentation Another benefit of VTL is that I have a media server dedicated to writing the backups and another media server dedicated to duplicating backups.

.


__________________________________________
Jonathan Marianu (mah ree ah' nu)
AT&T Storage Planning and Design Architect
(360) 597-6896
Work Hours 0800-1800 PST M-F

Manager: David Anderson
(314) 340-9296

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