Simon,
Firstly, have you tuned SIZE_DATA_BUFFERS_DISK and NUMBER_DATA_BUFFERS_DISK?
Other than that, performance management when writing backups to disk is very
different to tape. Writing multiple streams to a single DSU or volume group
can work well, until you hit a magical threshold and suddenly performance
dives through the floor. Although writing a backup to disk is a sequential
write operation, if you write more than one stream in parallel, it suddenly
becomes random writes from the disk subsystem's perspective, which can have
major performance implications.
You also need to look at what other activity is happening in the EVA at the
time, and particular on the same volume set (or RAID set, or whatever
terminolgy is used). You could also look at performance on the disk
controller/s and interface/s.
Aside from all that, you've got your work cut out trying to get any disk to
outperform an LTO3 (performing sequential writes). Despite what various
vendors tell you, tape is very well suited to backup workloads. It was
designed for it! Backing up to disk is better suited to slower clients that
can't send data to the media server fast enough to keep the tape drive
streaming.
That's all my opinion, and I might be a bit biased ;)
Cheers,
Dean
On 9/11/06, WEAVER, Simon <simon.weaver at astrium.eads.net> wrote:
>
> *All*
> *I have been testing DSU backups, and must admit I have not been impressed
> with the throughput to disk.*
> **
> *I ran a particular job over the weekend. Setup as follows:*
> **
> *LAN Client normally takes 2-3hours via Tape LTO3 HP ESL*
> *Created a Disk on my Master Server*
> *Configured a DSU with phase 2*
> *Set the policy to use the newly created storage unit.*
> *Let the backup run.*
> **
> *The backup took 4 hours (just over). However, writing to tape (I guess
> when it does its duplication) took under 1 hour.*
> **
> *The Disk that was presented to my Master is a VDISK from a HP EVA using
> Fibre SCSI disks. Essentially the HP EVA is a large SAN, and you can create
> volumes and present them to a specific Server.*
> **
> *Have I missed something here, or is it a case that my Tape Setup (that is
> all fibre channel connected) is actually running better than I thought.*
> **
> *Thanks*
>
>
> *Regards*
>
> *Simon Weaver
> 3rd Line Technical Support
> Windows Domain Administrator*
>
> *EADS Astrium Limited, B23AA IM (DCS)*
> *Anchorage Road, Portsmouth, PO3 5PU*
>
> *Email: **Simon.Weaver at Astrium-eads.net* <Simon.Weaver at Astrium-eads.net>
>
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