Tape Backup performance issue with a PE2950 with MD1000 RAID5arrays attached via Perc5/e controller.

Fri Oct 3 08:18:07 CDT 2008

Thanks for taking the time to respond - FYI, I take a Full Backup at the
weekends but then in addition I take Incrementals every evening and
lunchtime differentials every day of the working week. Obviously the
incrementals and differentials can be done in a reasonable time window.

The idea of taking snapshots is a valid one but if it takes longer to
backup the snapshot  than the weekend window then I will impinge on the
performance of my Fileserver during the working day.

On Fri, 2008-10-03 at 12:44 +0100, Kevin Davidson wrote:

> If you cannot work around your bottleneck problems I would be worried  
> about getting good backups that take that long if you are backing up  
> live data. Obviously I don't know your application and if weekly  
> backups of live data is adequate or if you are able to guarantee the  
> data is not modified during your 2 day backup window. .
> 
> Have you considered swapping to ZFS or using LVM to create (daily)  
> snapshots of your data so you can
> a) have stable tape backups of static data
> b) can backup to tape more frequently during the week
> c) can quickly recover data from previous days
> 
> This is obviously lighter weight than disk to disk to tape, but faster  
> as there is no data copying for creating snapshots.
> 
> -- 
> Kevin Davidson
> Sent from my iPhone
> 
> indigospring :Making Sense of IT
> w http://www.indigospring.co.uk/
> t 0870 745 4001
> 
> On 3 Oct 2008, at 11:28, "Gary Mansell" <Gary.Mansell at ricardo.com>  
> wrote:
> 
> > Hi,
> >
> > My company has a Dell PE2950 with 1 tray of MD1000 300GB SAS drives in
> > RAID5 (3.5TB) and 1 tray of 750GB SATA drives in RAID 5 (9TB). They  
> > are
> > both attached via a Perc5/e SAS controller card. All volumes are
> > configured with LVM2 partitions and ext3 filesystems. We backup this
> > data with an Overland Neo200 with 2x LTO3 tape drives attached to the
> > server with a dual ported LSI ultra 320 SCSI card and Netbackup
> > Software.
> >
> > We generally get a backup performance of about 35MB/s. This equates to
> > about 50 hours with two drives and is hence our entire weekend backup
> > window.
> >
> > My first question is that this seems rather slow: the reason that I  
> > say
> > this is that a noddy dd read test to /dev/null shows a raw sequential
> > read speed from the MD1000 arrays of about 200MB/s. Now I realise that
> > this is bypassing the ext3 filesystem to an extent but there seems  
> > to be
> > quite a discrepancy here. The only other things that I can think of  
> > that
> > might be affecting this is disk fragmentation on the filesystems. Is
> > this to be expected, what speeds do others of you get from similar
> > configurations? Where is the bottleneck likely to be here as the LTO 3
> > tape drives are quoted as 54-160MB/s with compression!!!
> >
> > We are looking to expand this storage capacity by adding another  
> > MD1000
> > of 1TB SATA drives in RAID5 (13TB). This will either daisy chain off  
> > of
> > one of the above tray's Perc5/e channels (not great for performance),
> > or, if we chose to move the backup system to a separate dedicated
> > server, we can use the freed SCSI card slot for another dedicated
> > Perc/5e SAS controller. The problem that I see with this is that I  
> > feel
> > that the backup performance will degrade if the server is backed up  
> > over
> > the network rather than locally. Is this likely?
> >
> > We could install LTO4 tape drives in our Neo200 as they are rated with
> > 50% faster performance of LTO3 but I am concerned that as we are not
> > hitting the performance limits of the existing LTO3 drives, we may see
> > no faster performance.
> >
> > I would really appreciate people's comments on my configuration and
> > recommendations as to what the best solution would be to increase my
> > storage 200% but still to be able to back it up over a weekend.
> >
> > Best Regards
> >
> > Gary Mansell
> >
> >
> >
> >
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Gary Mansell 
Team Leader - Technical Computing 
Ricardo UK Ltd. 
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