Tape Backup performance issue with a PE2950 with MD1000 RAID 5arrays attached via Perc5/e controller.

[Kevin Davidson]

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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