[Veritas-bu] Fast backup to tape but slow backup to disk on NBU 5.1MP3

For a 6 drive 10 raid, I got about 140MB/sec reads & 95MB/sec writes. 
It's a shame that it takes so many disks to get good write performance
on a redundant raid.

These are all 400GB SATA disks.

On 8/14/05, Eric Ljungblad <Eric.Ljungblad AT copleypress DOT com> wrote:
>  
>  
> 
> Good testing, 
> 
>   
> 
> Have you tried RAID 10 / (1/0)  or tried  (0+1) ? 
> 
>   
>  
>  ________________________________
>  
> 
> From: veritas-bu-admin AT mailman.eng.auburn DOT edu
> [mailto:veritas-bu-admin AT mailman.eng.auburn DOT edu] On Behalf
> Of Dean
>  Sent: Sunday, August 14, 2005 5:15 AM
>  To: Tim Berger
>  Cc: Matt Clausen; veritas-bu AT mailman.eng.auburn DOT edu
>  Subject: Re: [Veritas-bu] Fast backup to tape but slow backup to disk on
> NBU 5.1MP3 
>  
> 
>   
> 
> "Matt, writing multiple concurrent streams to the same set of disks may
>  be hurting performance.  One at a time may yield better results."
>  
>  I believe Tim's got it right. SATA is best at serial writes. If you feed it
> two or more streams, that is effectively random writes, and performance
> suffers badly. 
>  
>  
>  
> 
> On 8/12/05, Tim Berger <tim.berger AT gmail DOT com> wrote: 
> 
> Matt, writing multiple concurrent streams to the same set of disks may
>  be hurting performance.  One at a time may yield better results.
>  
>  I'm in the process of building out some staging servers myself for nbu
>  5.1 - been doing a bunch of bonnie++ benchmarks with various configs
>  for Linux using a sata 3ware controller.
>  
>  On fedora core 3 (I know it's not supported):
>  
>  Raid5, 5 disks I got ~30MB/sec writes & 187MB/sec reads.  Raid 50 with 
>  striping over 3 4-disk raid5's got 49MB/sec writes, 120 MB/sec reads.
>  For raid0, w/10 disks, got a nice 158 MB/sec writes, and 190MB/sec
>  reads.
>  
>  I'm partial to raid5 for high availability even with poor write 
>  performance..  I need to stream to lto3, which tops out at 180 MB/sec.
>  If I went with raid0 and lost a disk, then a media server would take a
>  dive, backups would fail, and I'd have to figure out what data failed 
>  to make it off to tape.  I'm not sure how I'd reconcile a lost dssu
>  with netbackup.  If I wanted to to use the dssu's for doing synthetic
>  fulls, then that further complicates things if a staging unit is lost.
>  
>  Any thoughts on what the netbackup fallout might be on a dssu loss?
>  
>  Even though it's not supported yet, I was thinking of trying out
>  redhat enterprise linux 4, but I'm seeing really horrible disk
>  performance (eg. 100MB/sec reads for raid5 vs the 187MB/sec on fc3). 
>  
>  Maybe I should try out the supported rhel3 distribution. ;-)  I
>  don't have high hopes of that improving performance at the moment.
>  
>  On 8/10/05, Ed Wilts <ewilts AT ewilts DOT org > wrote:
>  > On Wed, Aug 10, 2005 at 12:43:39PM -0400, Matt Clausen wrote:
>  > > Yet when I do a backup to disk, I see decent performance
>  > > on one stream (about 8,000KB/s or so) but the other streams will drop
> to 
>  > > around 300-500KB/s.
>  > >
>  > > NUMBER_DATA_BUFFERS = 16
>  > > NUMBER_DATA_BUFFERS_DISK = 16
>  > >
>  > > SIZE_DATA_BUFFERS = 262144
>  > > SIZE_DATA_BUFFERS_DISK = 1048576 
>  > >
>  > > and I see this performance on both the master server disk pool AND a
>  > > media server disk pool. The master server is a VxVM concat volume set
> of
>  > > 3x73GB 10,000RPM disks and the media server is an external raid 5
> volume 
>  > > of 16x250GB SATA disks.
>  >
>  > I don't believe you're going to get good performance on a 16 member
>  > RAID5 set of SATA disk.  You should get better with a pair of 8 member
>  > raid sets, but SATA is not fast disk and large raid 5 sets kill you on 
>  > write performance.  If you're stuck with the SATA drives, configure them
>  > as 3 4+1 RAID5 sets and use the 16th member as a hot spare.  You'll have
>  > 3TB of disk staging instead of about 3.8TB but it will perform a lot 
>  > better.
>  >
>  > --
>  > Ed Wilts, Mounds View, MN, USA
>  > mailto:ewilts AT ewilts DOT org
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>  >
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>  >
>  
>  
>  --
>  -Tim
>  
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> 
>   


-- 
-Tim