Tape Backup performance issue with a PE2950 with MD1000 RAID 5arrays attached

[Rönnblom Janåke /Teknous]

Hi,

First I don't think you would gain anything by replacing the LTO3
drives since your not pushing them to their limit today.

Second. What kind of files are stored on the disks? Are they small
or large? Millions of them or only a few thousand? Do you use the
SATA disks for backup to disk?

Have you read the NetBackup Performance Guide? Which version
of NetBackup are you running?

http://seer.entsupport.symantec.com/docs/307083.htm

You might need to tune BUFFER_SIZE among a few things
and then probably the Linux kernel also. You could also measure
the speed to the LTO3 drives with dd and different buffer sizes
to determine the sweet-spot!

Good luck!

-J



"Gary Mansell" <Gary.Mansell at ricardo.com> writes:
>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
>



=====================================================
Janåke Rönnblom
IT avdelningen, Teknous, Skellefteå Kommun
Assistentgatan 23
931 77 Skelleftea (Sweden)
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