Re: Performance degradation on DLT tapes

Ok. Before you can nail down your tape drive as the cause of the problems I
think you should setup at least a small disk buffer pool. See what happens
when you go to disk first.

Backing up straight to tape is generally a bad idea, disk is usually fast
than tape and the number of client sessions is limited by the number of tape
drives available. There are instances where going straight to tape works out
very well. I've seen people back up straight to tape when backing up large
files and databases. The constant stream of data should allow the tape drive
to get up some steam and really start moving.. particularly a DLT tape which
will move into it's streaming mode (provided that the data-in is fast
enough).

Take a look at the type of files that you are backing up. Are these lots of
small files <1-10Kbytes? If so then you will suffer a performance
degradation.
When ADSM has to backup lots of small files there's going to more overhead
involved.

It's worth going through the ADSM Server readme on typical performance
issues...

  2.4 Performance issues
  ----------------------

    There are a large number of variables that can effect NT and ADSM
    for Windows NT performance.  Improving performance usually involves
    performing a detailed examination of key system components to
    determine where the bottlenecks are on both the ADSM server and the
    ADSM client machines.

    Performance monitor, which ships with Windows NT, is an excellent
    tool to help determine where system bottlenecks are.

    In general, adding RAM, using the fastest available SCSI disk drives,
    SCSI controllers, network interface cards, and CPUs as well as
    SMP machines will all improve the performance of NT and ADSM for
    Windows NT.

    Next to system hardware, the number and size of client files has a
    big impact on ADSM performance.  The performance when tranferring
    small files is lower than when transferring large files.

    For example, using a 133MHZ pentium, FAT file system, local ADSM
    client with no compression, and named pipes to a disk storage pool
    throughput has been measured at:

                                     File Size
    Throughput          1KB      10KB    100KB     10MB
    KB/Sec                57       445     1280     1625
    GB/hr               0.20      1.53     4.39     5.58

    A simple test using ftp to transfer a set of files from the ADSM
    client machine to the ADSM server machine can provide a reference
    as to the network performance between two machines.  In general,
    when using ADSM to transfer the same set of files ADSM should not
    perform much differently than FTP.

    The choice of file systems also comes into play with regard to
    performance. NTFS compressed drives should not be used to hold
    ADSM disk volumes (database, recover log, or disk storage
    volumes).  On the client side, backing up NTFS data can be
    significantly slower than backing up FAT data. On the server side,
    use of NTFS is also slower than using FAT.  The tradeoff is that
    NTFS has security and is more robust than the FAT filesystem.

    There are many good sources of information regarding NT performance
    improvement. The Windows NT resource Kit provides good coverage of
    of the use of performance montitor for example as does a number
    of other NT related books.



> -----Original Message-----
> From: Alexandre Bicas Caldeira [SMTP:abicas AT SERVICE.COM DOT BR]
> Sent: Monday, September 06, 1999 8:12 AM
> To:   ADSM-L AT VM.MARIST DOT EDU
> Subject:      Re: Performance degradation on DLT tapes
>
> Dear Nathan,
>
> > Like ADSM Server Platform and Version. What type of hardware? Are you
> > backing up straight to tape? or are you migrating from a disk buffer?
>
> ADSM Server Platform: Windows NT sp4
> ADSM Version:   3.1.2.40
> Backup: Straight to tape.
>
> > I did have a DLT throughput issue once with ADSM V3 on Windows NT and
> found
> > the culprit to be a bad SCSI driver. I updated the SCSI drivers.
>
> I also have a low performance writing on an IBM 3595 with 2 optical
> drives: 0.3
> MB/s; that is why I decided to do my backup on DLT tapes.
>
> _______________________________________
> Alexandre Bicas Caldeira - abicas AT service.com DOT br
> Service IT Solutions - http://www.service.com.br
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