HP Ultrium 960 Internal Tape Drive

[mehul_3]

Hi all,
Oracle database is running on HP-UX11i O/S and database size is of 95GB and generally takes 3.20 Hrs to take cold backup using hp-surestore DAT40 drive.So, we are evaluting a product like HP Ultrium 960 Internal Tape Drive and I learned that backup rate is 281GB/hr.
My question is mentioned backup rate is really possible in real situation.
Pl, help me in this regards so that I can convince to my higher-ups.

Regards,
Mehul

[Steven E. Protter]

Shalom Mehul,

Theoretical backup rates never happen in real life. Real life systems have other things to do than backup, hence run slower.

SEP

[Bill Hassell · Accepted solution]

The actual speed of a backup device used to be limited by the device -- but with drives such as the Ultrium series, the tape drive is extremely fast and often limited by slow computer hardware and backup programs. The 960 requires 80 Mbytes/sec, which is an extremely large amount of data. It is faster than some disks can provide, and when individual files are being opened and closed, the disk rate is diminished.

Even with high speed disks and a quiescent system, the backup program may be extremely slow. tar, cpio, pax, dump, etc, are very rudimentary programs that simply open one file, read and write to tape, then close the file. At Ultrium speeds, this action can't keep up with the drive. You have no choice but to use a high performance backup program. fbackup is the only program that comes free with HP-UX and can provide a data stream of up to 6 files at the same time. You would have to use a config file even with the DAT40 drive for maximum performance.

Now the DAT40's maximum speed is only 11 Gb/sec (possibly 22 Gb/hr if the data happens to be compressible) so your 95Gb in 3.2 hours is 29 Gb/hr, a very high number! This means that a *lot* of your data is compressible and for an Oracle database, this generally means that the database isn't very full -- yet. As the data areas fill up, the compression ratio will drop dramatically and your DAT40 will max out at the 11 Gb/hr native rate (and tape capacity of 20 Gb).

The same will happen with the Ultrium. The maximum capacity of the tape is 400 Gb although the ads will constantly show 800 Gb with a footnote: (2:1 compression). Since you cannot control the content of the data, you can't assume the high number at all. The reality is that compression simply removes redundant data -- the tape still only holds 400 Gb. But for your 95Gb, that's more than adequate.

Now all of this leads up to actual performance. To reach the native speed of 80 Mb/sec (or 280 Gb/hr), the tape MUST be on a dedicated Ultra360 SCSI interface, and the disks must transfer data at more than 80 Mb/sec. And the processors (minimum of 4 CPUs) should be faster than 600 Mhz. With all of those constraints, you should be able to keep the Ultrium running at full speed using a high performance backup program like fbackup or Data Protector.

NOw the good news is that the Ultrium can adapt to a slower data rate (down to 27 Mb/sec or 97 Gb/hr using DRM or Data Rate Matching). Tape drives such as your DAT40 cannot do this so if the data is too slow, the DAT 40 has to stop, back up and resync which can degrade throughput from 1/3 to as little as 1/20 normal speed. So the Ultrium can keep the tape streaming at a slower speed which makes it much more versatile.

[mehul_3]

How to use config file with DAT40 drive for maximun performance.
Pl, urgent..

Thanks for support

Regards,
Mehul

[James R. Ferguson]

Hi Mehul:

Using the unmodified default parameters of the 'fbackup" configuration file is going to yield very poor performance. The manpages for 'fbackup(1M)' document the default settings which is what you will get in the *absence* of an explicily defined set.

These parameters are recorded onto the actual backup tape and are thus used for a 'frecover' session too.

Checkpoint records allow the salvage of a backup when a bad tape spot is detected, since the records contain information about the file being backed up. The 'filesperfsm' parameter controls the frequency with which Fast Search Marks (FSM) are written. Both checkpoint and FSM records affect performance. FSMs take a tape drive out of streaming mode thereby adding to backup time. Conversely, however, FSMs improve the time it take to recover a file from tape.

In general, if your backup consists of a high proportion of small files, increase the value for 'filesperfsm'. If your backup consists of a high proportion of large files, then decrease the 'filesperfsm' value.

A configuration file along these lines should work well:

blocksperrecord 4096
records 64
checkpointfreq 4096
readerprocesses 6
maxretries 5
retrylimit 5000000
maxvoluses 200
filesperfsm 2000

Regards!

...JRF...