Ultrium 960 - length of backup

[Beverly Renkema]

System: HPUX 11.i - rp7420
On a nightly basis we run an fbackup of our databases - roughly 219 Gb total in 5 files.

When we run this backup to an Ultrium 3 tape in an Ultrium 960 tape drive, it takes 2 1/2 hours for the backup to complete.

This seems like a long time for that amount of data, but I have nothing to base it on because this is our first 960 drive.

Does this seem a resonible amount of time for this size backup or should I start digging into our configuration?

[Steven E. Protter]

Shalom

Its not a long time at all for 219 GB.

If you are database down and have the disk, you could close the backup window shorter by copying disk to disk or using OnlineJFS snapshots to bring the db up faster.

I would check the following easy things.

1) Make sure the tape drive is alone on its scsi chain. It should be the only device and not shrae the chain with disk. This will slow it down.

2) run ioscan and make sure there are no scsi id issues.

3) Make sure the drive is cleaned properly once every 90 days or when the indicator flashes for it.

SEP

[Josiah Henline]

The SCSI card that you are using may not be fast enough or set to a fast enough setting to utilize the full potential of your new tape drive.

Most newer SCSI cards have settings that can be modified from the BCH.

[Josiah Henline]

Run an "ioscan -fn" and paste the results of the SCSI card and tape drive.

[James R. Ferguson]

Hi:

Unless you have modified the default parameters in the configuration file used with 'fbackup' you are probably going to see 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...

[Dave Hutton]

What backup software are you using? I know theres some files you can edit for Netbackup with buffer size. Once those are tweaked my throughput greatly increased.

I'm assuming its direct attached? or is it san?

[Sanjay_6]

Hi,

It would also depends on the disk performance (disks on which this data is stored). The drive specs are as below,

http://h18006.www1.hp.com/products/storageworks/ultrium960/specs.html

The specs say you can get transfer rates of upto 576 GB/hr. But you should also check this answer from the FAQ,

http://h18006.www1.hp.com/products/storageworks/ultrium960/qa.html#4

This is the whitepaper that is referred in the previous answer,

http://h71028.www7.hp.com/ERC/downloads/5982-9971EN.pdf

Hope this helps.

regds

[Bill Hassell]

Although the specs say the data rate is more than 500 Gb/hr, that is not accurate because it requires special data. If you can ensure that all your database files have highly repetitive patterns that are lengthy, say 50% of each data record, you may see an effective rate of more than 500 Gb/hr. I say effective because the drive only stores data at about 200 Gb/hr on a tape that only holds 400 Gb. Now if that looks strange (compared to the specs), virtually all marketing departments double their numbers with a disclaimer that the data must be 2:1 compressible.

The tape still only stores 400 Gb. By replacing long strings of repeating characters with a special code sequence, the 400 Gb limit appears to be larger. The reality is that the 400 Gb can be expanded back to 800 Gb when restored.

Now your 219 Gb will fit just fine on the tape and the backup can be performed in about 60 minutes or less UNLESS:

1. your computer is too slow
2. your disks are too slow
3. your backup software is too slow
4. your system is busy
5. your tape drive is on a slow SCSI card

Oops. that's a lot of possibilities. Now the rp7420 should be up to the task as long as you have more than 2 processors (more than 4 would be ideal). The disks you are backing up may not be able to sustain 80 Mb/sec (over 160 Mb/sec if your data can be compressed). Since you are using fbackup, you're halfway there. Add the -c configfile to your backup command. Backups will always be slowed if there are active processes fighting to get disk I/O's from fbackup. And if the tape drive is not on a dedicated Ultra320 (no other devices on the card), it will be sharing I/O bandwidth with other devices.

All this is to point out that the Ultrium 960 is a VERY high performance tape drive, so fast that it has a special 'slowdown' feature called DRM (Data Rate Matching) that reduces the tape to 27 Mb/s when necessary to prevent data underrun conditions. Your backup performance is about 27 Mb/sec so you are running at the slowest speed the tape drive allows without resync operations. In the link above, the PDF document has a large section on performance concerns.