topic DDS Backup - Slow in Disk Enclosures

DDS Backup - Slow

Faizer — Wed, 30 Jul 2003 13:18:48 GMT

Hi Gurus,
I have a newly installed dds4 tape drive on my rp7410 server.
I used a DDS4 tape to backup a mount point having 23 GB of Data and it took 9 hours.
Definitely this is not acceptable by ant standards.
What could be the problem
Thanking you in advance
best regards
Faizer Jameel

Re: DDS Backup - Slow

Eugeny Brychkov — Wed, 30 Jul 2003 13:50:17 GMT

If you're backing up compressed data then 23GB is ok. Slow performance could be because of hardware problems, but could be because of block size backup utility uses.
For first please check drive with LTT http://h18006.www1.hp.com/products/storageworks/ltt/index.html , for second go to your backup application/device setup and increase block size (from 2K to 4K or 8K) and try backing up again and check time
Eugeny

Re: DDS Backup - Slow

Tim D Fulford — Wed, 30 Jul 2003 14:47:31 GMT

23GB in 9 hours is .75 (ish) MB/s some older SCSI busses do this!

What are you backing up (a database, flat files etc) & how (tar, cpio, dd database program...)?

If you are backing up things either it is slow reading it from the disk.
o So a disk layout that is not suited to sequential type reading,
o processes blocking access to file,
o the bus is flooded with other disk activity.
Or it is slow writing to the tape,
o if there are multiple devices there may be a buss bottle neck,
o the tape may be duff so there are many re-writes on the tape,
o the SCSI bus is simply slow.
o maybe you are doing it remotely so the LAN is slow....

You can check out to various degrees the above using LTT tools and you may also want to check out STM (mstm, or xstm)

Regards

Tim

Re: DDS Backup - Slow

Keith Bevan_1 — Wed, 30 Jul 2003 14:50:57 GMT

Faizer Jameel,

I am convinced the source of the problems are probably as per the previous advice, however, you may also wish to check that the tape read/write heads are not dirty and may require cleaning.

I have experienced this before when backups have occasionally completed in times longer than expected.

Check the clean light on the front of the drive, if it is activated then use an approved cleaning cartridge.

Keith

Re: DDS Backup - Slow

Leif Halvarsson_2 — Wed, 30 Jul 2003 15:58:12 GMT

Hi,
What backup tool do you use ? tar or cpio is not very fast, try fbackup or ftio instead.

Is there a very large number of small files and is perhaps the disk system slow ? This will have a big impact on backup performance.

Re: DDS Backup - Slow

Faizer — Thu, 31 Jul 2003 05:04:42 GMT

Hi there
The data is on a VA7410 virtual array having 1TB of disk apce shred by 3 servers. These are connected to the servers using FC and the VA7410 having an out put of 2gb

I use SAM which in turns uses fbackup.
I backup Oracle 11.5.8 ERP applications suite inclusive of the data and the binaries.

The funniest thing is that I rebboted this server and tried the backup it finished in 2 hours the 20gb. Then again I tried another back
for another mount point having 20gb data. Again it took the same time. Then I tried a reboot and then the backup still 9 hours.

The drives do not indicate any indication for cleaning too.

Re: DDS Backup - Slow

Eugeny Brychkov — Thu, 31 Jul 2003 05:18:32 GMT

When there's a slow backup performance please do the following tests:
1. try backing up local disk. Check the time and calculate throughtput. This way you'll exclude SAN;
2. try dd'if VA data into /dev/null
time dd if=/dev/rdsk/cXtYdZ of=/dev/null bs=1024k
and note time. Post this time here.
We need to understand where bottleneck is - in the SAN or tape. I susupect that in the tape, as soon as did not notice you complaining about Oracle database performance.
For fbackup I would check patches... Try tar'ing!
Eugeny

Re: DDS Backup - Slow

Faizer — Thu, 31 Jul 2003 08:53:55 GMT

Well I tired a backup of a file system having 13gb of Data which resides on my internal 36gb harddisk.
This took 88 minutes.
best regards
Faizer Jameel