Slow backup on a locally attached external Ultrium 460

[Tony Nava]

I am running a backup from an RP7420 to an external locally attached Ultrium 460. I am only getting about 15gb/hour. What could be the problem? Shouldn't I be getting about 200gb/hour? Is there a problem with the block size, drivers, or firmware?

[Kurt Beyers.]

Tony,

The throughput depends on the type of data you are sending to the LTO drive (eg database files of a few GB each or an ordinary file system backup with a lot of small files). And what is the throughput of the SCSI controller?

Check the tape drive once with LTT.

What throughput do you reach when you take a backup to /dev/null?

best regards,
Kurt

[Leif Halvarsson_2]

Hi,
Which backup tool do you use ? Some of the standard HP-UX utilitys is perhaps not optimal for high-end devices as Ultrium 460. But, most likley, the bottleneck is with the file- and disksystem. You need a very fst disk system and a resonable average filesize to stream a such device.

[Stuart Whitby]

There are a few possible problems. You tell us what server hardware you're using, but nothing about the disks behind it. RAID 5 are among the fastest to read, but not for small files. Make sure disk and tape are on different SCSI buses (ideally different backplanes), that you have an appropriate tape blocksize for the files you're writing, that the network (for file metadata, depending on your backup app) isn't causing the bottleneck etc.

[Andrei Lica_1]

1. upgrade firmware on tape ( optionally on other components ) is almost always a good idea. Use HP provided L&TT software
I had same issue with my Ultrium3 tape and after the upgrade the speed increased from some 15MBps to ( sometimes ) 60-80MBps
2. I have used a INPUT block size of 64k when reading from RAID5 controllers ( works both RAID 6400 family and EVA5000 ) , speed increased 2-3 times. These controllers have a 64k default and maximum internal stripe size.
3. Use 256KB block size to write/read to/from tape drive. I've found that optimal for Ultrium2/3 drives ( at least in combination with dd )
4. Use a good backup tool - not those included in hp-ux. the defaul unix utilities are poor performers on hp-ux

Be aware that these tricks may not be valid for every RAID controller/tape drive combination or other factors ( filesystem or raw device, LVM setup ,etc )
Andrei