Old problem: backup on dat drive too slow

[Tim_Taler]

Hi,

another question regarding the speed problem:

On BE 11d on SBS 2003 Standard SP2, Adaptec 29160 and DDS-3 tape drive (Certance STD224000N) it's not possible to compress data and achieve more than 1 MB/s.

On my system everything is patched, I use latest BE driver for tape drive, SCSI controller has latest BIOS, tape drive has latest firmware, Server has latest BIOS. Within SCSI controller BIOS the settings are as recommended by Symantec. Controller and tape drive are connected with a 50cm cable with 3 connectors, controller sits on the first, drive on the last connector. On tape drive compression is enabled (dip switch 6 = off), SCSI ID is set to 6, jumper for termination is set. The server has 4 GB of memory, 2 SATA HD with 160 GB each are configured as RAID 1. Server and BE have the latest patches.

For the purpose of testing I backed up 8 quite big Files that make together 1,48 GB. They are database files and should be compressable.

Within the test backup job I tried these settings: use drive compression if possible, don't use compression, use software compression or none. For the tape drive I tried for block and buffer size, buffer count and water mark 8/32/10/7, which is standard by BE. I tried also completely different values: 32/128/20/10. Server disks are defragmented automatically once a week. I tried MS drivers for type drive - no effect. I updated them - no effect. I changed several settings in 29160 controller - no effect. I set dip switch 6 to on - no effect. In BE and in NTBACKUP speed remains about 1 MB/s.

In none of these cases anything changed neither speed nor or compression ratio, regardless what I configure, everything remains the same.

What could be a hint is that device statistics reports recoverable write errors after each test job (about 10 per job - read errors only 1 in total and 6 search occurences). Another hint might be, that device manager (of Windows) on the property page says "compression capable = yes" but "compression enabled = no" (regardless whether switch 6 is on or off). During the tests I altered the compression state with a tool from Certance (TapeRX).

I worked on that for 12 hours now, so here is my question to you: what else could be done to achieve more speed? Are all these settings you can make in BE really functional or are they pure fake?

The point is, that I cannot use my backup system - it is to slow and there are about 15 GB of data, which do not fit on one cartridge because there is no compression. It is frustrating that the most unsecure and unpredictable thing with computers allways have been just tape backups.

I really would appreciate if someone had some ingenious ideas.

Regards,
Tim

[CraigV]

I tend to up the buffer in Backup Exec to 1MB, which seems to make things a bit quicker.
Have you checked if there was a change when using a different SCSI cable?
Could your speed problem not be due to the SATA drives? And what speeds do you get to disk as a matter of interest?

[Larry_Fine]

You state you are unhappy with 1 MB/s.  What do the drive specs or documents say it is capable of?  According to http://en.wikipedia.org/wiki/DDS-3 that generation of drive is capable of 1.1 MB/s.

regarding compression: Within BE's drive properties is compression enabled?  When you run a backup using a compression setting of "hardware (if available, otherwise none)", what does the job log show?

[teiva-boy]

 1MB/s is roughly 60MB/min which is how BE generally shows speeds right?  That seems about on par with DDS speeds.

If anything, I would have put the tape drive on the next available SCSI port, and terminated the next one.  Where as you have it at the end with blanks inbetween?  SCSI termination these days are greek for many that are no familiar with it, and it tends to get misconfigured more often than not.  Darn those terminators!  

[Tim_Taler]

 First of all: thanks to you all for your efforts!

@CraigV
I tried your suggestion and increased the buffers to 1MB, but this did'nt change anything. But as I learned from the other commentators my 1 MB/s is that what DDS-3 is capable of. I could swear of having read something about 2-3 MB/s.

@Larry Fine and teiva-boy

Indeed, Wikipedia is talking about 1,1 MB/s. So I will have to accept that. Regarding compression: I enabled compression within BE drive propterties. And if enabled the log as well reports that ("if available, otherwise none"), although it obviously does not take place.

Meanwhile I could boost my backup speed up to about 70 MB/s - with software compression (which I thought I already had tested). Logs afterwards correctly report that software compression was used and even the amount of data fitting on one tape has increased up to 17 MB. After all I learned from you I should be happy with that.

Still interesting for someone else might be why there is no hardware compression. If someone has any idea let me / us know.

Thanks again.

Regards,
Tim

[Tim_Taler]

 First of all: thanks to you all for your efforts!

@CraigV
I tried your suggestion and increased the buffers to 1MB, but this did'nt change anything. But as I learned from the other commentators my 1 MB/s is that what DDS-3 is capable of. I could swear of having read something about 2-3 MB/s.

@Larry Fine and teiva-boy

Indeed, Wikipedia is talking about 1,1 MB/s. So I will have to accept that. Regarding compression: I enabled compression within BE drive propterties. And if enabled the log as well reports that ("if available, otherwise none"), although it obviously does not take place.

Meanwhile I could boost my backup speed up to about 70 MB/s - with software compression (which I thought I already had tested). Logs afterwards correctly report that software compression was used and even the amount of data fitting on one tape has increased up to 17 MB. After all I learned from you I should be happy with that.

Still interesting for someone else might be why there is no hardware compression. If someone has any idea let me / us know.

Thanks again.

Regards,
Tim