Tape Libraries and Drives
cancel
Showing results for 
Search instead for 
Did you mean: 

Write rate onto a DLT7000

SOLVED
Go to solution
Peter Day_3
Occasional Contributor

Write rate onto a DLT7000

Guys,
Can anyone please tell me what write rates you would expect to see on the following -

Storagetek 9710, with DLT7000's.
10/100LAN

This is currently being backed up via Legato.

The system being backed-up has approx 35-40Gb, and is taking approx 10Hrs

Any helpful hints would be very welcome.

Thanks,
Pete
9 REPLIES
Stefan Farrelly
Honored Contributor

Re: Write rate onto a DLT7000

A DLT7000 is capable of around 30 MB/sec, which is just over 100 Gigabytes in an hour. If youre only getting 3.5/4GB/hr then you are running at around 3.5/4% of max speed!

Your limited by network though, even 100LAN is only 12MB/s - which is 43GB/hr - so youre backup should still only take 1 hour.

Is this LAN shared by others users ? If so they will slow down your backup considerably. I would look into Legato - these high level backup programs have all sorts of performance tuning options to increase your backup speed - its unlikely to be the HP server causing the slow throughput.
Im from Palmerston North, New Zealand, but somehow ended up in London...
Jean-Luc Oudart
Honored Contributor

Re: Write rate onto a DLT7000

Pete,

we now have UltriumII and rate are much much better !
On Unix, with a mix of large files and smaller files we used to have 1 rate of 22-25Gb/Hour (direct attached DLT7000).
Over the network, for W2K servers , around 15Gb an hour but this will depend on the network load and the amount of small files vs large files.

Jean-Luc
fiat lux
Jean-Luc Oudart
Honored Contributor

Re: Write rate onto a DLT7000

Stefan,

as far as I remember a DLT7000 is only able of 35Gb/hour.
100Gb an hour is likely to be SDLT speed.

Jean-Luc
fiat lux
Mark Grant
Honored Contributor
Solution

Re: Write rate onto a DLT7000

Peter,

It's worth checking your network card is running at full speed and full duplex and the network switch is too. Use "lanadmin -x " to check.
Never preceed any demonstration with anything more predictive than "watch this"
doug mielke
Respected Contributor

Re: Write rate onto a DLT7000

I too get dismal speed out of our DLT 7000s.

HP's position is that it's the delivery speed to the device(it's on a 100 mg network as well)

They tell me the 7000 buffer empties, then tape stops, then has to reposittion before stating again. I think I see this on my activity lights, in that they flash for 4 seconds or so, then wait for nearly 10 secs. before starting again, This see saw effect has been impossible for me to fix up to now, and we're just going to dump all the 7000s.
Mark Grant
Honored Contributor

Re: Write rate onto a DLT7000

With DLT's, keeping the tapes streaming is vital otherwise you will get very slow data rates and your drive will fail fairly quickly.

This means your systems must deliver the data fast enough and the network must fast enough too. I would make sure your backup runs when there is really light load on your network and system if you can. Consider having a dedicated backup lan.
Never preceed any demonstration with anything more predictive than "watch this"
Leif Halvarsson_2
Honored Contributor

Re: Write rate onto a DLT7000

Hi,
The transfer rate of a DLT7000 is 10MB/s 2-1 compression 5MB/s native.

A very common problem with slow performance is if backing up a very large number of small files. A such problem has nothing to do with the tape drive, it is related to the disk or filesystem.
Bernhard Mueller
Honored Contributor

Re: Write rate onto a DLT7000

Pete,

using OmniBack to write a filesystem backup to a DLT7000 provides a (measured) throughput to tape of about 9MB per second.

This is somewhat dependend on the size/number of files, i.e with UNIX filesystems such as /usr, /var etc. you only reach about 8MB/sec.

I am not sure if you would find similar perfomance with Legato, with dd or cpio you will not be able to get it streaming nicely and hence will be stuck at 1 or 2 MB per second.

Regards,
Bernhard
JJ Urich
Frequent Advisor

Re: Write rate onto a DLT7000

As stated earlier, DLT7000 trafer rate is 5 megabytes/second, which is 18Gbytes/hour or 36Gbytes/hour with 2:1 compression.

Legato is most definetely able to keep you drive streaming providing the network, disk and cpu loading on both your backup server and backup client are up to the task. Legato does has a number of tuning parameters. It has been a few years since I've used it though so don't have them at my finger tips. To verify your network speed is truely 100 MB/s between your backup server and backup client do a ftp of /stand/vmunix to /dev/null. Do both a put and get, or perferable do two puts at the same time but from different directions. You can turn hash on as well with ftp and should see the # signs flying by. Use this as a rough test of 100MB/s full duplex connections. You can also down load and run netperf complements of Rick Jones if you really want to measure your bandwidth (http://www.netperf.org).

One fault of legato and omniback is backing up large f/s with lots of small files. I had similar problems backing up a 100G f/s full of user accounts. The disk was an autoraid 12H. I ended up having to split the backup into multiple objects so that I could get more disk agents to pound the file system. I used glance to see that my disk was not at 100% utilization and kept cranking up the parallel objects until my disk was pegged at 100%. As the others have suggested, keep an eye on your DLT drive as well. It should be flashing (writing), if it isn't a majority of the time, you are not streaming and need more data.

Regards,

JJ
I used to have spare time, then I had kids.