Fine Tune LTO 5 Tape Drive

[agvonline]

Hi

I'm looking for some advice/guidance on getting the best performance out of my LTO 5 tape drive.

This is my setup:

HP 1/8 G2 LTO 5 AutoLoader - connected to...

HP DL360 G6 Server - via...

P212/256mb Smart Array Controller.

Then...

HP MSA2012i SAN - connected to...

another HP DL360 G6 - via...

HP 1800 8g switch.

There is also a HP 5308xl switch (with 1gb GBICs) connecting the two servers.

I have data stored on the SAN which I want to backup using the 1/8 G2 Autoloader, so the network/data route of this is...

MSA2012i -- HP 1800 8g -- DL360 -- 5308xl -- DL360 -- 1/8 Autoloader.

All network connections are 1gb.

I have Backup Exec 2010 G3. The default configuration for the LTO5 drive is used (64kb block size, 64kb buffer, 10 buffers, 0 high water). I also have 'Unknown Media Changer' set as Autoloader driver, and the latest Semantic DDI drivers for the tape driver.

As a test, to backup 18.3gb (34783) files of data, the data rate I get is 2,851mb/min.

I have done some tests increasing the block size and buffer count, but the best rate I can get is 2,890mb/min when I set block size and buffer count to 256kb. But is must be able to go faster than this...shouldn't it??

Any thoughts on this would be much appreciated.

Thanks

Andrew

[CraigV]

Hi Andrew,

If you're backing up files, that's a great speed to be getting to be honest.

Your biggest issue will come with data not being streamed to the tape drive fast enough for it to run at a constant speed. Under the tab where you get your buffer count etc., deselect the 2 options (can't remember them off-hand) as this might also give you a bit of a speed increase.

Thanks!

[agvonline]

Thanks for posting so quickly,

It's just from all the literature I've read, I feel it should go a little faster. Up to 4200mb/min perhaps.

The options you mention, do you mean Read/Write single block mode? I currently have those de-selected. 

[ZeRoC00L]

Copy some files/folders from the 2nd server to you Backup Exec media server and see how fast these files are copied. You will never get a faster backup speed than that.

[teiva-boy]

4200MB/min exceeds what you can pass from the SAN over your Gb link.  Not possible.

Move to a better SAN, leverage 10GbE or 4-8GB FC, and it maybe possible to achieve better rates.

Or backup to disk locally on your BE server (using some sort of DAS), then duplicate to tape.

[agvonline]

Ok, I've tried the following experiment.

I copied 17gb (35000) of files from SAN across network to backup server. This took approx. 10 minutes, but the speeds started at ~95mb/min but drifted down and down until ~25mb/min.

Anybody any ideas why this happens?

[ZeRoC00L]

Hard to say, but it can be load (during working day).
Small files are much slower than large files.

Create some large (1 Gb) files and try again, and post the results.

[agvonline]

I copied over a 4.5gb ISO file. The speeds were consistently good, ~100-105mb/sec.

Obviously this demonstrates the speed issues associated with copying thousands of files, but what I don't understand from my previous post is why the speed gradually reduces.

[CraigV]

...could also be your RAID level (some RAID levels are faster than others); also check that your NIC and switch ports are hard-coded to the fastest port speed both are mutually capable of. Might give you a bit of a speed advantage too.

[agvonline]

Yes, I have read that too, where RAID 5 can be much slower than RAID 1.

Thanks for all your suggestions reagrding this. My conclusion is that the 2.8gb/min rate is probably the best I'm going to manage.

To confirm this, I've updated the firmware on the MSA2012i to the latest version, as well as the NC382i/t network cards in the HP servers. I have also set all the settings on these cards to their default settings using the HP configuration utility.

Having done all this, there was no performance benefit. The only possible alteration I could change is a move to jumbo frames, but sadly the aging HP 5308xl switch at the core of my network doesn't support this.

[teiva-boy]

Speed tapering during a file copy is due to the data being on different parts of the platter within the disk(s).  When you create a partition, data is written on the outer edges of the disk and move inwards.  The outer edge is the fastest part of a disk.  

You also have disk fragmentation, disk seek speeds limitations, etc.  This is why high-end SAN's use SSD for cache for frequently used data, or very large cache systems in the multi GB range.  

[Andrew_-_Nebula · Accepted solution]

Hi,

I think that there may be some caching between the data store / reading and the writing.

The caching will get a speed boost early on until the cache fills up, the estimation of how fast the copy is happening will seem very fast as it is writing to cache / memory and not disk, once the cache / memory has been used up the speed may then drop like a stone and the estimation has to drop very quickly and will keep dropping as it cannot achieve that cache rate again.

It will eventually get down around the non-cache rate.

Regards,

Andrew

Nebula Computer Services