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MSL 5000 Too Slowwww

jonathan green_1
Occasional Visitor

MSL 5000 Too Slowwww

We currently have a MSL 5026S2 tape library connected to an adaptec 39320D Scsi Card. The tape library is configured with 2x 160/320SDLT drives in a 2 drive one host config.
Terminated as the manual

The Scsi card resides in a Brand new HP/Compaq DL380 with 1 GB of Ram and a 2.8ghz proc.

We have carried out the following tests.

Backup of a local system volume on to each drive separately 600mb/m, when we try and schedule a job to both tapes at the same time the throughput drops below 250mb/m per job.

When we backup other servers across the LAN we get upto 600mb/m on and individual drive, but again when we backup using both drives we only get around 250mb/m each...

This is the system we are currently testing, we have actually got two of these units (MSL)and two servers (DL380) to ultimately backup 2.6TB of data.

Is there any way of combining them / configuring them to backup at a faster rate?

We are happy to schedule four jobs to run conquently, but we need the through-put...


Regards

9 REPLIES
Vincent Farrugia
Honored Contributor

Re: MSL 5000 Too Slowwww

Hello,

Most probably, you daisy-chained your SDLT drives to 1 SCSI controller.

That is a big no-no.

In order to get the maximum out of your SDLT drives, you have to put them on seperate SCSI buses.

600Mb/min = 10Mb/s. Your SDLT 160/320 is capable of 16Mb/s native speed, so even that is a bit slow.

When you start two backups at the same time, though, you would hog the bus, that is why the throughtput suffers dramatically.

Please try to connect the drives to seperate SCSI buses.

HTH,
Vince
Tape Drives RULE!!!
Peter Mattei
Honored Contributor

Re: MSL 5000 Too Slowwww

I fully agree with Vince.
Further, if you do not satisfy the speed needs of your tape drive it will go into shoe shine mode. This will 1. slow down backup performance 2. kill your drive and 3. wear your catrtridges.
I suggest you download and use PAT (Performance Assessment Tool) It will show you where your bottlenecks are!
http://search.hp.com/gwuseng/redirect.html?url=http%3A//h20015.www2.hp.com/en/softwareDownloadIndex.jhtml%3Flc%3Den%26softitem%3Dco557en%26sw_lang%3Den&qt=performance+assessment+tool&hit=1

Cheers
Peter
I love storage
Peter Mattei
Honored Contributor

Re: MSL 5000 Too Slowwww

Vladimir Vybiral
Valued Contributor

Re: MSL 5000 Too Slowwww

Yes, shoeshine is bad. Be prepared that once You put the drives onto separate controllers, the LAN could be a bottleneck if it is not 1GBit - or, if it is, the bottleneck could be in the processing power or PCI bus - put SCSI ctrls to different PCI buses. If the results for PAT seem not valid, try to use Backup to null device (depending on the backup SW You are using it may be not possible) to test if the bottleneck is outside of the PCI-SCSI-tapelib path...
When speaking, Your words should sound better than Your silence - Arabic proverb
Glenn Weavind_1
Frequent Advisor

Re: MSL 5000 Too Slowwww

PMFJI, but it's unlikely that the SCSI bus to the SDLT drives is the bottleneck: these tape drives have wide Ultra-2 interfaces, capable of 80M bytes/s in synchronous mode, with decent buffers on the drives. I suspect Vladimir has put his finger on the problem: the bottleneck is the LAN. People often forget that 100Mbps f/d Eth only transfers data at 12MB/s, and the native rate for SDLT 160 is 16MB/s - with reasonable compression the drive absorbs data at 25MB/s. Only Gigabit Eth can possibly deliver data at this sort of rate: you'll probably need to add a second processor (however fast they are) because the GigEth NIC will be generating hardware interrupts so quickly in this environment that most of one CPU will be spent just servicing hard IRQs (although they will be spread across both CPUs if installed correctly). I still wouldn't attempt to put more than two SDLT drives onto one bus though...
Peter Mattei
Honored Contributor

Re: MSL 5000 Too Slowwww

FYI, PAt will also show you that, because it you can include the LAN into the analysis.
But true, 1x 100bt will give you max. 10MB/sec.
As you can read Jonathan also sees the drop in performance with local data! So the SCSI path looks like the problem. Neverteless it is supportde to dasychain 2 SDLT to one SCSI.
I would also check your SCSI cables, terminator and the total cable length.
Peter
I love storage
Vincent Farrugia
Honored Contributor

Re: MSL 5000 Too Slowwww

Hello,

Indeed, Peter.

However, if it is supported, it does NOT mean that it works fine for both tape drives at the same time. You can have 15 SDLT tape drives in 1 SCSI bus in theory. But would it work? If you backup 1 at a time, then yes. If more than 1 are performnig backups or restoring, then no, that would be too much for the bus.

HTH,
Vince
Tape Drives RULE!!!
Dave Dewar
Trusted Contributor

Re: MSL 5000 Too Slowwww

Hi,

I would agree that you have a local bandwith issue and a network bandwidth issue. Any network backup/restore will be limited to a max of 10MB/s as other posters have said. This will not keep one SLDT drive well fed, let alone two.
Also, I would recommend one drive per scsi controller if you can. A dual controller would be ok here as the bottleneck will not be the PCI bus but rather the SCSI bus.
Although the scsi interface on the drive is capable of 80MB/s synchronous, there will still be a significant overhead of non data phase SCSI commands, which will use up available bus bandwidth.

Also, operating at low transfer rate modes that will cause the drive to streamfail and reposition will not kill your drive as other posters have mentioned. It is not desirable from a performance standpoint and will create more media wear and is conesqeuently not good practice from a reliability standpoint, but your drive will not die because of it :-)

Cheers,

Dave Dewar.
Peter Mattei
Honored Contributor

Re: MSL 5000 Too Slowwww

It will not be a sudden death, but we have seen this issue with lots of DLT8000's in the past. Due to mechanical stress they fail far before the expected age where else in streaming environments they run for couple of years!
Peter
I love storage