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Tape drive performance in Comm Vault for VCB backups

Posted on 2010-09-02
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I am having performance issues with my LTO4 tape drives in my Comm Vault environment. I have a Windows VCB proxy server running Windows 2003 server Ent Edition. We are running Comm Vault Simpana 8 as our Ent backup software. There are 2 Emulex HBAs in the proxy server one zoned to the tape drive SAN and the other zoned to the storage SAN. The majority of our ESX environment is ESX v 3.5 so we still need to use VCB. I am seeing on average 1260mb/min when writting to our LTO4 tape drives which if I calculated correctly is roughly 17% of its potential through put. Is anyone else running this configuration and if so what are you seeing for performance? The tape library is an IBM TS3500 with LTO4 tape drives. We have on board encryption running and we are using TKLM as our key management software.
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Question by:bsm4
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by:woolmilkporc
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You should remove this question from the "IBM AIX Unix" zone. It's not related at all to this OS.

wmp


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by:bsm4
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wrong zone
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by:bsm4
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wz
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Gerald Connolly earned 250 total points
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Just to be clear, when you say 1260mb/min you mean 1260MegaBytes/min (common terminology is "B" = Bytes, "b" = bits)?
 LTO-4 is rated as 120MB/s  
1260MB/min = 21MB/sec, which as you say is 17% of the rated speed of the drive.
This kind of reduction probably means that the drive is Shoe-shining* which is something to avoid.
What is the RAIDset that you are reading to write to the tape and is it full of lots of little files or big files?
 
 
*Shoe-Shining - LTO technology streams, as opposed to start stop to maximise tape capacity. That means that once data hits its cache, it winds the tape upto speed and starts writing, until the cache is emptied, at this point it comes to a stop, and rewinds the tape back past the point it finished writing so that when the next data comes along it can wind up to speed before it gets to the end of the original data so that it can start writing as soon as it gets past that point. If the data stream is not coming in fast enough and the drive continually empties the cache then this slow to stop, rewind, speed up forward action, severely slows down the rate that data is written on the tape. IBM drives have several speed steps down from full speed (the HP drives have variable speed) but anything under 30MB/s is likely to cause shoe-shining
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by:smcpartlin
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It sounds like you need to stream more jobs together to help push more data.

You also need to remember the backup server or media server pulls it's data over the LAN from the agent on each server.
How you backup VM's may differ depending on how the agents are setup. In the vm or on the hypervisor.

Make sure to check the LAN and see if you can stream more data jobs together.

Otherwise.  Backup to a new disk target ( that you put in) and then aux copy to your lto4.

If at that time you still get poor performance you need to call Comvault support.
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by:Dr. Klahn
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I've requested that this question be deleted for the following reason:

This question has been classified as abandoned and is closed as part of the Cleanup Program. See the recommendation for more details.
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by:Gerald Connolly
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Lots of valuable advice given

Split points

ID:33611362 Author:connollyg
ID:34793067 Author:smcpartlin
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