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HP MSL 2024 SCSI 1840 drive throughput

 
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Frequent Advisor

HP MSL 2024 SCSI 1840 drive throughput

Hi All,

I am using MSL2024 SCSI 1840 drive to backup 6-7 TB data from SAN every friday. My everage backup throughput is 6.2GB/min to 6.4GB/min via 4 Gigabit NICs using arcserver backup software with multiplexing option.

Hardware commpression is enabled. I notice that each LT04 only hold around 1.2 TB, that means I am archiving compression ratio 1.5:1 with my current data.

Based on MSL2024 specification, data transfer rate for commpression 2:1 is 864 GB/hour. Which mean I should archive max 648 GB/hour or 10.8 GB/min for compression 1.5:1. am I correct?

Is there anyone here that archive better throughput than me so I can do a comparison?
I and my team tried to find out why we are running at max 6.4 GB/min from SAN with 4 NICs.

We are not going for backup from SAN via FC using VDDK as all vmdk files will be backed up and that is a big amount of data.

Thank you.
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Honored Contributor
Solution

Re: HP MSL 2024 SCSI 1840 drive throughput

if I well remember, the lto 4 have a transfer rate of 120 MB/s native, this should be the max he can write to the tape itself, and the speed is limited by the tecnology and the motor.

you are seeing 6.2 GB/min that is 103 MB/s


now seeing these number that looks apparently good, 103 vs 120, but in fact I do not know where and how you are checking the troughput

apparently if you reack 6,2 GB/min = 103 MB/s with a Compression ration of 1.5 you should be able to reach a troughput of 103*1.5 = 154 MB/s = 9.2 GB/s

I have not very clear how the library is connected, but in order to test if the reduction is comming from the data source of from the target (the msl2024) you can use LTT with the "dev perf" test.
This test will generate data in the host memory and via the scsi bus (or FC bus) will send the data directly to the Drive, showing the effective speed you can reach in your configuration (host, HBA, scsi of fc path and Drive)
I suggest to use a amount of data that run for at least 15 minuts in order to avoid false report due to buffer etc...
If the result reach the expected value (120 MB/s with 1:1 compression or 240 MB/s with 2:1 compression) then the problem is with the data source, or data source path.
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Frequent Advisor

Re: HP MSL 2024 SCSI 1840 drive throughput

Thank you so much for your response with interesting information, Marino.

Could you please give me more details on LTT with "dev perf" test?

9.2 GB/min (not GB/s) is what i'm targeting for.
My current tape lib connected to backup server via SCSI interface.
The currently average throughput is reported from ArcServer backup program. It reports how much data has been backed up, how many files and throughput.

Thanks again.
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Frequent Advisor

Re: HP MSL 2024 SCSI 1840 drive throughput

Hi Ken,

personally, I find this throughput rate very good. I am stuck with 2.5 GB/min from local disk arrays.

If you try to match your total throughput rate with your compression ratio you should have in mind that both are average values while 864 GByte/h is a absolute maximum.

First you loose a bit due to soft write errors, second it might be (and that ist very likely) that the compression ratio of your data is not constant. So it might be that sometimes the date from SAN are coming too fast to write them to tape w/o loss of throuput and sometimes the tape could write more data if even the SAN would deliver it in time.

Hope that helps a bit,

Jerns
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Honored Contributor

Re: HP MSL 2024 SCSI 1840 drive throughput

when you start LTT, and you select one drive, in the upper area of LTT windows, you will see one button that says "dev Perf"
this is what you need to select. In the left panel, then you will have the possibility to select options, here you can choise some parameters, one is the time or the amount of data you want to use for the test.
The test will overwrite your tape, so use a scratch one, if possible a brand new one, or a know good one, as a bad tape can inpact your performance too.

Yes, typo, 154 MB/s = 9.2 GB/M

related to the mesurement, if you got it from ArcServer, then this is mesuring the data source, and it is uncompressed data.
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Frequent Advisor

Re: HP MSL 2024 SCSI 1840 drive throughput

Thank you everyone.

Thank you for introduce me LTT software. I tried HP Tape Assure but it could not detect my drive with lastest firmware.

I will try with LTT and report the result soon.
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Valued Contributor

Re: HP MSL 2024 SCSI 1840 drive throughput

Ken

I have a DL580 G5 connected to an MSL2024 1840 SCSI via a SC11Xe HBA.

Using ARCserve R15 to backup some 10GB files from a local RAID5 partition yields me an average throughput of 5.174GB/min.
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Frequent Advisor

Re: HP MSL 2024 SCSI 1840 drive throughput

Hi CLEB,

5.2 GB/min from local backup is good throughput I think.

In my case, I had to use 4 NICs and backup multiplexing from 4 sources simultaneously to get average of 6.2 GB/min.

Also, throughput is higher when backing up somes big files compared to thousand small files.

Will update after doing testing with LTT.
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Honored Contributor

Re: HP MSL 2024 SCSI 1840 drive throughput

An often overlook tuning parameter is the transfer size your application is using. To hit the maximum transfer rates you have to use at least a 256K transfer size.
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Frequent Advisor

Re: HP MSL 2024 SCSI 1840 drive throughput

Yes, I'm testing with different size at the moment.
I tried from 48, 96, 128, 512 already. unfortunately, average throughput is almost the same. This week full backup will be run with 256.

Arcserve explained that, small size mean software tries to send packet immediately to keep data stream constantly rather up and down.

Let see how it's going with 256, but I guest throughput will remain the same.

Thank you for you suggestion.