Getting the most out of your LTO4

HI there, we are currently suffering poor speed to our LTO4 and direct 2 disk backups.

LTO4 write speed is about 20gig a hour, this is LOW.

I'm currently specing a new server and MSA60. My question is.

 I'm aware more disks the faster the feed to the LTO4, but does the OS or the data need to be on the MSA60 (24 disk external shelf) to get the maximum lto4 tape speed?

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The only time I have seen LTO4 tapes running at full speed was when backup data was being staged to a RAID 5 set on Fibre Channel disks and it was then being sent to the tape via fibre.

Even a SATA disk pack is not adequate. Thankfully though the LTO4 drives can step down in speed so that you do not shoe-shine the drives.

It will also depend on the type of data you are sending as well. If you are backing up many many small files you will have slower speeds.

In summary, backup all data to fast disk that is accessed by your media server then have that media server stage the data to your LTO4 tape drives via the media server.

I hope this helps.
MC2010Author Commented:
Found the solution.

GIven you have enough ram, the data passes from the data source (MSA60 12 x 500 gig 15k scsi disks) through the host memory controller, through to the tape drive. given the msa60 can provide a 50MB/sec stream, the LTO4 will enter stream mode for fast backups.

Given the host has enough IO grunt to pull from the msa60 at 30MB/sec + and push to the LTO4.

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Having the correct memory buffer settings on the Media Server is important however you will never get to 120MB/s LTO4's top speed pulling data from anything below Fibre Channel disk packs.
Thomas RushCommented:
Three other mistakes not to make with LTO-4:

1) Let the tape drive compress the data.   If you do it server-side, you'll probably see significantly slower performance and very high server CPU use (possibly affecting other applications as well).

2) Since compression puts more stress on the disk subsystem (it has to be able to provide more data to the tape drive in order to keep it from getting into a buffer underrun situation).... in some cases, you'll see much less wear-and-tear on both the tape media and  the tape drive if you disable both HW and SW compression.   I don't recommend this unless you can't keep the drive streaming any other way.

3) If you have a need to encrypt the data on tape.. again, let the tape drive use its hardware to perform the encryption... do not encrypt in software, else you'll again see high CPU utilization, a decrease in the speed of data sent to the tape drive, and a loss of compression.
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