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Copy Time?

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by yosho

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Ok folks, I got a disk tranfer question. I'm being posed with a question from management about why our disk to disk backups take so long.

Here's the scenario, if we perform a disk to disk backup of our files (basically a drag and drop file copy from one drive to the next) it takes us about 1 hr 30 mins to perform. This is on a RAID5 U2W SCSI NT4 Server approximately 10GB worth of data (approx 16,000 files).

Well.. Managment just so happened to speak with some know it all that tells them, "I can copy 10GB on my PC from one disk to the next and it only take me like 10-15 minutes" I'm guessing he's on Win98 and just copying 10Gigs from one hard drive to the next on IDE.

Anyhow now they are wondering why the server takes so long. when this guy's PC can do it faster. What should I be telling mgmt? I know what I should say, but I'd like to get some other opinions from gurus that would know.

Thanks.

2 replies

by shiny_topadm

As you probably know, there can be big difference between theory and practice. A huge difference in comparing "copy times" (apart from hardware differences) is the type of copy and the arrangement (and status) of the data. A "drag & drop" copy is a "logical" process, meaning that the source file (or files) are copied from their logical locations. In the case of an active database, these data could be widely scattered over the disk. Access times will be significantly longer than if the data was physically contiguous (10g from system A isn't really the same as 10g from system B). Backup software that makes a physical copy (sector-to-sector) will not be affected by this difference, BUT may use some compression algorithm that will behave differently depending on the data types (mpeg vs. ASCII text, for example). Some Backup software can be set to verify the new copy after it's written. This can add to the time, but most feel it's worth it for the added security. Hope this helps,
---Will

by yosho

I understand what you mean, I just need to find a way to convey to my mgrs. In other words, layman's terms.. :-)

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