Insanely fast write for the first couple of seconds on an HDD

Deoxir · Nov 29, 2017

I am currently using a seagate 5400 rpm HDD from like 7 years ago. Nothing wrong with it, and just as anyone would expect, terrible write speed is what it features. I understand that and I'm okay with that.

However something weird happened. I was watching a bunch of vids consisting of around 3GB. They are stored on partition A on the HDD. Immediately after I'm done watching I cut and pasted the files to partition B on the same HDD, and I was surprised to see a 200MB/s write for the first few seconds of the transfer, before it went all the way back down to around 20MB/s.

I wonder what caused this? Was it because I used those files right before I transferred them? Would love to learn about it. Thanks!

Unolocogringo · Nov 29, 2017

Most Hard drives have between 8MB to 64MB cache.
Drive transfer speeds will be very fast on any drive, until the cache becomes full. After that speeds drop to what the mechanical disk can actually do.

CountMike · Nov 29, 2017

File transport between partitions on same disk is fast because data is not actually moved, only addresses are changed.

RolandJS · Nov 29, 2017

CountMike, I need to research that. If what I move from partition A to partition B is not actually moved but rather only the addresses are changed, then my full image backup strategy is going to have some "holes" in it.

CountMike · Nov 29, 2017

Yes, never back up to same physical disk and preferably on an normally offline disk, used only during backups and retrieval. Even more serious backups should be kept offsite.

RolandJS · Nov 29, 2017

No problem! Thanks for the heads-up

USAFRet · Nov 29, 2017

RolandJS :

1. "backups" on the same drive are not backups at all.
2. A single copy of a file is not a "backup" by any definition of the word.
3. Never, ever "cut and paste". Copy/paste instead. Then, once verified, delete the original.

If you wish to investigate backup procedures, in depth, read here:
http://www.tomshardware.com/forum/id-3383768/backup-situation-home.html

RolandJS · Nov 30, 2017

Here's my personal example of why I wanted to learn more from CountMike:
When I copied my ISO collection from D partition to C partition, after making sure the collection existed on C, I deleted same from D. I made my backups. If CountMike is correct -- my ISO collection is not backed up into C-partition full image, rather such is backed up into the D-partition full image. Based on the previous posts following CM, I think I might have misunderstood CM's post.

USAFRet · Nov 30, 2017

If you have a single copy of a file, that is not a backup. No matter where it lives.

A backup is a second copy, in case something happens to the real copy.

CountMike · Dec 1, 2017

USAFRet :

Specially NOT on same physical disk and different partitions. You cold have hundred copies and if disk dies or get damaged, you loose all of them.
Offline disk(s) in safe place are only real backup. Level of backup exponentially grows with importance of data. According to Murphy's law, probability of loosing something (like data) grows with it's importance.

RolandJS · Dec 1, 2017

+1 CountMike, and, let me add: using external hard-drives for backups and then storing them in a safe place, a fire-resistant safe is just one of many good places, perhaps 1 HD on the premises and the other HD off the premises.

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Insanely fast write for the first couple of seconds on an HDD

Deoxir

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Unolocogringo

Unolocogringo

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CountMike

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RolandJS

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CountMike

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RolandJS

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USAFRet

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RolandJS

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USAFRet

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CountMike

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RolandJS

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