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Using Flash Disk as Temporary Storage


nant15

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I'm quite sure i'm not the only one who leave my pc overnight to download files. We all know that HDD have a limited up time in HOURS - leaving the Pc on every day just to download at (sometimes) 10-20KB/s is slowly killing your own HDDs while you just got about 70-100MB of data per hour :S . Why don't we use something cheaper???

It would be better if there is an option in uTorrent to temporary store pieces in a selected drive/folder - so that you could just use an old 128MB usb 1.1 USB Flash disk or 64MB SD Card that you're going to throw it away sometime as the temporary storage and configure the power options in control panel to spin down your harddisk after 3 minutes of inactivity. When those drives are full - uTorrent will just move them to the real downloading files - which will spin up the HDD (handled by windows) - when the moving process is complete and temporary storage is wiped out your HDD will wait for 3 minutes and spin down again - Clever huh? :D

Benefit:

- Save HDD lifespan and power consumption (upto 800ma per HDD!)

- You can utilize your old/unsed HDD or flash drive as temporary space for downloading and keep your every day use HDD safe.

- Flash disk has almost 0 seek time - fragmentation is not a problem very suitable to store pieces data.

- Or if you're crazy enough - use Ram Drive as storage (but a power outage would kill all your downloaded data)

Cons:

- Flash disk also has limited life span of 1 Million writes - has to trade this off with lifespan of HDD

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Actually, it's better to leave your hard disk spinning all the time instead of letting it spin up and down. ;)

Why ? I want to know more about it :D cuz currently i have 3 HDD and let all of them spin down after 3 minutes but only when i'm going to leave it for download and i set utorrent to use the 3rd one (its an old school 15GB) for storing download since I though i might save some life span of the other 2... :S

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I think spinning down and then spinning back up is more wear and tear for the hard drive. I don't know for sure though, so take it with a grain of salt ;P

Anyway, you can (as you said on your list of benefits) use an old hard drive to do such kinds of things. Use µTorrent to download your files onto the old hard disk, then move it over to your new one(s) when the file(s) complete(s). I doubt that using flash drives as temporary storage is actually useful, since you still have to write to disk every so often (when they fill up). In that case, you might as well set your diskio.write_queue_size to your desired size (assuming you have the necessary amount of RAM) and use the memory as your temporary storage. Memory is even faster (since it doesn't have the limitations of imposed by USB) and cheaper. Plus, I don't think it wears and tears as easily as the flash drives =P

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I agree that you could just use the old HDD to store the downloads and move them later on when they are completed (actually it is what i am doing). As i have mentioned - for the case that you downloading at 10-20KB/s - the data is only 70MB/hour and i don't think that it is worth spinning HDD for an hour just to write 20000 byte of data every second (didn't take how windows handle the disk write into account which might be more efficient). Why don't we just store these small pieces of data on somewhere else temporary, spin up the disk about once every hour (for 64MB Flash disk) and write them all at once then the drive timeout and spin down - that's what i'm trying to say :D

Actually this idea is from the Samsung Hybrid HDD where it has 128MB NAND flash for write cache - small writes to the disk could temporary store onto this buffer and let the Hdd spin down to conserve power. I think the disk usage scenario of utorrent (again: when downloading at 10-20KB/s) is very suitable for this technique and that's why i proposed it ;)

write_queue_size might be a possible solution, but it is not a good one as it is stored in RAM...imagine that you have to wait an hour to get 70MB of data will you store it to somewhere that it could lost anytime ??? :S

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It's the same with Haddrives as it is with Neon tubes, engines and many more things in every day's life

They age faster the more frequently you switch them off and on...imagine harddrives in professional servers...they run 24/7 for 5-10 years

You can buffer data in RAM (diskio.write_queue_size) but keep the drives spun up

-DG

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an example:

When you are going to start riding a bike, it's heavy and slow but when you gain

speed you can really easy pedal.

It takes more power to start + when the disc's in the HDD spins it doesn't move up and down,

it stays still and spin and creates an airflow which also help the disc's to stay still and

so that the read header doesn't bump into the disc's.

As Ultima said, to start and stop and HDD causes wear and tear

+ the risk that the reader header might bump into the disc's.

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Either spinning down or leaving it on realy doesn't make a big difference.

Leaving a drive on wears the bearings and lubricant. Spinning a drive down wears the head and platters (since they are in contact until the platters have sufficient rotational velocity to create the cushion of air the head rides on).

Servers leave their drives spinning for years at a time without problem. Home users everywhere have their drives spin down after 3 minutes of inactivity without problem. Neither is particulary wearing on the drive, and it should last for 5+ years if you don't abuse the thing.

(though if you put a gun to my head I'd probably say leave them spinning since I'd much rather wear bearings than the head...)

JigPu

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It could just be me (though my luck usually sucks :D), but between me and my friends (10 drives, 3 manufactures, average age of 5 years) I have yet to see a drive die without reason. Actually, I've never seen a drive die at all, even when I tortured my poor 3GB one by pressing on its lid while running (it certianly dosen't work very well anymore -- but I can still get the data off of it without problem)

JigPu

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Another large problem that I can see with using flash memory as your "cache" is data throughput. Most flash disks today have a maximum write speed of 24MB/s (sequential) while average SATA drives go anywhere from 30-50MB/s (sequential). While it is true that downloading should never require a speed that fast, if other applications are accessing the disk as well, the disk bandwidth available for your downloads is significantly decreased. This effect is almost zero with flash memory (no moving parts to go from one position to the other), but is still present.

On a different subject, some specific RAM disks won't lose data even if you turn your computer off anymore in the future:

http://www.pcworld.com/news/article/0,aid,121105,00.asp

The iRAM uses the 3.3V standby power that comes from your PCI slots anytime your power supply is plugged in and on to keep the RAM alive, and a battery to retain data even after your power supply is turned off or unplugged.

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The problem still exists that flash memory in its current state is slower than sequential hard drive read/write access. On random access, it does a lot better, but maximum throughput is luch lower. The only exception I've seen so far is the dual channel USB flash drives that OCZ is making. Those top out at 48MB/s on sequential reads, which is in the throughput range of SATA drives.

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