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Hard Disk Procedures and Operation

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December 12, 2010 2:43:03 PM

I would like to ask some quick questions about HDDs.

-What's the difference between quick and full format? I've been told that full formatting is nothing more than a quick format with a full surface scan performed as it goes. So you can instead quick format and do an error scan with HDtune. Is this information Accurate?

-Allocation Unit. Is this something like block size? So does that mean that setting smaller sizes will possible save you space but bigger files get chopped into smaller chunks and this degrades performance? Am i getting this right?

So for example if you set an 8192 byte allocation, that should mean that any file smaller than 8k will still have a size in disk of 8kn while others are divided into 8kb chunks?

Should there be need for a specific setting here, or the default should do?

-What is the formatting procedure dependent upon? I mean the time of the operation? Drive speeds mostly or system resources? Also can i format more than 1 drive at the same time? What happens if the PC shuts down for some reason during formatting? Will the drive get physically damaged?

-And Finally MBR bs GPT? I know GPT is for large disks for itanium based servers, but i just got 4 2TB Samsung and I'm wondering if GPT could be preferable?

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a c 415 G Storage
December 12, 2010 5:16:26 PM

Quick vs. Full format - your understanding is basically correct. The advantage of doing a full format is that any bad sectors are automatically placed into a bad block table so that NTFS won't try to use them. But the drive itself does the same thing at a lower level so it's not a relevant as it once was.

Allocation Units - typically called "cluster size" for NTFS. Again, your understanding is correct. The default 4K size is a good tradeoff for most people. The advantage of smaller cluster sizes is less wasted space due to not using up the entire allocation unit (a bigger problem on a drive with lots of small files). The advantage of larger cluster sizes is less file system overhead for tracking all the clusters as well as reduced file fragmentation. My rule of thumb is to use the default cluster size unless the drive will contain mostly very large files (databases, for example) in which case I use the largest (64KByte) cluster size.

For a full format, the time is dependent on the speed of the drive and it's connection. The faster the drive/connection, the faster the format. USB 2.0 means VERY slow formats on large drives, but even a SATA 300Mbit/sec connection to a hard drive still means several-hour formats for larger (TB) drives (the hard drive itself is a lot slower than the throughput of it's SATA connection). There won't be any physical damage to the drive if the system shuts down during formatting, but it means you should start the format over again from the beginning.

Use MBR partitions for 2TB or smaller drives. The sole reason to use GPT partitions is that they must be used on a drive larger than 2TB. If, for example, you create an 8TB RAID volume out of multiple 2TB drives, you'll need to use GPT partitions. The biggest issue with GPT partitions is that most systems can't boot from them, but that doesn't stop you from using them for data drives.
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December 12, 2010 5:42:16 PM

I see, thank you for getting back to me with detailed answers to my questions.

-Think is that i just formatted my 2TB (on sata2 port) and it took more than 10 hours! I started the procedure this morning at 11, and it finished a few minutes ago at 9:30.

If it's just error scanning that it is performing why is it taking so long? The HDtune error scan option takes almost half as much. It completed a full error scan in 5 hours and 3 minutes.

So it's cool if i just do a quick format followed with an HDtune error scan to ensure my drive doesnt have any bad sectors?

-As for the allocation i guess it was as i thought it should. So for these drives hosting large data, and not program installation and small files, it should be preferable to use 64KB rather than the default? Will this achieve any noticeable difference in file management moving files here and there and accessing them?

-So if i use each disk separate the MBR would suffice, but if i get them on a RAID 0 thus create a whole entity with 8TB space i would need GPT.

MBR it is!

-And a couple of small additional questions.

What is the drive filled with, after the initial format? I notice a total of 157mb or so, on the 2TB drive? Is this comprised with MFT and other information? Is there something to tweak on DATA drives? I remember when i was using diskeeper it allowed you to set file size for MFT and a few other tweaks.
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a c 415 G Storage
December 12, 2010 11:27:21 PM

> If it's just error scanning that it is performing why is it taking so long?

It takes a long time because 2TB is a LOT of data. It's two MILLION megabytes. If the system writes to every sector and then reads the contents back again, then there's 4TB's worth of data being moved around and at 10 hours that works out to about 110MBytes/sec - a very good average transfer rate for the whole drive.


> The HDtune error scan option takes almost half as much. It completed a full error scan in 5 hours and 3 minutes.

I don't use HDTune and so I'm just blindly guessing here - but I suspect that when it does an "error scan" it just reads every block to ensure that the data can be read without error. A format writes data and then reads it back again to ensure every sector is fully functional. It can do this because when you format a drive the assumption is that there's nothing in any of the sectors that you need to keep.


> So it's cool if i just do a quick format followed with an HDtune error scan to ensure my drive doesnt have any bad sectors?

If my guess above is correct, then you're not getting as good a check by doing it this way.


> So for these drives hosting large data, and not program installation and small files, it should be preferable to use 64KB rather than the default? Will this achieve any noticeable difference in file management moving files here and there and accessing them?

The only case in which you'd notice a performance difference is if you were creating and deleting a LOT of files very quickly, and even then I doubt it would be significant. In normal operation I wouldn't expect a performance difference unless you compare it to a small cluster-size drive that's badly fragmented.


> What is the drive filled with, after the initial format? I notice a total of 157mb or so, on the 2TB drive?

Yes, this is the MFT, some of the fixed volume information such as volume shadow folders, and the freespace bitmap. There's really nothing to do after formatting the drive other than to go ahead and use it.
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December 13, 2010 1:06:23 PM

Thank You very much, that covers everything!

Oh and one last thing. Where is the drive letter information stored? On the Operating system or the disk itself? For example if i set one disk as F: will it still be F: on a different computer? IS this information stored internally on the drive along with partitioning and filesystem information? And what if the other computer has this letter reserved?
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a c 415 G Storage
December 13, 2010 3:52:15 PM

Windows stores the drive's serial number in the Registry along with the drive letter. If you put a drive on a Windows system that's never seen it before, it will be assigned the next sequential letter that's available no matter what drive letter it might have had when it was attached to a different system.
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December 13, 2010 4:21:50 PM

Thanks man, you have been really helpful.

I appreciate it!
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December 13, 2010 4:22:07 PM

Best answer selected by therock003.
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December 20, 2010 9:01:03 AM

May i expand some questions for RAIDing?

I just created my first RAID yesterday on 2x SSD's.

What's the importance of RAID size? My mobo has a sata 3 and 2 RAID controllers. On SATA 3 the default stripe size is 64k while on SATA 2 it's 128. I left the default of 64 for these 2 SSD's.

BTW each drive was 60.02 but the total RAID array got a 119.91 size. What happened to the .13? Is this left for RAID information?
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