XP NTFS disk compression - reliable?

[Nill Toulme]

Any reason not to let NTFS compress an external HD used for backup?

Nill
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www.toulme.net

[DarkPenguin]

If you're putting photos on it they really won't compress and you make things more interesting for recovery later on.

[Nill Toulme]

Thanks.  It occurred to me belatedly that because 95% of my data consists of already-compressed RAW files, further compression is probably a waste of time...

Nill
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www.toulme.net

[Jonathan Wienke]

Actually, it's not a waste; you'll get another 10% or so file size reduction with RAWs and JPEGs, and it doesn't make file recovery any more difficult. The compression is part of the OS, and is done on individual disk clusters, so the decompression is done before the data is sent to the disk recovery program and therefore file recovery is no more difficult than when working with uncompressed data. I've been using compressed NTFS personally and professionally for over 8 years, and its only downside is slightly higher CPU utilization while writing to the disk.

[jeffreyluce]

I thought this was interesting.... http://www.ntfs.com/ntfs-compressed.htm

Quote from the above link.

The compression algorithms in NTFS are designed to support cluster sizes of up to 4 KB. When the cluster size is greater than 4 KB on an NTFS volume, none of the NTFS compression functions are available.

[Nill Toulme]

Actually, it's not a waste; you'll get another 10% or so file size reduction with RAWs and JPEGs, and it doesn't make file recovery any more difficult. The compression is part of the OS, and is done on individual disk clusters, so the decompression is done before the data is sent to the disk recovery program and therefore file recovery is no more difficult than when working with uncompressed data. I've been using compressed NTFS personally and professionally for over 8 years, and its only downside is slightly higher CPU utilization while writing to the disk.
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Wow, thanks Jonathan.  10% is definitely worthwhile in this situation.  I will give it a try.

Nill
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www.toulme.net

[Nill Toulme]

Heh... when I told it to compress the disk, it started out saying "200 days and 14 hours remaining."  Once it took three minutes to deal with the first outlook.pst file, though, it dropped down to "8 days and 11 hours remaining," so I'm optimistic.  ;-)

Nill
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www.toulme.net

[Nill Toulme]

One more question — is it OK to use a defragmenter, e.g., Perfect Disk or Diskeeper, on a compressed drive?  Well two more — is there any reason to?

Nill
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www.toulme.net

[jani]

One more question — is it OK to use a defragmenter, e.g., Perfect Disk or Diskeeper, on a compressed drive?  Well two more — is there any reason to?

Unless you keep on deleting and adding new files more or less at random on your compressed drive, defragmentation should be superfluous, unless there's something special about compressed drives that make disk utilization even worse than what's usual with NTFS.

But you can check that easily enough by running the Disk Defragmenter.

Basically, defragmentation should only worry you for disks that you need decent performance from. A backup drive hardly fits that description; you won't be accessing it often.

[Nill Toulme]

That makes sense.  Thanks.

Nill
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www.toulme.net

[budjames]

I wouldn't mess with hard drive compression as it's not worth the risk.

How about upgrading your disk drive instead? Drives are cheaper than ever these days.

My Dell Precision workstation has an internal 320 RAID SATA drives. Using firewire800, I have 4 external drives providing another 1,800GB of storage about 800GB of that is used for backups of my image files.

Bud James
North Wales, PA

[Nill Toulme]

This is for a redundant offsite backup drive.  It's a 750GB external that backs up the two 400GB externals that are currently backing up my 1.1TB internal RAID5.

Nill
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www.toulme.net