RAID question

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muddy
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Joined: Feb 25 2008

Hi

Am considering the purchase of an external RAID unit to store my video (and maybe for capturing/editing if it's fast enough!).

Will need to purchase new hard drives - does the size of the internal cache on the hard disk make a difference to performance (particularly with RAID 1)?

Usually with a normal single hard drive the larger the cache the better, but I've heard that with RAID it is better to switch off the disk cache or have as small a cache as possible, is that true?

Cheers
Steve 'muddy' Waters

ChrisBitz
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Joined: Jun 8 1999

if it's an external RAID, isn't connection speed going to be paramount, or are you talking E-sata or something?

muddy
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Joined: Feb 25 2008

Yes, eSATA. Of course connection speed should be as fast as possible, though the primary purpose will be storage (and if it turns out not to be able to cope with capture/editing then that will have to stay with the internal drive, no biggie) so some form of redundancy is key.

Cheers
Steve 'muddy' Waters

PaulD
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Joined: Aug 31 2002

Hi
With RAID sets its the controller that needs the cache memory, not so much the individual drives. Since RAID 1 may be controlled in software by the OS/disk-driver, in that case there's no cache involved except in system memory.

As to on-disk cache, this is of most benefit where the stored file size is smaller than the cache memory size - which doesn't apply with video editing.
The best solution is a 4-drive array, in RAID 10 configuration - two RAID 1 mirrored sets used to create a further RAID 0 stripe.

muddy
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Joined: Feb 25 2008
PaulD wrote:
As to on-disk cache, this is of most benefit where the stored file size is smaller than the cache memory size - which doesn't apply with video editing.

Ah yes, hadn't thought of that, thanks Paul.

Quote:
The best solution is a 4-drive array, in RAID 10 configuration - two RAID 1 mirrored sets used to create a further RAID 0 stripe.

I only wish my budget stretched to that...:)

Cheers
Steve 'muddy' Waters

PaulD
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Joined: Aug 31 2002
muddy wrote:
...I only wish my budget stretched to that...:)

Hi
Cheaper now than it has ever been... :)