Hard drive questions

[Bret Williams]

They’re supposed to be the exact same drive model. But maybe someone can fill in on whether it really matters.

[Craig Alan]

sorry I meant:

does an increase in cache from say 32 or 64 or 128 mean anything significant when it comes to using 7200rpm drives in raids or as bare drives for backing up projects?

Mac Pro, macbook pro, Imacs (i7); Canon 5D Mark III/70D, Panasonic AG-HPX170/AG-HPX250P, Canon HV40, Sony Z7U/VX2000/PD170; FCP 6 certified; FCP X write professionally for a variety of media; teach video production in L.A.

[Mark Suszko]

The RAID is only going to run as fast as the slowest drive in the stack. Cache size may have a small effect on speed, I’d guess.

[Bret Williams]

To my point earlier, are we talking about the raid replacement drive or the backup drive? I’m pretty sure you need to replace the raid drive with same model. Isn’t that why manufacturers keep selling the old models for more money than the newer better ones?

[John Rofrano]

[Craig Alan] “is a raid 5 best with an odd or even number of drives in enclosure or does it not matter?”

It doesn’t matter as long as you satisfy the requirement that you must have at least 3 drives to start with. After that, the more drives, the better the performance. I have all 4 of the internal drives in my Mac Pro in a RAID 5. When I had just 3 drives i got 230 MB/s Read and 208 MB/s Write. With all 4 drives I get 312 MB/s Read and 271 MB/s Write speeds so that’s a nice boost.

[Craig Alan] “does an increase in cache from say 32 or 64 or 128 mean anything significant when it comes to using 7200rpm drives in raids or as bare drives for backing up projects?”

This question has been asked many times and all of the benchmarks I’ve seen don’t show any significant increase in performance with an increase in cache size. I’m sure under some condition the extra cache may give I/O a boost, (maybe for random access to many small files) but I’m guessing that the huge video files that we deal with will quickly overrun the cache and render it useless. Personally, I don’t think the additional money for the extra cache is worth it.

I agree with Bret. You should replace your RAID drive with an exact model number replacement. Not because of caches but because a different model may have a different power saving policy and the last thing you want is for your new drive to drop out of your RAID array because it behaves differently. I have a spare WD RED NAS drive sitting in a draw just in case one of the ones in my RAID goes belly up and they don’t make that model anymore. While you can use any drive of the same capacity, you will have less headaches by using the same model drives.

~jr

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