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RAID Advice

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September 7, 2011 12:13:50 PM

Hi there,

I need some advice regarding a RAID Card. I am trying to set up a RAID system in my home as a media server and hard drive image server. I have 4 - 3TB (6gb/s) SATA Hard drives whcih I wanted to configure into a RAID 5 solution. I had purchased the Highpoint 2720 which I set up. It failed once and caused a mess... i reset and reloaded a ton of media but I find that it is VERY slow (writing at 8mg/s - 11meg/sec). If I write to the drives, the server is almost unuseable.

I like the idea of RAID 5 because it provides some measure of redundancy but have now starte to think about raid 1-0 (duplicate of 2 drives) but this will reduce my capacity from 9 tb of useable space to 6 tb of useable space (I Know that 6TB is a lot of space but I also have 5 computers in my home that I want to regularly backup on the server as well). I do not know what the speed difference would be although I would assume that RAID10 would be much faster. I need a card that can handle running the media server and also backing up hard drives and will do so at an acceptabe speed (i.e., when writing, the computer should still be useable)

My computer is a Windows 7 box with 4 gb of RAM. The OS is on a spearate drive.

Any advice on a good and reasonably fast card would be appreciated. My budget is about $600.00.

One model that I have considered is the Adaptec 6805. anyone have experience with it?

btw, Highpoint has the worst customer service i have ever dealt with. I will never purchse a product from them again. Please do not recommend any of their cards.

Dave

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a c 415 G Storage
September 7, 2011 5:40:30 PM

The biggest weakness of RAID-5 is its very poor write performance. An intelligent controller with plenty of RAM for write caching can mitigate this to some degree, but if you're writing large volumes of data (like backups, for example) then you're probably still going to have performance issues. Caching can only do so much. RAID 1+0 will be much, much more responsive under heavy write loads.

You should also be aware that an online server in the home makes a questionable choice for backups since, for example, it will likely be stolen along with all of your other computer equipment.
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a b G Storage
September 7, 2011 6:35:05 PM

sminlal said:
The biggest weakness of RAID-5 is its very poor write performance. An intelligent controller with plenty of RAM for write caching can mitigate this to some degree, but if you're writing large volumes of data (like backups, for example) then you're probably still going to have performance issues. Caching can only do so much. RAID 1+0 will be much, much more responsive under heavy write loads.

You should also be aware that an online server in the home makes a questionable choice for backups since, for example, it will likely be stolen along with all of your other computer equipment.



For one thing, I don't recall that card supporting 3TB drives. It supports volumes >2TB, but not 3TB drives. Advanced format drives on that controller could be the source of your problems.



And to correct sminlal, RAID 5 has poor performance when implemented improperly. I use RAID-5 volumes at work for file shares, and they easily manage 80-90MB/sec using Dell PERC raid cards. One thing I need to mention is that the Highpoint 2720 is a budget entry level card. It contains NO cache. This has a huge impact on performance when operating in a RAID level that requires parity calculations (5, 6, etc.). While your performance should be better than 8MB/sec, don't expect stellar performance from a $75 RAID card.

a b G Storage
September 9, 2011 7:05:36 PM

I second that, you get what you pay for.

RAID5 performs well when done well. Is it slower than non-raid on identical hardware? Probably, but that's not the point.

Almost any controller out there will have to have recent firmware in order to support 3TB drives.
September 16, 2011 12:05:28 AM

Hi there,

I got the adaptec 6805 which is at least 3 times faster than the highpoint at RAID 5. It is copying at about 30 meg per sec. I still haven't tried to stream media but expect it to work well. If I find it too slow, I will simply reformat and got to RAID 10

thanks for the help

dave
a b G Storage
September 16, 2011 1:29:35 PM

You should be getting better than 30MB/sec on that card though. What stripe size did you select when you created the array?


September 16, 2011 1:33:58 PM

what speed should i get? the stripe size was set at whatever the default is. I can reformat and start over. what stripe size would you recommend?
September 16, 2011 2:46:41 PM

Good discussion!

I have several raid 5 arrays. Some hold static media like itunes, or movies. One is for backups. Another is for SageTV recording / watching and another for storage of family photos.

Of these uses SageTV and the family photos are best suited for Raid 5. The Raid allows fast reads so I can stream multiple highdef SageTV streams so that is a useful benefit. The redundency of RAID 5 gives me peace for the family photos.

I'm not sure the complexity of RAID 5 is really useful forstoring movies or other kind of static things.... JBOD with compressed backups may be easier for those types of needs.

Just my $0.02.
a b G Storage
September 16, 2011 3:15:50 PM

daveman said:
what speed should i get? the stripe size was set at whatever the default is. I can reformat and start over. what stripe size would you recommend?




For large files like movies, DVR streams, etc, i'd use a 128k stripe size. For lots and lots of smaller files like photos, documents, etc, a smaller size like 32k or 64k would be optimal. Unless those drives are just really slow drives, 30MB/sec just seems slow to me. What's the make/model of the drives?



a b G Storage
September 16, 2011 3:20:09 PM

mbahr said:
Good discussion!

I'm not sure the complexity of RAID 5 is really useful forstoring movies or other kind of static things.... JBOD with compressed backups may be easier for those types of needs.

Just my $0.02.




RAID 5 isn't as complex as everyone assumes it is. It's very effective and allows you to get the most out of your disk space, compared to mirroring. With a RAID 5, you have inherent redundancy without the need to do backups to separate media like a JBOD. Mirroring doesn't make the most out of your disks' space, since it is a 1:1 backup system. Compressed backups wouldn't do any good for a collection of music or movies, as they're already compressed formats to begin with. You'd get better backup speed to just turn off compression, if your're backing up highly compressed files like that.
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