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Should I be using raid 3 or 5?

Last response: in Storage
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November 14, 2009 5:30:37 PM

I'm going to be implementing a raid setup in my computer for heavy video editing/storage. I need about 3-5 TB's, around thereish. Anyway, ive read good and bad about both, mainly that raid 5 is slower than raid 3, but in raid 3 if the HD fails that has some type of index on it, then you lose all of your data.

Can someone shed some light onto this for me? I'd be using my built in GIGABYTE GA-EP45-UD3P raid controller.

Suggestions?

Hmm, I've also just read about raid 10 - any suggestions about that?

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a c 415 G Storage
November 14, 2009 7:12:36 PM

RAID 3 is bit-striped RAID that is very uncommon - it requires a very special controller and often uses special disks that are synchronized to spin in unison.

RAID 5 has poor write performance, and may not be a good solution for a video editing application which from the sounds of it would often do bulk write operations.

Your best bet for performance, assuming you need redundancy, is RAID 1 or RAID 0+1 - but be prepared to pay twice as much for storage (you need 10TB of disk capacity to hold 5TB of data).

RAID is not for the faint of heart - be prepared to spend time testing how your system responds to drive failures so you know what to do BEFORE you load critical data onto it.

You're going to need to back all that data up to external media - make sure you have that requirement covered before getting in too deep with RAID.
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November 14, 2009 7:20:57 PM

Hmm.. would you still find it worth doing myself in my own computer vs. some external 6TB solution that seems to run for 1,200 or more $? Seems a lot more cost effective to try and do it myself.
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a b G Storage
November 14, 2009 7:40:44 PM

I'd go for RAID 10, personally. If you need 3-5 TB, you could go with 4 2TB drives in RAID 10, giving 4TB usable space with full redundancy. It would run around $1200 for 7200rpm drives like the new Seagate Barracuda XT or the WD Caviar Black 2TB, or around $600-$800 for slower drives like the Seagate Barracuda LP 2TB or the WD Caviar Green 2tb.
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November 14, 2009 8:04:12 PM

cjl said:
I'd go for RAID 10, personally. If you need 3-5 TB, you could go with 4 2TB drives in RAID 10, giving 4TB usable space with full redundancy. It would run around $1200 for 7200rpm drives like the new Seagate Barracuda XT or the WD Caviar Black 2TB, or around $600-$800 for slower drives like the Seagate Barracuda LP 2TB or the WD Caviar Green 2tb.


Yeah that has been seeming like an option. Oye, seems like I can't get away with a cheap solution here. Maybe I would be better off getting a 2 TB external, and a TB internal, backing up ultra-critical stuff to the external and keeping the thing shutoff most of the time lol.
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a c 127 G Storage
November 14, 2009 9:56:25 PM

RAID3 is indeed special, but it does exist. For example on FreeBSD, the geom_raid3 driver has benefits over RAID5 because it has no 2-phase writes, where data first has to be read in order to be written. In other words, for every I/O request, all disks in the RAID3-array are involved. This is the exact opposite from RAID5, where ideally only one disk handles a single I/O request, and others are free to simultaneously handle different I/O requests.

In the FreeBSD implementation the RAID3 implementation is sector-level, where the sector size of the array volume will increase beyond the usual 512 bytes. For me this kind of stuff is very interesting, but i can imagine no user would want RAID3 these days. Especially now that ZFS has variable stripe sizes to achieve a similar effect.

To the OP: i would focus on RAID 0+1 instead of RAID3 or RAID5. You can also choose RAID0 without redundancy, and use a 1:1 backup instead. This costs the same disk space as RAID 0+1, and you'll lose the uptime advantage of RAID 0+1, but you gain additional data security protection, for example against filesystem corruption, accidental deletions and virusses, etc.
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a c 176 G Storage
November 14, 2009 10:27:00 PM

sminlal had some good points.

What is your objective in using raid?

The value of raid-1 and it's variants like raid-5 for protecting data is that you can recover from a hard drive failure quickly.
It is for servers that can't afford any down time.
Recovery from a hard drive failure is just moments.
Fortunately hard drives do not fail often.
Mean time to failure is claimed to be on the order of 1,000,000 hours.(100 years)
Raid-1 does not protect you from other types of losses such as viruses,
software errors,raid controller failure, operator error, or fire...etc.
For that, you need EXTERNAL backup.
If you have external backup, and can afford some recovery time, then you don't need raid-1.

If you are looking for performance, then a striped array can be of a benefit, but only if you are doing sequential operations.
If you have only two drives, then separating the input drive from the output on different drives is simpler, and more effective. If you have four or more drives, then have two striped arrays of two drives each, one for input, and one for output.

If you expect to get the maximum theoretical performance, be prepared to use a pricey add on card, not motherboard raid.

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November 14, 2009 10:38:44 PM

you should consider a raid card, you should have increase performance and lower CPU workload.

a good raid card will be a lot better than the onboard raid controller...
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