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Best performance config for 2 fast drives and 2 slow drives?

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  • NAS / RAID
  • Configuration
  • Storage
Last response: in Storage
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May 14, 2012 4:41:28 AM

Folks, wanting to get some opinions here. I'm building a box to primarily be my home file server. The motherboard (Pentium D, 4GB ram) has 4 SATA ports and an IDE controller. I have available for use 2x250GB Seagate Barracuda IDE drives, 2x1TB WD Caviar Black drives, and 2x1TB Caviar Green drives. I'll be building a CentOS box.

I'm planning to make a RAID1 of the IDE drives, and putting "boot", "root", and swap on them. The SATA drives will be used for "home". I want to use 2TB for capacity and 2TB for redundancy.

At first blush, I thought I'd make a RAID0 from the Blacks, a RAID0 from the Greens, and then RAID1 both arrays together for redundancy. But as I understand it, any RAID configuration will be slowed to the speed of the slowest drives (in this case, the Greens).

In a perfect world, what I'd like to do is have the 2 Blacks actively serving up the files as quickly as possible, and mirroring to the 2 Greens as soon as feasible afterward. In other words, I'd like there to be a "primary" array of drives (for performance), and a "secondary" array (but still be able to keep the system running in case of failure in the primary array). Is there any standard configuration that does this?

(BTW, I realize none of this is "backup": I'm also planning on setting up a nightly RSYNC to my NAS box. :)  )

Greatest appreciation, in advance.

More about : performance config fast drives slow drives

a b G Storage
May 14, 2012 5:57:42 AM

about the only solution would be


RAID 0 with 2x WD Black (Partition with Speed Critical Data)
RAID 0 With 2x WD Green (partition with not so speed critical data)

then you have to backup 4tb of data.

Or

RAID 0 2x 1tb WD Blacks
NAS contains 2x 1tb WD Greens for backup as its not raided to the main machine just means backup takes a little longer (NOTE: being across the network drive speed WILL NOT be the limiting factor)
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May 14, 2012 2:06:43 PM

HugoStiglitz said:
about the only solution would be


RAID 0 with 2x WD Black (Partition with Speed Critical Data)
RAID 0 With 2x WD Green (partition with not so speed critical data)

then you have to backup 4tb of data.

Or

RAID 0 2x 1tb WD Blacks
NAS contains 2x 1tb WD Greens for backup as its not raided to the main machine just means backup takes a little longer (NOTE: being across the network drive speed WILL NOT be the limiting factor)


Hmm, neither of these provide any active redundancy (if either of the Black drives fail, the box goes down).

If there is no way to optimally mix the drives, then I may have to maintain two arrays (RAID1 for the Blacks, RAID1 for the Greens), and mount two different volumes for the data. This would suck, though, as there are multiple users in the house, and having to figure out how to allocate some data as "more important" (put on the Black drives) will be a pain. Or, I may just give up on speed and just make one RAID with all 4 drives (any issue with mixing the drives like that?).
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a c 316 G Storage
May 15, 2012 4:05:01 PM

I have a two-part suggestion.

First, look into "realtime backup" software that monitors for changes in a device and copies the necessary backup data to another device. With this, your writes to the faster devices will not be slowed down by waiting for completion of the corresponding write on the slow devices. The shortcoming is that you increase the read load on the fast devices.

Second, a backup to a drive inside the same case is not a reliable backup. Exploding power supplies, lightning, malware, rain, or a three-year-old banging the machine against the wall could destroy your data and your backup at the same time. Consider external backup, either real-time or daily. Oh, wait - you said that. Sorry.

--------------------------------------------------

One other thought. This is going to be a file server. Your limiting factor will be the network connection, not the drives. So drive speed may actually be a non-issue.
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May 15, 2012 5:43:47 PM

Quote:
One other thought. This is going to be a file server. Your limiting factor will be the network connection, not the drives. So drive speed may actually be a non-issue.


I actually hadn't given this much thought, so I looked into it. You're probably right: with gigabit interfaces, there *might* be a speed advantage for the Black drives, but by the time a RAID is involved, it seems unlikely to matter.

So, I should probably put all 4 SATA drives into one RAID. Whether I go for RAID5, RAID6, or RAID10, that'll be for another discussion. Thanks, WyomingKnot.
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May 15, 2012 5:45:21 PM

Best answer selected by darrenbest.
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