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Cache Drive in a Raid 0


Josh

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Is it possible to setup some drives in raid 0 and run as my cache drive?  I previously ran 4 320GB drives on my windows machine that was my "Scratch" drive that did all the unrar'ing, paring, etc... and it was really fast fast.  Since i've moved all of that kind of stuff to unraid its been painfully slow running on a single 7200 drive.  SSD drives won't work, need about 1.5TB as my cache.  If possible is it as simple as creating the stripe on the controller and booting up?  I don't care about temps or spin downs.  Just want to know before I bite the bullet and pick up a few more drives

 

thanks

 

Josh

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yes.

 

You need a hardware raid card. many of the cheaper cards are software based.

 

just keep in mind you are doubleing (or tripple with 3 drives) your chance of the drive failing and all data lost.

 

As far as an SSD cache drive, they work fine.. mostely. The only issue I am aware of is the OCZ drives  show up as -128 deg. As long as you dont run the auto shutdown on drive overheat package, thats ok. As far as I could tell, I was geting the full Sata3 speed on it.

 

 

I have also used a mushkin SSD with no issues. lt reported zero deg.

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are the on-board controllers on motherboards hardware or software?

 

Not worried about cache failing, I backup whatever the mover script doesn't move daily

 

I didn't mean SSD drives don't work, I meant I can't afford to add 1.5TB of SSD's as a cache drive, I wish :-)

 

 

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are the on-board controllers on motherboards hardware or software?

 

Depends on how expensive of a motherboard you're using. Here's some general observations that seem to fit. If it's not a motherboard specifically made for server systems ($400+) then it's software based.

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There is more to it than having hardware RAID. You also want a spindown option, and obviously want unRaid to support it. Look at the Areca ARC-1200 cards. PCIe x1 / 2 port card. Supported pretty well by unRaid.  Has spindown option. Supports multi-RAID. I run one as parity in RAID0, and another as a standalone mirrored RAID1 volume. Also used a RAID0 volume as cache but doesn't work very well sharing same disks with parity.

 

I would comment that you are not going to see much speed improvement with a RAID0 cache drive. Your bottlenecks are elsewhere. If you are running apps locally you might be justified.

 

As parity I get a little write boost - up to 46 MB/sec when writing to a 7200 RPM data disk. Also I can upsize my parity volume up to 6T using my 2 3T disks.

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I'm not going after parity speed and my drives never spin down.  Its taking 7-14 minutes to unrar a 10GB file, partly because of my CPU and partly because i'm writing to the disk at the same time the file is un-raring.  I did a test, it took 2 minutes to unrar a 10GB file on the cache drive when nothing was being written to the disk.  However when SABnzbd is downloading its hitting the 7-14 minute range.  I tried both with unrar'ing through sabnzbd and unraring manually

 

To be honest i'm very tempted to build a little 1U machine just to run my services and take unraid back to just storage, its getting hit with more and more traffic.  Even had trouble watching a movie last night.  Had trouble with a workout video this morning that was just SD.  Kept buffering and everytime it was buffereing I went to the server and it was unraring something and sysload was going over 7.0.  Also everytime it unrar's my DL speed cuts in half, once it finishes it jumps back up to max speed

 

load average: 4.36, 5.42, 5.75.  That's on a dual core AMD X2 240.  If I remember correctly is it correct that single core should stay under 1.0, dual core under 2.0, quad core under 4.0, etc... I've got a new processor coming to see if it makes any difference

 

And I didn't have much improvent with two drives in Raid 0, but when you add 4 to the stripe, I noticed a significant jump, didn't matter if I was writing to the disk and unrar'ing at the same time, it was the same speed not matter what.  I tried 5 and 6 drives and all were the same write speed as the 4 drive setup.

 

Note i'm running sickbeard, headphones, sabnzbd, mysql, plex, slimserver

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Should try what sabnzbd themselves suggest, having the incomplete and complete directories on different drives.  Fewer drives, less chance of total loss, and probably will run at the same speed or better then a 4 disk RAID 0

 

I am using very old and very used 400gb SATA drives for the incomplete and complete disks and unrar of 12gb usually takes under 3 minutes and that is even while downloading something else at 50mb/s.

 

Also, I am running this inside of ESXi with a single CPU and 1GB of RAM (single core off of a e5530 2.4ghz processor).  Load average is rarely above 1.5. 

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