How to expand RAID cards (various posts read) ? - Page 3 - Overclock.net

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post #21 of 42 Old 01-09-2011, 03:16 AM - Thread Starter
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Thank you for all these details biggrin.gif

Btw : initially i opted to RAID6 to fight against UBER smile.gif ...

But, now, many articles advice better RAID level... (like RAID-Z3 ?)

Your advices ?

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post #22 of 42 Old 01-10-2011, 03:04 PM
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With parity RAID levels, there are the following factors to consider:

1) the number of drives in the array,
2) the size of each drive, which in turn determines
3) the size of the rebuild window, therefore the size of the period of vulnerability to complete array failure

In the case of RAID 5 for example, many people say they won't go beyond six or seven drives before they start thinking about RAID 6, or at least RAID 5 + hot spare. But, what size drives are they talking about? 100GB? 250GB? 500GB?

What happens when you get to using 1TB drives, or 2TB drives? The rebuild times are far longer, so while the chance of a drive failing is probably the same, regardless of the capacity of the drive, the opportunity for another drive to fail during the (now lengthened) rebuild period is far greater.

Additionally, while increased areal density will result in faster writes (and therefore shorten the rebuild time), that same increased areal density results in the chance of a URE being noticeably higher.

OK, fine so we use RAID 6. Again the focus here is being able to use arrays with larger numbers of drives, because the chance of three drives failing (electrically or mechanically) during operation is far smaller. But what about UREs? We're now seeing 3TB drives on the market and 4TB will be here by the end of 2011. We may see 6TB by the end of 2014.

I think things like triple parity (RAID-Z3 for example) will help but more importantly, the kind of data checksumming which ZFS uses will prove to be far more valuable, and other filesystems will have to employ such mechanisms if they are to remain of use to those of us with huge storage requirements.

Of course, in the mean time, RAID scrubbing will help to mitigate some of the corruption issues.
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post #23 of 42 Old 01-11-2011, 02:42 AM - Thread Starter
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Thank you very much to make me think about checksum instead RAID level...

I have to admit i was thinking quite only about RAID level...

After reading your post, i was googling around "ZFS end to end checksum" and "Data scrubbing"... that let me afraid how i could "forget" these instructions...

And now, i admit hesitating a lot between all of these solutions...

Thank you smile.gif

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post #24 of 42 Old 01-11-2011, 03:00 PM - Thread Starter
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By the way, i still have hope with such threads talking about PERC / Expander compatibility :

http://forums.overclockers.com.au/showthread.php?t=879827

http://hardforum.com/search.php?searchid=16179255

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post #25 of 42 Old 01-11-2011, 03:38 PM
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I think it's worth pointing out that, although it looks similar, the SAS 5/iR is a completely different card to the PERC 5/i (LSI SAS1064 based rather than Intel IOP333 processor). The 1064 cards work well with expanders - but that doesn't mean you will get a PERC to work also.

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I just learned that <3 is a heart!!! I didn't know. It looked me like a nutsack or something...
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smile.gif it's fine. as long as you fold for OCN it doesn't matter how stupid you are. biggrin.gif
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post #26 of 42 Old 01-11-2011, 04:32 PM - Thread Starter
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Thanks for clearing this biggrin.gif

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post #27 of 42 Old 01-11-2011, 07:11 PM
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Can the SAS 5/iR and SAS 6/iR cards work in JBOD mode?
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post #28 of 42 Old 01-12-2011, 12:44 AM
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yes - as far as I understand it from searching around (I don't own either). But I believe you have to just add a formatted drive to the card for it to show up that way - you can't just add a blank drive then set it up as passthru in the card's bios.

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I just learned that <3 is a heart!!! I didn't know. It looked me like a nutsack or something...
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Quote:
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Nope z, beast is right.
Quote:
Originally Posted by zodac go_quote.gif
I lied about stuff to make me sound more awesome.
Quote:
Originally Posted by csm725 go_quote.gif
smile.gif it's fine. as long as you fold for OCN it doesn't matter how stupid you are. biggrin.gif
Quote:
Originally Posted by zodac go_quote.gif
Thank you.
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post #29 of 42 Old 01-12-2011, 11:53 AM
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Quote:
Originally Posted by the_beast;11980453 
yes - as far as I understand it from searching around (I don't own either). But I believe you have to just add a formatted drive to the card for it to show up that way - you can't just add a blank drive then set it up as passthru in the card's bios.

erm, so hold on a sec. You have to plug the drive into a SATA port, partition it, format it and then connect it to the SAS 6/iR?

I think I'll pass...although if those cards can be flashed to LSI's IT firmware (which I've heard that they can), then they are worth a look.
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post #30 of 42 Old 01-12-2011, 12:07 PM
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maybe not format as well as partition - a brand new drive from the factory should be fine.

A lot of these OEM LSI cards seem to have issue with this kind of thing - my HP card (SC40Ge) wouldn't allow me to delete arrays built on my PERC for example. Not sure if the LSI firmwares are actually that much better, but YMMV...

Quote:
Originally Posted by steevieweevie go_quote.gif
I just learned that <3 is a heart!!! I didn't know. It looked me like a nutsack or something...
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Quote:
Originally Posted by juano go_quote.gif
Nope z, beast is right.
Quote:
Originally Posted by zodac go_quote.gif
I lied about stuff to make me sound more awesome.
Quote:
Originally Posted by csm725 go_quote.gif
smile.gif it's fine. as long as you fold for OCN it doesn't matter how stupid you are. biggrin.gif
Quote:
Originally Posted by zodac go_quote.gif
Thank you.
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