RAID: Hardware or Software?


W

Wendell III

Hi all,

It was recently pointed out to me that there may be some negative
points in buying something like a 3Ware RAID card, versus using a
software array via Linux -- namely that the card could die (or die and
be obsoleted, with no replacement card available), leaving the array
totally unusable. Is this actually true? Are there any "standard" to
these kinds of arrays that would allow me to migrate to another card or
migrate to software, without losing all my data? What's the skinny on
this, generally speaking?

Cheers,
-Wendell
 
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A

Arno Wagner

Previously Wendell III said:
It was recently pointed out to me that there may be some negative
points in buying something like a 3Ware RAID card, versus using a
software array via Linux -- namely that the card could die (or die and
be obsoleted, with no replacement card available), leaving the array
totally unusable. Is this actually true?

Well, you can get a new card from the same vendor and hope. In order
to be sure you need to have a backup card handy, i.e. you need to buy
two RAID cards. And if one does, you need to buy two new cards and
transfer your RAID.
Are there any "standard" to
these kinds of arrays that would allow me to migrate to another card or
migrate to software, without losing all my data?

No. There is some general RAID recovery software, but it requires
you to hook up the disks to normal controllers and costs money.
After all the vendors do _not_ want you to be able to switch
brands!
What's the skinny on this, generally speaking?

My approach is to first ask myself what I catually want hardware
RAID for: Speed and hot-swap. Speed is not that much worse with
software RAID, as long as you have a fast machine and not too
may disks in your array. But even with an 8 disk array I get the
more speed as a single disk would have, which for me is ehough.
On the otehr hand I have a pice of expensive trash, namely an
ADAPTEC 8 disk SATA RAid controller that is actually slower
than software RAID and needs forever for a resync. And has crappy,
unusable admin tools. And is missing SMART support.

Since I don't need hot-swap, hardware RAID is not really an
option for me. On the other hand software RAID has a lot of
flexibility that hardware RAID does not give you. And it allows
you full control on whatever you want to do.

So I think in the end the real question is whether there are
any compelling reasons to use hardware RAID and if not, do
it in software. Even redundant booting is not an issue anymore,
Grub will boot from both disks in a RAID1 set if configured
correctly.

Arno
 

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