Simon Banton wrote:
At 15:43 +0200 14/9/07, Sebastian Walter wrote:
Simon Banton wrote:
No, I haven't. This is 3ware hardware RAID-1 on two disks with a single LVM ext3 / partition - I'm afraid I don't know how
to go about
discovering the chunk size to plug into Ross's calcs.
You can see the chunk size either in the raid's BIOS tool (Alt-3 at startup) or, if installed, in the 3dm CLI (defaults to 64k, I think).
Hmmm, from what I can see in the tw_cli documentation, stripe size (and hence, presumably, chunk size) doesn't apply to RAID 1.
Some cards do, some cards don't. I suppose the idea is by chunking the data in a RAID 1 the logic on the card can be the same between a RAID1 and a RAID10 (just a 2 drive RAID10) and therefore can save R&D money and NVRAM costs due to smaller firmware.
(apologies is the formatting goes awry):
Stripe consists of the logical unit stripe size to be used. The following table illustrates the supported and applicable stripes on unit types and controller models. Stripe size units are in K (kilo bytes).
I'm going to guess that it is not configurable, but 3ware uses 64k chunk size on RAID1 simply for the cost savings mentioned earlier.
It will have 0 performance impact either way.
I'm focused now on swapping the card for a fresh one to see if it makes any difference, as per Ross's suggestion.
Well I should have said try on another identical machine too in case there is something off on this one, and since you have 2 others and time to kill until a different model machine arrives...
-Ross
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