On 05/22/2011 11:41 AM, Stan Hoeppner wrote:
On 5/21/2011 6:54 AM, Ed W wrote:
In fact if you go back to my question, the *entire* point is that I
don't want the choice of card to be a point of failure, ie it's my
specific point to purchase a card such that it can be swapped out for
near any other card in the event of failure.
You're given about 3 or 4 conflicting requirement now WRT your 'perfect'
HBA.
What HBAs are you currently using? How many of your stated requirements
over the past few days do your current HBAs fulfill?
Do you have a tape or D2D backup system in place?
There is no guarantee that you can swap one dead HBA for another brand
with a different chipset on board and have it work without issue. If
you are that concerned you need to buy two identical cheap HBAs so you
have a spare. But wait! You must have hardware write cache for md RAID
as well. But if you do that, you're locked into that vendor's cards.
And on, and on...
I've never seen nor heard of a real SA in a business environment
vacillate like this over a simple RAID/HBA acquisition, as if the
company's entire 1st quarter net profit was being wrapped up in this HBA
purchase. And I've never head of an SA being concerned about cable
tripping of all damn things taking down a server.
Something in this whole thread just doesn't jibe...
The amount of money that his time has cost discussing this & thinking
about it, is most likely already noticeably more then the cost of a
mid-range RAID card.
My approach (and i have my own small company):
- use HW RAID on the system disks (RAID5) (and have a spare controller
of same type ready)
- use MD RAID on big storage with cheap disks (and have spare disks
lying ready)
- have a nightly automated backup to different system, with versioning
and ability to recover state of half year ago
That other system is in different building.
As i do not upgrade the servers that often, this ensures:
- i do not need to spend a long time on getting the system back up, if a
system disk goes bye-bye
- no need to think long on how grub/lilo was supposed to be working for
multiple disks
- no need to remember to re-install bootloader on all related disks (so
i safe-guard against my own mistakes. Takes some money, yes, but i am
willing to pay that part of insurance quit willingly. I am aware i make
mistakes, especially when time pressure is high)
- backup in place for the usual stupid mistaken deletes.
yes, i keep spare controllers. Do i need them? not really... so far i
have had only 1 raid card die on me... in 10+ years i am using them.
I've had many disks go to bit hell, and some mobo. Not raid cards though.
My main issues with this discussion, is that it assumes:
- no time pressure when the shit hits the fan
- the system maintainer does not make mistakes
Both of them fail in real-life, especially with the small businesses
where this discussion is relevant for cost reasons. Thus my stated
feeling of "penny wise, pound foolish". Murphy being what it is, things
usually fail when you need to have your attention on something else.
That means there is great opportunity at such a time to make mistakes.
Thus the setup of such systems needs to take the human aspect into
account. As far as i can see the setup he is defining is simply too
complex for the situation.
I've had things fail on me when i needed to leave in 2 hour, as i had a
flight to catch. I also needed that server to be running...
Cheers,
Rudy
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