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Is system operational when rebuilding RAID5 drive?

I have SQL7 running on NT4 server on Compaq Proliant server.
There are 5 disks in RAID5 logical drive.
One disk failed.
I replaced the failed disk and choose to automatically recover at boot up.
Q#1. Can I use the system when it is rebuilding the drive?
Q#2. Does the disk firmware version matter for member disk to successfully build a RAID5 drive?
Q#3. Will it cause corrupted database if users do transactions while it is rebuilding the logical drive?
Thanks a lot.
4 Solutions
Chris MangusDatabase AdministratorCommented:
Yes, you can use the system while the drive is rebuilding.  We do it frequently.  You won't end up with a corrupt database.
It is highly not recommended to do any large amount of activity while rebuilding an array. It is already a slow process and additional I/O activity will slow it down CONSIDERABLY.
That said, 1) yes, you can use the system while rebuilding the array, 2) the disk firmware version should not matter. It can even be a different manufaturer, and 3) it should not cause corruption, but in light of SQL Server being very highly disk I/O intensive, I would use it during rebuild only if it is absolutely, positively, undoubtedly, without reservation, utterly, entirely, without exception, the very, very, VERY last resort.
Chris MangusDatabase AdministratorCommented:
We do it as our systems are 24/7 and we don't have failover hardware.

The heavily used systems do slow down.  Lesser used systems generally don't see the effects.
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1. Assuming that the computer Raid Controller is rebuilding as we speak, you can continue to use the system as long as you realize the risk. With a disk in rebuild state you no longer have redundancy that RAID provided in first place.
2. Firmware doesn't affect the rebuild process, as long as the drive is operational and the raid controller sees it as a viable drive it will rebuild fine.
3. I can't state this enough, until the rebuild is done you have no safe zone. If a second drive fails you are screwed. That being said you can continue to use the system normally while the rebuild is happening, any DB transactions won't be corrupted due to the rebuild.

My advice - boot into the raid controller's BIOS and make sure the rebuild is happening. I'm not familiar with Compaq at all so I can't tell you how to access it (on Dell it's usually ctrl + A or something similar). As long as you rebuild process is happening there's not much else you can do but cross your fingers until it's done.
What controllers do you have? I think I'll change. You could take a vacation if you tried to run SQL Server last time I had to rebuild an array.
My question was directed to cmangus.
Chris MangusDatabase AdministratorCommented:
Our main boxes are HP ProLiant ML570 G3.  Whatever comes in those are what we have.  I don't spec hardware, my network team does that.
richtreeAuthor Commented:
Thank you so much for your quick response.

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