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I know tw_cli can migrate the RAID5 to an added additional disk, but the capacity will not grow until the machine is rebooted. So is it possible to grow a RAID5 array with no downtime? What is a raid controller that supports this? (pick one)

OS is linux.

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closed as off topic by Zoredache, Dave M, Khaled, Wesley, Chris S Apr 26 '12 at 19:45

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A software RAID can do a hot-add. – Zoredache Apr 18 '12 at 22:52
Do note that even if you grow the array online, doing an online filesystem resize is going to be a tad trickier... – Charles Apr 19 '12 at 4:36
Can't ext3 or ext4 do a hot filesystem resize? Thanks! – cat pants Apr 20 '12 at 0:01
up vote 5 down vote accepted

In addition to Zoredache's comment that plenty of software RAID solutions can add capacity without a reboot, let me say: Yes, there are hardware RAID controllers that support the expansion of arrays without a reboot.

For example, the LSI Logic 8308ELP supposedly allows for this. If you're asking for specific product recommendations, I'm afraid we can't help; that's against the rules here.

Rest assured that what you want can be done, but it's a matter of caveat emptor.

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But whether it's done via hardware or software make sure you have an up to date and tested backup before you start. – John Gardeniers Apr 19 '12 at 0:52
I totally understand that hardware recommendations are against the rules, but of course the problem becomes going through the documentation for every RAID card and trying to see if this feature is supported. The result of this task is simply a statement of fact, a response to the question "Can RAID5 be hot expanded with this card?" Therefore, I would submit that compiling a list of cards where this is supported is exactly in line with the spirit and intention of ServerFault. If you know a better place for that task, please point me there. – cat pants Apr 26 '12 at 19:23
That, my friend, is part of your job if you're a sysadmin. Find hardware yourself, or find a vendor who can perform that service for you. Or find a more-scalable technology that efficiently allows you to get your work done. – Magellan Apr 26 '12 at 19:45
@catpants no it's not. In 6 months that list would be outdated. That's why things like this are explicitly not allowed. Much of the knowledge about RAID is generic and useful. When you get into specific product models and such it gets dated and useless very quickly. If you need a list of possible solutions for your project, you should contact a reseller/vendor and have them recommend something that will suit your needs. – MDMarra Apr 26 '12 at 19:45
Well, it would pretty much be guaranteed to be a subset of all cards that support this feature but at least it would be a starting point. My goal is just the same as other sysadmins: don't reinvent the wheel. – cat pants Apr 26 '12 at 22:40

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