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More LVM love - Journal of Omnifarious

Sep. 19th, 2008

10:19 am - More LVM love

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I must say again that I love LVM. I attached my new hard-drives to my fileserver while it was running, then I had to reboot it because the 3ware 9650SE-4LPML card seems to require that I use the 3ware BIOS setup utility to configure my RAID and doesn't seem to have a Linux utility to do it. But, being able to add the drives while the server was on still saved me about 45 minutes of downtime.

After the reboot, I started using LVM in earnest. I added the new array to the volume group, used pvmove to move all the filesystems to the new volume group (while they were in active use mind you) and then removed the old RAID array from the volume group. Standard LVM stuff. But I was able to do it all while the system was up and running.

Also, I had been using 64MiB allocation chunks, but with 3.18TiB of storage, that gets to be an unwieldy number of chunks. But LVM now has a feature that allows you to change the size of the allocation chunks. In my case, all of my physical volumes had an even number of chunks, and all the filesystems also consisted of a contiguous region with an even number of chunks (at least after I moved them they did) and so I was able to move to a more manageable 128MiB chunk size.

All this change only required about 15 minutes of server downtime. I'll likely have another 45 minutes or so as I switch the old array to RAID 0 (to make sure the wipe works thoroughly) wipe it and then remove all the disks and the card. Most of that will likely be taken up by getting the new disks into cages. That makes a total of about 50-60 minutes of downtime.

If 3ware had a RAID management utility that worked in Linux I could've done all this with 0 downtime so far, and likely only about 30 minutes of downtime in the future for physically moving the drives into cages.

If I had 8 hot-swap cages (4 for the old drives, 4 for the new), I could do it with no downtime.

Current Location: 2237 NW 62nd ST, 98107
Current Mood: [mood icon] accomplished

Comments:

From:(Anonymous)
Date:September 19th, 2008 06:40 pm (UTC)

3Ware has a Linux management tool.

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They call it 3dm2, and it is a daemon that is accessed via a web browser. I've been using it for what, seven years now?
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[User Picture]
From:omnifarious
Date:September 19th, 2008 06:51 pm (UTC)

Re: 3Ware has a Linux management tool.

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It's closed source, that hardly counts as software at all.

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From:(Anonymous)
Date:September 19th, 2008 10:50 pm (UTC)

Re: 3Ware has a Linux management tool.

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You stated, "If 3ware had a RAID management utility that worked in Linux I could've done all this with 0 downtime so far." That is demonstrably false.

There's a very big difference between "There was no Linux management app so my server suffered unavoidable downtime" and "There's a Linux management app (two, actually) supplied with the controller, but I refuse to that app for ideological reasons and as a result I *voluntarily* chose to suffer downtime"

Meanwhile, the 3Ware controller firmware is also closed source, as is the (rather limited in comparison) BIOS management app, yet apparently that doesn't stop you from using them.

It's not like you had to leave the app running once you were done doing your thing.

But hey, it's your time and downtime.
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[User Picture]
From:omnifarious
Date:September 20th, 2008 07:30 am (UTC)

Re: 3Ware has a Linux management tool.

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Oh, well, I didn't even realize that the management tool was there until you mentioned it. And then when I went to look at it, I was really disappointed to discover that it wasn't Open Source. They at least made their driver Open Source.

I tried running the stupid thing, and first it had some idiotic Java installer that probably scattered files all over creation without allowing them to be managed by the package management system. And after doing a few things it now won't talk to any of the controllers in my system causing all kinds of interesting errors to show up in my system log.

Typical of what I expect from proprietary software.

And your point about the BIOS and firmware is well taken. Though they don't have quite as perniciously obvious an effect on my system.

Anyway, after learning of the existence of their garbage software my opinion of them has dropped significantly. If their BIOS software and firmware are as badly written as the software installed on my system, it's a wonder the card even works at all. So, thank you for pointing it out.

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