There, I have a significant choice — to use the on-board RAID, or do it entirely in software (e.g. OpenMediaVault)?
If you use hardware RAID -- especially one built-in to a motherboard -- and the hardware dies, you're screwed. Using software RAID, like the LVM Raid Linux provides, makes your RAID configuration hardware independent allowing you to move your disks to another system as you want/need. If you decide to use HW RAID, get a well-known dedicated RAID card that you can replace more easily than the motherboard with built-in RAID.
Still, there is a lot to be said for some of the off-the-shelf home RAID boxes. I haven't researched them, but I know a friend like the Synology NAS boxes. Most of those types of solutions are really Linux systems, but whether it's really software or hardware, I don't know, so I don't know if you could pull the drives and use Linux to recover your data. That should be a standard question to ask vendors before purchasing, but I doubt many people consider it.
I have a couple of Dell systems at home that have HW RAID on the motherboard and wondered if I should use them and my research made me decide against it (for the reasons I mentioned earlier). The documentation seems to indicate that these on-board systems are kind of picky, requiring (or strongly recommending) you use the exact same disks, etc... and it's unclear if disks could be moved to different model system. Even for a Windows system, using the SW mirroring Windows provides seems like the better choi
I'm admin for some online servers running on older Dell server chassis, Dell "PERC" HW RAIDs. One MB fried (impressive smoke residue inside the lid) and I simply pulled the drives, popped them into an older chassis, and it booted up and ran (Windows). I forget if it was the same PERC version controller (PERC 3, 4, 5...) but it just plain worked.
I've mixed and matched drive brands, sizes, etc. When you create the array (RAID 5 (or 6)) your array will be limited to the size of the smallest drive (times the number of drives minus one), but the extra space on the larger drives will be available to make another smaller RAID, or just as drive partitions.
The Open Manage sw that Dell distributes works pretty well, but it's pretty specific in that you have to match the OM version to the Dell PERC controller you have.
HP are also generally good, the metadata is stored on the disks themselves so if you move them to another similar controller it will detect the array and boot it.
Some servers actually have proper raid controllers built in, what you want to avoid is "fakeraid" which is a proprietary version of software raid that just happens to be implemented in the bios and have its own drivers.
Back in the day, there was no metadata written to the disks. If we had to pull the disks, we had to keep track of where they went or the array controller would treat the array as failed.
I don't know what took so long to get metadata written to disks. In theory the entire array configuration could almost not exist in the controller's memory, and just be read from the disks part of the total array integrity check at startup.
Despite this, even the "high end" PERC-type controllers are still somewhat stupid an
The low end Dell PERC RAID cards perform really badly for RAID 5 (anything other than RAID 0 or 1 really). Unless you are splashing out for a fairly high end HW RAID controller, you are probably better off using software RAID.
Yeah, thanks. It's all older hardware, on a tight budget, but all works well. Yes, all RAID 5. RAID performance is pretty good, not the bottleneck. But I agree- they seem much slower than they should be. I have some Mylex RAID controllers I've wanted to try someday. I used them a lot in the 90s and they were lightning fast.
The CPUs are likewise older and slower and I'm not sure if sw RAID would do well, as the CPUs get saturated running php crap.
All that said, I have newer much faster machines sitting
"The pyramid is opening!"
"Which one?"
"The one with the ever-widening hole in it!"
-- The Firesign Theatre
Software RAID (Score:5, Informative)
There, I have a significant choice — to use the on-board RAID, or do it entirely in software (e.g. OpenMediaVault)?
If you use hardware RAID -- especially one built-in to a motherboard -- and the hardware dies, you're screwed. Using software RAID, like the LVM Raid Linux provides, makes your RAID configuration hardware independent allowing you to move your disks to another system as you want/need. If you decide to use HW RAID, get a well-known dedicated RAID card that you can replace more easily than the motherboard with built-in RAID.
Re: (Score:2)
THIS!
Still, there is a lot to be said for some of the off-the-shelf home RAID boxes. I haven't researched them, but I know a friend like the Synology NAS boxes. Most of those types of solutions are really Linux systems, but whether it's really software or hardware, I don't know, so I don't know if you could pull the drives and use Linux to recover your data. That should be a standard question to ask vendors before purchasing, but I doubt many people consider it.
Re: (Score:3)
I have a couple of Dell systems at home that have HW RAID on the motherboard and wondered if I should use them and my research made me decide against it (for the reasons I mentioned earlier). The documentation seems to indicate that these on-board systems are kind of picky, requiring (or strongly recommending) you use the exact same disks, etc... and it's unclear if disks could be moved to different model system. Even for a Windows system, using the SW mirroring Windows provides seems like the better choi
Re:Software RAID (Score:3)
I'm admin for some online servers running on older Dell server chassis, Dell "PERC" HW RAIDs. One MB fried (impressive smoke residue inside the lid) and I simply pulled the drives, popped them into an older chassis, and it booted up and ran (Windows). I forget if it was the same PERC version controller (PERC 3, 4, 5...) but it just plain worked.
I've mixed and matched drive brands, sizes, etc. When you create the array (RAID 5 (or 6)) your array will be limited to the size of the smallest drive (times the number of drives minus one), but the extra space on the larger drives will be available to make another smaller RAID, or just as drive partitions.
The Open Manage sw that Dell distributes works pretty well, but it's pretty specific in that you have to match the OM version to the Dell PERC controller you have.
Re: (Score:2)
HP are also generally good, the metadata is stored on the disks themselves so if you move them to another similar controller it will detect the array and boot it.
Some servers actually have proper raid controllers built in, what you want to avoid is "fakeraid" which is a proprietary version of software raid that just happens to be implemented in the bios and have its own drivers.
Re: (Score:2)
Back in the day, there was no metadata written to the disks. If we had to pull the disks, we had to keep track of where they went or the array controller would treat the array as failed.
I don't know what took so long to get metadata written to disks. In theory the entire array configuration could almost not exist in the controller's memory, and just be read from the disks part of the total array integrity check at startup.
Despite this, even the "high end" PERC-type controllers are still somewhat stupid an
Re: (Score:2)
The low end Dell PERC RAID cards perform really badly for RAID 5 (anything other than RAID 0 or 1 really). Unless you are splashing out for a fairly high end HW RAID controller, you are probably better off using software RAID.
Re: (Score:2)
Yeah, thanks. It's all older hardware, on a tight budget, but all works well. Yes, all RAID 5. RAID performance is pretty good, not the bottleneck. But I agree- they seem much slower than they should be. I have some Mylex RAID controllers I've wanted to try someday. I used them a lot in the 90s and they were lightning fast.
The CPUs are likewise older and slower and I'm not sure if sw RAID would do well, as the CPUs get saturated running php crap.
All that said, I have newer much faster machines sitting