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Windows software RAID

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Before anybody says "software RAID sucks, go hardware", let me start by saying that you need expensive 3ware or adaptec adapters with on-board battery-backed RAM in order to have any big advantage over software raid (and most "hardware" RAID solutions are partially software anyway, usually just with an XOR accelerator engine).

So, the question is: does anybody here have experience with Windows' built-in software RAID? AFAIK it requires that you do 'dynamic' disk partitioning, has support for 0,1,5 levels, and is only supported on the pro/business versions... but that's as far as my knowledge of it goes.

So I'm wondering... can windows boot from a mirror RAID partition? And what is performance like? (I have a quadcore CPU, I don't suppose there's going to be much CPU strain unless you go RAID-5 which I'm not interested in). Does it offer the "striped read" optimization for mirrors (like intel raid matrix), or does it read from both disks and do compare?

I have a software raid....but on linux.  Because of power failures here that the UPS is unable to catch, that system crashes. Sometimes it crashes so badly that it has to 'rebuild' the data. The problem is that it can easily take two/three days (as in 48/72 hours!) to rebuild 1 TByte. The machine is in all this time inaccessible.

The setup is 4 250GB SATA2 harddisks (maxtor), 2GB RAM, OpenSuse 10.1 server, Athlon64 3400+, Asus K8N-E Deluxe motherboard. In it 4 years of service it has crashed like this more times than there are fingers on both of my hands.

Given the same choice today, I would go for hardware raid solution. In the end it is cheaper and a whole lot less hassle. Likely you will not encounter as much power failures as I do. Even if the rebuilding takes half the time under windows, I still would advise against going for a software raid. They sound nice in theory, but that is it.

I'm not laughing! I've had RAID hardware (Adaptec) malfunction and take out an entire array. The only way it could be 'fixed' was to do a recovery from external backups.

Windows mirroring provides acceptable performance on the server side.  I've got some departmental/small office installations (i.e. <= 25 users on WinServer2k3) that are performing quite nicely using software RAID-1. It does require you use 'dynamic' disk partitions. AFAIK, it does boot from the actual mirror partition.

Can't vouch for the desktop implementation since I'd rather just have a sane "recovery image & backup" procedure for those. I avoid RAID on desktops because it's expensive for what it gets you (unless you need striping for video or related media use) - and it tends to give you a false sense of security. Everybody I ever met who has RAID on their desktop box doesn't do backups because they think they're already protected.

Shades: is it the RAID rebuild or the filesystem fsck that takes the time, though? And what RAID level are you running? (RAID-5 would take a long time to rebuild, but I'm only considering a mirror and a stripe). I run a mirror on my linux fileserver, btw.

40hz: server and desktop windows versions should have the same RAID implementation, really - there's a lot of code shared between the two, so really the difference mostly comes down to different registry defaults and some add-on stuff for the server editions. I'm not seeing mirror as alternative to backups, but as a supplement. I was thinking of mirror for OS install + documents/source partition, and a stripe for messing with ISOs, game installs, etc - ie, the data that I wouldn't weep if I lost.

I don't want to lose data to anything but a disk crash, though.

So, how does the windows raid work? Does it create a "virtual disk" that you can then partition, or do you set up "per-partition" kind of raid?

No it is definitely the rebuilding of the RAID (10) that requires that time. That system boots from a separate harddisk, the set of RAID disks even has its own power supply and is always started before the computer itself starts.


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