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RAID 1 and Dual Boot Partitioning Question

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May 26, 2009 4:31:27 AM

I have 2 questions.

Question 1: IF I purchased an ASUS M4A79T MB, and set up 2 SATA HD in RAID1, I should have the read performance of a RAID0, and just lack the write benefit. Right?

Question 2: If I used the ASUS M4A79T MB to RAID 1 on 2 HD, then installed Windows, would it be possible to resize that RAID array to partition off space for an Ubuntu install? If not, is it possible to partition off the Linux space initially? How is this best accomplished? Is this any different on RAID0?

Thanks in advance! Will check back in several hours.
May 26, 2009 7:40:11 AM

Answer 1: Take note that RAID1 is more for fault-tolerance than disk read speeds. But since your data is available from two disks, it's possible that you'll see a read speed increase. It all depends on what RAID controller you use.

Answer 2: Yes. So long as you computer activates RAID and starts reading your two hard disks as one drive during boot-up.

Hope this helps!
a c 127 G Storage
May 26, 2009 1:06:08 PM

There is no casual RAID1 implementation that reads from it like its a RAID0, those implementations i've seen only under Linux and BSD. Some hardware RAID might have them, but not even Areca (good hardware RAID controller) utilizes the full potential of RAID1.

So don't think it will make your system faster, you would have single-disk speeds and sometimes slightly below that. Also, not all linux can boot from onboard "Fake RAID" array, but a software RAID1 is bootable however. You can even mix RAID0 and RAID1 with the use of partitions, but that all doesn't work under Windows.

Another consideration is that a backup protects you against more dangers, so a RAID1 doesn't make that much sense for a home user IMO. Why not just use the second disk as backup and run without RAID?
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May 26, 2009 1:40:08 PM

Because HD space is so easy to come by, my goal was to RAID1 for 2 HD and hope to gain the usual performance boost of the RAID0 with the added benefit of fault tolerance. If I actually needed storage space, then of course I would use RAID0. As for backup, yes, I backup to an external HD. No sense in using an internal which is subject to anything that happens to the case itself.

Thanks for the replies.



**NEW QUESTION** - will a RAID0 array with two 7200RPM drives provide significant performance boosts over a single 7200 RPM drive. For example, I can buy a western digital caviar black 1TB drive for ~100, but I can buy a 500GB for about 60-70. At two, that is 20-40 to RAID0 the smaller drives into an equivalent space. Now, I know that the RAID array will transfer information at an absolutely faster rate, however I'm not running a server here, will I be able to sense the difference the RAID array makes for day to day use and for games, or would the difference not be that great?

thanks
a c 127 G Storage
May 26, 2009 2:18:58 PM

Yes and No.

With RAID0 you can increase both IOps and throughput (MB/s) of your drives, but it cannot make up for the high latency of mechanical disks. So things like booting, loading applications and other "random-like I/O" will be very slow on any mechanical disk whether in RAID0 or not. RAID0 increases performance only when there are 2 or more I/O requests waiting, the queue depth. Not all applications are written in a way that allows multiple disks to process different tasks. Many games are known to fall into this category.

Things like copy tasks, or simultaneously running I/O-heavy applications, will be quite a bit faster. But this performance increase is nothing when comparing the use of a modern SSD against a mechanical disk. The result is a much more fluent and responsive system. When comparing an SSD against a HDD, in the worst case the HDD is 100 times (10.000%) slower (30.000IOps against 300IOps). Also, the read latency is also many times smaller, like 0.01ms versus 9ms.

In the end it depends what you are going to do with your system and what you can afford, but SSDs will be commonplace pretty soon because besides being potentially extremely fast, it also provides for very reliable, vibration/shock resistant storage that uses very little power and because its so reliable because it has no moving parts, you can use it safely in conjunction with RAID0, which would amplify its effects even further.
May 26, 2009 3:08:36 PM

You have confirmed what I have suspected. Seek time and not throughput is what counts for every day usage and for gaming. Throughput is what matters for servers and heavy file R/W access.

For now, I'm going to simply add a single larger 7200RPM (not as expensive as 10k rpm, and larger capacity AND faster than 5400). I will forget about the RAID for now, and simply run normally. I will continue to watch SSD prices, and when I find a deal that is right, I'll buy, then convert over to that for my OS and keep my 7200RPM as a data drive. My backup will be to an external which I would use for backup even if I did RAID1, b/c I do not trust any drive which is inside the case and subject to catastrophic failure be it virus, fire, lightning etc...

Thanks for the help, I think I know the best way to go with this now.
!