Can you RAID with SSD and HDD in 1+0 or 10 configuration

[wimpyjoe]

I have, currently, a RAID 0 configuration with 2 7200 RPM drives in SATA 2.0. I am planning to either buy 2 SSD 64 GB and RAID 0 or 2 SSD 120 GB SATA II in RAID 0. If it is possible, can you configure thet RAID 0 on the HDD, RAID 0 on the SSD, and then place both in RAID 1? Or do you have to just leave both HDD and SSD in RAID 0? And if so, do i gain any performance in RAID 0 in SSD with SATA II or should i jump to SATA III?

 

[Rusting In Peace]

While possible that's a terrible idea as the raid array will perform as fast as the slowest drive.

Don't mix regular HDD and SSD in raid arrays.

And SATA 2 will be fine for your SSD.

 

[jitpublisher]

Yeah, it is possible, however its a terribly bad idea. Besides the performance thing, your total drive size would be limited to twice the size of the SSD. All the extra space on the HDD would not be used. There are also many secondary considerations like defrag and indexing which should not be used on SSD's as they can affect the life of the drive considerably and provide no real performance benefit, but yet these services should be used on standard drives to enhance performance. Do you fully understand exactly what RAID means and what it does? Your questions suggest that you lack a of basic understanding of how SSDs, HDD's, and RAID actually works.

To expand a little more, its not a good idea to put SSD's in RAID either. You cannot use TRIM if you RAID them, which will actually hinder performance and possibly decrease the usable lifespan of the drive. SSD's are so fast anyway, they are nearly "instant", you won't gain any noticeable performance by putting them in RAID.

 

[wimpyjoe]

I understand how RAID 0, 1, and 5 works with HDD. I heard about the TRIM issue with SSDs if they are set in RAID. So since my HDD are in RAID 0 at this moment, I might go with just 1 SSD 128 GB SATA II. Since they are in RAID 0, will I still be able to use caching with the SSD without having to eliminate RAID?

 

[cirdecus]

In order to take two physical raid groups (your SSD RAID and your 7200rpm RAID) and make a top level RAID with them, you need to do it on the software level.

So you would configure your raid for both disk groups through your on-board controller. Then you would need a third party program in windows to view both raid groups and make a third raid. The problems are many:

1) You can't boot from a software raid, because it requires being in a windows environment to work. So no nested RAID groups on boot drives.

2) Both VIRTUAL raid groups must be identical in size. You can't setup a RAID 1 between two disk groups that are different sizes. I imagine that your 7200rpm RAID0 is a different size that what your SSD RAID0 would be. Nested RAID follows the same rules of physical RAIDs.

Typically, in a high performance desktop, you want to design your storage like this:

Two disks or disk groups:

1st Disk group should be a fast, low capacity volatile group.
2nd Disk group should be a slow, high capacity, highly redundant group.

You would install windows, programs (like office, photoshop, etc) and games on the first group, then store your music, movies, pictures, game saves and other information on the second group.

For the first fast group, you would aim for a single SSD that maxes out your controller's speed (one 500MB/s or greater SSD or two SATAII SDD's in a RAID0 (Dont think that you can achieve theoretical SATAIII speeds in a RAID0. The speed is limited by the crappy on-board Marvell controller. You won't get >1GB/s speeds with an onboard controller by putting two vertex 3's in a RAID0, regardless of how many SATAIII ports and SSD's you have.

For the second disk group, aim for a couple of 2TB 7,200rpm drives in a RAID1. I know it's tempting to double your storage, but AVOID RAID0 on this disk group. Putting your second group in a RAID0 completely defeats the purpose of this design.

With this setup, you won't need to backup your primary group. All data on that group can be reinstalled if lost (and should be periodically for speed). Your second group can handle a hard drive failing, which should give you time to find a replacement and rebuild the raid before the other one fails.

Remember, if you buy two identical drives that are manufactured about the same time, expect them to fail about the same time as well. I manage a 64 disk SAN at work and I can say that once one fails, you should be expect the rest to fail shortly after.