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Using disk space outside of RAID 0

W

WangChung

Limp Gawd
Joined
Dec 19, 2013
Messages
181
Scenario:

My laptop (HP 15t-j000) has a Samsung 840 Pro 256GB SSD, and I just bought a Samsung 840 EVO mSATA 250GB SSD as an upgrade to the ADATA I currently have. Sadly, Samsung doesn't make a 256GB mSATA, but I got a great deal on it (~$100).

I plan on putting the drives in RAID 0 using the Intel RST but I'm wondering if it's possible to use the drive space outside of the RAID? Is there any performance hit for doing so? I figured I could use this space as swap space or something.

Thanks for the help!
 
No, I don't believe Intel RST (or most hardware RAID cards) is capable of this. You can do it with some software RAID.
 
WangChung said:
Scenario:

My laptop (HP 15t-j000) has a Samsung 840 Pro 256GB SSD, and I just bought a Samsung 840 EVO mSATA 250GB SSD as an upgrade to the ADATA I currently have. Sadly, Samsung doesn't make a 256GB mSATA, but I got a great deal on it (~$100).

I plan on putting the drives in RAID 0 using the Intel RST but I'm wondering if it's possible to use the drive space outside of the RAID? Is there any performance hit for doing so? I figured I could use this space as swap space or something.

Thanks for the help!
Click to expand...

Are you referring to the left over 6GB on the 256GB SSD? If so there is no way to use it afaik, I'd be shocked if it is even possible with software RAID
 
I'd be shocked if it is even possible with software RAID
Click to expand...

You can do this in linux since sometime in the 1990s. All you do is create the raid on partitions not the whole disk. Windows builtin raid should also support this.
 
MySongRanHills said:
Are you referring to the left over 6GB on the 256GB SSD? If so there is no way to use it afaik, I'd be shocked if it is even possible with software RAID
Click to expand...

It is possible with some software implementations. There are several software RAID implementations that do not (or do not have to) work on an entire volume. Heck, even ZFS doesn't need a whole volume. LVM can do it and it might be possible with DMRAID as well.

Likely not possible with Microsoft's.
 
dandragonrage said:
It is possible with some software implementations. There are several software RAID implementations that do not (or do not have to) work on an entire volume. Heck, even ZFS doesn't need a whole volume. LVM can do it and it might be possible with DMRAID as well.

Likely not possible with Microsoft's.
Click to expand...

Thats pretty interesting, learned something new today. Makes sense though when thinking in terms of partitions and not disks.
 
You could do this under the Intel "Matrix RAID" functionality, where you can setup (for example) RAID 0 & Raid 1 on the same disk pair. Unfortunately, this killed any performance benefit you would see in a native spinning-disk R0, so there is no real benefit to it. You could, in theory, setup a 250GB R0, then temporarily add a third drive. Add the 6GB left to a R1 with 6GB of the temporary third drive, pull the third drive and then you would have a 250GB R0 and a failed (though usable) 6GB R1. As I said, this is theoretically possible and you should never, ever do something like this. All of that being said, outside of synthetic benchmarks, you see almost no real world noticeable improvements with a two drive R0 Boot OS SSD array, especially on dissimilar hardware. Make the faster of the two drives your boot drive and use the other as a secondary volume.
 
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On my system I have 4x300gb raptors short-stroked RAID0 with the first 25GB for a 100GB temporary folder.

The rest of the space I have in a leftover RAID0 with my games installed. All windows software RAID Pic (http://i.imgur.com/LH9ybIJ.png)
 
MySongRanHills said:
Thats pretty interesting, learned something new today. Makes sense though when thinking in terms of partitions and not disks.
Click to expand...

The key is to stop thinking in terms of disks and partitions and instead reason about everything as a block device. Then your only limited by what you can represent as a block device.

Partitions, drives, and files (loop device) can all be represented as block devices, a RAID array simply takes many block devices and represents them as one block device. dm-crypt takes an ciphertext block device and represents it as an plaintext one. LVM takes block devices and represents them as PVs. An iSCSI target can be represented as a block device. Layer them, combine them, transform them, and so on.
 
RAID0 on SSD is almost always wasted effort, especially if two drives with such different performance characteristics are used.
Be sure TRIM works for your RAID0 setup, otherwise the EVO may slow down significantly over time.
I would keep the 6 GB unused, the 840 Pro actually does like a bit of overprovisioning, especially if TRIM does not work.
 
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