RAID 1+0 - SSDs for...
 
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RAID 1+0 - SSDs for the working discs, HDD for the mirror

(@mustgroove)
Eminent Member Customer

There's a page on the Softraid site ( https://srforums.wpengine.com/pages/features/raid_uses.html#raid1) which says:

One way to create a faster mirror volume is by using an SSD for your working disk, and a mechanical hard drive for your mirror volume. The SSD gives you incredibly fast read speeds and the hard drive gives you safer storage, protecting your mirrored files from disk failure. (SoftRAID has complete support for SSDs)

Does this also apply to RAID1+0? Could I set up a RAID 1+0 where the main/working pair are SSDs for maximum working speed, and the mirror pair are HDDs to save money?

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Topic starter Posted : 21/02/2018 6:25 pm
(@softraid-support)
Member Admin

Yes you can. In fact, I believe this is a configuration that OWC offers with the Thunderbay Mini. 2 SSD's and 2 HDD's. when you configure the RAID 1+0 volume, SoftRAID automatically selects the SSD's to be the primary disks and uses them for reads.

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Posted : 22/02/2018 4:29 am
(@mustgroove)
Eminent Member Customer

Yes you can. In fact, I believe this is a configuration that OWC offers with the Thunderbay Mini. 2 SSD's and 2 HDD's. when you configure the RAID 1+0 volume, SoftRAID automatically selects the SSD's to be the primary disks and uses them for reads.

Thanks! So in that case, my followup question is how to go from my existing RAID 5 to a RAID 1+0 without getting a whole new enclosure to migrate to. Would the best move be to:

- Clone my existing data to a new drive
- Remove 2 of my current discs and replace with SSDs
- Set up a new RAID 1+0 volume
- Clone the data back to the new volume

Or is there a simpler/better way?

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Topic starter Posted : 22/02/2018 8:32 am
(@softraid-support)
Member Admin

You cannot, so the best plan is cloning to a new drive, creating the RAID 0 with the SSD's, copying the data back, then putting in the new HDD's and converting to RAID 1+0.

Note: you need to create a stripe first, not a mirror, to convert to a RAID 1+0.

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Posted : 22/02/2018 12:48 pm
(@mustgroove)
Eminent Member Customer

You cannot, so the best plan is cloning to a new drive, creating the RAID 0 with the SSD's, copying the data back, then putting in the new HDD's and converting to RAID 1+0.

Note: you need to create a stripe first, not a mirror, to convert to a RAID 1+0.

Thanks - finally setting this up now and I've got a couple of questions:

1) I selected the stripe to be optimised for Digital Audio on the setup page, but then it asks for a specific stripe size. From the available options, the 128KB option is said to be recommended for working with audio, but in the help file "What is a volume optimization?" section, it says:

The default stripe unit size when creating a new stripe volume is set to the smallest size which SoftRAID supports. This ensures that disk i/o does not starve the buffers on some digital audio PCI cards.

So should I actually set it to 16KB rather than 128KB?

2) When setting it up as you've suggested (set up stripe first with the SSDs, then convert to RAID1+0 to mirror to the HDDs), it starts a rebuild as soon as I convert to RAID1+0, even though the volume is empty. Is this normal?

3) I started copying my data back to the new volume before the rebuild was complete, and then the rebuild basically stopped completely, and stayed stopped overnight. I manually cancelled and restarted the rebuild, but it didn't get far before it stopped again. Will this rebuild eventually start again? Or should I let the initial rebuild finish before putting any data back on the volume?

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Topic starter Posted : 11/03/2018 12:07 pm
(@softraid-support)
Member Admin

If you intend to later convert a RAID 0 volume to a RAID 4 volume, you must select 16k Stripe unit size. We cannot convert any other kind of RAID 0 to RAID 4.

RAID 1+0 is different, and RAID 0 volume can be converted to RAID 1+0.

2. Yes it is normal. If a volume is "empty", then don't use convert, just create a new volume that is RAID 1+0. But a rebuild will rebuild the entire volume, in the background, so not to worry.

3. Is your volume mounted? Or damaged in some way? it should be able to rebuid.

Another idea is if you set it for Digital Photography, then the rebuild will pause any time you use your computer, to prevent the background task from interfering with your work. You can change it to workstation to stop this behavior, this setting can be changed at any time.

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Posted : 11/03/2018 11:57 pm
(@mustgroove)
Eminent Member Customer

If you intend to later convert a RAID 0 volume to a RAID 4 volume, you must select 16k Stripe unit size. We cannot convert any other kind of RAID 0 to RAID 4.

That's cool, I didn't realise RAID 0 could be converted to RAID 4 in this way. If I set it up as RAID 1+0 with 16KB stripe size, is this also possible down the track by removing the mirror discs from the volume (and essentially turning it back into a RAID 0) before converting to RAID 4?

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Topic starter Posted : 12/03/2018 10:44 am
(@softraid-support)
Member Admin

Yes you could, into a 3 disk RAID 4.

SoftRAID has the ability to convert a 4 drive RAID 1+0 into a RAID 4 volume directly, if the stripe unit size is 16K. The result is a 3 drive RAID 4 volume.

SoftRAID can also convert a RAID 4 volume into a RAID 1+0 volume, by adding a disk.

What we cannot do is convert a RAID 1+0 volume into a RAID 0 volume.
(this is technically possible, just not a feature n the GUI.)

So the answer for you is yes. Use the "Convert" feature.

You will see the option for RAID 1+0 in the dialog box.

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Posted : 12/03/2018 12:23 pm
(@mustgroove)
Eminent Member Customer

Sorry I what I mean is, is this possible:

- set up a 4-disc RAID 1+0 with a 16kb stripe size
- remove the 2 mirror discs (essentially "converting" the volume to plain RAID 0)
- add new discs and convert to RAID 4

Or does the volume have to be "pure" RAID 0 (with 16kb stripe size) to ever be possible to convert to RAID 4?

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Topic starter Posted : 12/03/2018 12:44 pm
(@softraid-support)
Member Admin

I updated my post to make a clearer reply.

thanks!

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Posted : 13/03/2018 1:21 pm
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