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How to use a SoftRAID startup volume with High Sierra

If you're using High Sierra, and booting up from a SoftRAID volume, you'll need to follow the steps given in this forum post, since the macOS High Sierra Installer does not recognize SoftRAID volumes as valid startup volumes.

1st validate on new volume - LOTS of updated blocks
#1
Just wanted double check this:

1) I set up a new RAID 1+0 volume with the SoftRaid Easy Setup app. It has 4 discs - the 2 primary discs are SSDs, the 2 secondary discs are HDDs. In the Easy Setup app I chose "Digital Audio" for the volume optimisation, and it set a stripe size of 128KB.

2) I coped my data back onto the new volume

3) I validated the new volume overnight. When it was done, it had updated 175,753,559 blocks.

This seems super high - is there anything to be concerned about here? Why would so many blocks need updating when all I've done is just copy my data back to the volume?

I've just started another validation (which should surely result in zero updated blocks) and it's already updated 766.

My previous experience with SoftRaid has been a RAID 5 volume I used for years and years, and the first time I verified it I think the number of blocks that were updated was in the single digits, and then every subsequent validation (every few months) would end up with 0 updated blocks, so this is unusual from my experience.
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#2
The first time you validate, expect lots of updated sectors - normal.

The next time, you will get zero. Unless you have SSD drives, with TRIM enabled, which I suspect you have.

This is normal for SSD's with TRIM enabled, TRIM is always changing blocks in the background to keep the SSD write performance up.
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#3
(03-12-2018, 10:22 AM)SoftRAID Support Wrote: The first time you validate, expect lots of updated sectors - normal.

The next time, you will get zero. Unless you have SSD drives, with TRIM enabled, which I suspect you have.

This is normal for SSD's with TRIM enabled, TRIM is always changing blocks in the background to keep the SSD write performance up.

Yep TRIM is enabled on the SSDs. Would this ever be a problem? If TRIM is always causing changes that the mirror discs might not have caught up to, is that a possible issue in the event that an SSD fails?
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#4
TRIM is always updating sectors when the disk is inactive. What it effectively does is relocate and "erase" sectors, so the drive is faster when it is time to write data. (An SSD is relatively slow to "re-write" a sector)

SoftRAID is comparing raw data in every sector, so of course when SSD's TRIM, that causes the validation to show differences.

Validate will always show differences with SSD's.

Note:SSD's with TRIM enabled are extremely difficult to perform low level data recovery on if they fail. So backups are critically important.
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#5
(03-13-2018, 11:24 AM)SoftRAID Support Wrote: TRIM is always updating sectors when the disk is inactive. What it effectively does is relocate and "erase" sectors, so the drive is faster when it is time to write data. (An SSD is relatively slow to "re-write" a sector)

SoftRAID is comparing raw data in every sector, so of course when SSD's TRIM, that causes the validation to show differences.

Validate will always show differences with SSD's.

Note:SSD's with TRIM enabled are extremely difficult to perform low level data recovery on if they fail. So backups are critically important.

Thanks for that - so does this potentially create problems when a disc fails? Is it better from a data safety point of view to have TRIM disabled?
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#6
TRIM is generally better enabled.

If you have a total disk failure, TRIM SSD's are very difficult to recover from. More than a normal SSD, which are more difficult than a HDD. Just stay backed up!
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#7
(03-13-2018, 03:09 PM)SoftRAID Support Wrote: TRIM is generally better enabled.

If you have a total disk failure, TRIM SSD's are very difficult to recover from. More than a normal SSD, which are more difficult than a HDD. Just stay backed up!

Even SSDs in a RAID? So in the event an SSD dies for whatever reason, the array wouldn't just rebuild like it would with HDDs?

Had no idea this was the case, I thought RAID arrays coped with the failure of HDDs and SSDs equally well.
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#8
No, sorry, you are over-thinking. This does not refer to RAID, just to low level data recovery services, such as what Drive Savers.

When a HDD fails, they can often mechanically recover the data in a clean room.

TRIM enabled SSD's make it extremely difficult to do such recovery.
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