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Is RAID still needed? (programming.dev)

submitted 7 months ago by [email protected] to c/[email protected]

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Me and my friend were discussing this the other day about how he said RAID is no longer needed. He said it was due to how big SSDs have gotten and that apparently you can replace sectors within them if a problem occurs which is why having an array is not needed.

I replied with the fact that arrays allow for redundancy that create a faster uptime if there are issues and drive needs to be replaced. And depending on what you are doing, that is more valuable than just doing the new thing. Especially because RAID allows redundancy that can replicate lost data if needed depending on the configuration.

What do you all think?

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[–] [email protected] 11 points 7 months ago (1 children)

Its very much still needed and heavily utilised in the enterprise world. Volume size is usually the lowest priority when it comes to arrays, redundancy and IOPS (the amount of concurrent transactions to the storage) is typically the priority. The exception here would be backup and archive storage, where IOPS is less important and volume size is more important.

As far as replacing sectors goes, I've never heard of this and I might just be ignorant on the subject but as far as I know you can't "replace" a bad sector. Only mark it as bad and not use it, and whatever was there before is gone. This has existed since HDD days. This is also why we use RAID - parity across disks to protect data.

Generally production storage will be in RAID-10, and backup/archive storage in RAID-6 or in some cases RAID-60 but I'm personally not a fan.

You also would consider how many disks are in the volume because there is a sweet spot. Too many disks = higher likelihood of total array failure due to simultaneous disk failures and more data loss in the event it does, but too few disks and you won't have good redundancy, capacity or performance either (depending on RAID level).

The biggest change I see in RAID these days is moving away from hardware RAID cards and into software-based solutions like Microsoft Storage Spaces, md, ZFS and similar. These all have their own way of doing things and some can even synchronise the data with other hosts.

Hope this helps!

[–] Blue_Morpho 4 points 7 months ago

As far as replacing sectors goes, I've never heard of this and I might just be ignorant on the subject but as far as I know you can't "replace" a bad sector.

Ssds maintain stats on cell writes and move data when a cell nears it end. They keep spare capacity hidden from end users for this. Not using part of the drive increases also this spare capacity.

However ssds do fail and moving data to spare cells doesn't change that.