RAID SETTINGS | dual enclosure*

Here’s a breakdown of the main differences between JBOD, RAID 0, RAID 1, and BIG (sometimes referred to as SPANNING):

1. JBOD (Just a Bunch of Disks)

• Function: Combines multiple physical disks into a single virtual disk, but they remain separate within the system. Data is stored sequentially across disks without redundancy.
• Performance: Similar to using individual drives; no speed improvements since disks are accessed one at a time.
• Fault Tolerance: None. If one disk fails, only the data on that disk is lost; other disks remain unaffected.
• Use Case: Good for storing different types of data on each disk independently, without any need for redundancy.

2. RAID 0 (Striping)

• Function: Splits (or "stripes") data across multiple disks, so parts of each file are written to each disk. This improves read and write speeds since data can be accessed in parallel.
• Performance: High; data is written and read across multiple disks simultaneously.
• Fault Tolerance: None. If one disk fails, all data is lost because each file is split across all disks.
• Use Case: Best for scenarios needing high performance, like video editing or temporary storage, where data loss is acceptable.

3. RAID 1 (Mirroring)

• Function: Creates an exact mirror of one disk on another, effectively creating a copy. Every write operation is duplicated across both disks.
• Performance: Moderate; read speeds may improve as data can be read from either disk, but write speeds can be slower since data is written twice.
• Fault Tolerance: High. If one disk fails, data remains safe on the other disk.
• Use Case: Ideal for critical data storage where redundancy is essential, such as small business servers or personal backups.

4. BIG (Spanning)

• Function: Combines multiple drives into a single large virtual drive, filling one disk entirely before moving on to the next. Data isn’t striped but rather stored sequentially across disks.
• Performance: Minimal performance gain since data is stored sequentially and doesn’t span multiple disks simultaneously.
• Fault Tolerance: None. Similar to JBOD, if one disk fails, only the data on that disk is lost, not the entire volume.
• Use Case: Useful when you need a single large volume for storage but don’t need performance improvements or redundancy.

Summary

• JBOD: Combines disks without redundancy, treating each as a separate storage area.
• RAID 0: Stripes data for performance, no redundancy.
• RAID 1: Mirrors data for redundancy, moderate performance.
• BIG/Spanning: Combines disks into one large volume without redundancy or performance boost.

 

 

 

You said:

so they all suck? I have to use this cofig for time machine backups – al lother disks are too small – so I;'m tihnkign Big/Spanning?

 

ChatGPT said:

ChatGPT

If you’re using these disks for Time Machine backups and are limited by disk size, BIG/Spanning can actually work well for this purpose, with a few considerations:

Why BIG/Spanning for Time Machine?

1. Larger Combined Storage: Spanning (BIG) allows you to combine multiple smaller disks into one large virtual volume, providing the capacity Time Machine needs without the strict requirements of redundancy or speed.
2. Simplicity: Unlike RAID configurations, which require all disks to be the same size and often more technical setup, BIG is straightforward. The disks fill up sequentially, so you can add as many as you need to meet your storage target.
3. Acceptable Risk for Backups: While BIG doesn’t provide redundancy, Time Machine is designed to keep historical versions of files. The risk of losing one disk only affects the backup set on that disk; it doesn’t harm the data on your primary machine. You can always add another drive in the future if needed.

Things to Consider

• Drive Failure: While BIG won’t offer protection against disk failure, Time Machine can be forgiving if you have other backups or don’t mind the loss of older versions stored only in Time Machine.
• Management: When a disk in a BIG setup fails, Time Machine will continue working with available disks, but you may need to swap the faulty disk to regain full capacity.

Alternative: JBOD with Independent Time Machine Disks

If you’re concerned about the risk of spanning, an alternative could be setting up individual disks as separate Time Machine destinations (essentially JBOD). Time Machine will alternate backups between each drive, reducing the load on any single disk and offering a bit of separation in case one drive fails.

Verdict

BIG/Spanning should work fine if you’re okay with the potential risk, especially since it sounds like maximizing storage is a top priority. It’s a pragmatic choice for your Time Machine setup given the disk size limitations, as long as you’re aware of the potential trade-offs.

 

 

In that case, BIG/Spanning is likely the best fit. Here’s why:

1. Creates a Single Large Volume: BIG combines your disks into a single large virtual drive, allowing Time Machine to see and use them as one continuous space. This setup maximizes storage from all disks, which sounds ideal since individual disks are too small on their own.
2. Efficient Use of Space: Spanning lets Time Machine fill each disk sequentially, effectively utilizing every bit of storage without complicated configurations. It’s simple to set up and doesn’t impose the strict size-matching requirements of other RAID setups.
3. Trade-offs: While BIG/Spanning doesn’t offer redundancy, Time Machine backs up historical versions on a best-effort basis, so losing one disk won’t impact the data on your main machine. If you’re comfortable with the possibility of potentially losing some older backup versions, BIG/Spanning should give you the space you need for comprehensive Time Machine backups.

This approach provides a straightforward solution to combine your disks for the most storage possible, without requiring extra equipment or a full reconfiguration.