Striped RAID with 2 SSDs

[PliSsK]

Has anyone tried making a striped RAID with one SATA3 SSD and one M.2 NVMe SSD (rather than buy a larger SSD)? If so, what is the net result, does it default to SATA3 speeds or does the r/w speed depend on which drive is being written to at any given time? Thanks.

 

[jaymonkey]

Has anyone tried making a striped RAID with one SATA3 SSD and one M.2 NVMe SSD (rather than buy a larger SSD)? If so, what is the net result, does it default to SATA3 speeds or does the r/w speed depend on which drive is being written to at any given time? Thanks.

@PliSsK,

Why would even want to do that ?

Creating a RAID 0 using a fast interface (NVMe) and a slow interface (SATA-3) would completely negate the whole point of RAID 0 which is to increase read/write speeds as the whole process would be slowed down by the SATA-3 SSD.

Some background information ...

All data is split into blocks, be it system files, applications or user data, the block size is defined when creating a RAID, if it's going to be for lots of small files (like an OS) then the block size can be as small as 4K, if its going to be only used for say large video files then the block size can be set to something like 512K

RAID 0 alternates the writing of all data blocks between the two drives :-

1st block to drive 0
2nd block to drive 1
3rd block to drive 0
4the block to drive 1

.... and so on.

So with RAID 0 every file has blocks saved on both drives, this means when reading a file blocks can read from both drives at the same time resulting in a greater read speed than a single drive. However blocks must be read concurrently so in this instance the NVMe SSD would be constantly waiting for the SATA-3 SSD to catch up.

RAID 0 expects two drives of the same type and size ...

Whilst it may still work (assuming MacOS even lets you create such a RAID 0) there would be no benefit speed wise and due to the different interface technologies a RAID 0 made up of a NVMe and a SATA-3 SSD would be IMO quite fragile and highly NOT recommended.

Cheers
Jay

 

[PliSsK]

Thanks for the reply. Sorry I think I meant spanned volume not striped volume. I think you are correct in strongly stating the case against a mismatched striped volume. The reason for asking is that after an upgrade I will have a couple of SSDs spare, and for my purposes I would like to have one bigger combined volume rather than use them individually, so I can transfer 840GB of data from an HDD to this. The other option would be to sell them and buy a larger SSD, preferably at the cheaper end of NVMe if I can get a good deal on one.

 

[jaymonkey]

Thanks for the reply. Sorry I think I meant spanned volume not striped volume. I think you are correct in strongly stating the case for against a mismatched striped volume.

@PliSsK,

Ok that makes a big difference, yes you could use miss matched interfaces and drives for a spanned volume, although i haven't tried it personally it should work fine. Obviously read/write speeds will depend upon which drive a particular file is on.

How to Combine Multiple Hard Drives Into One Volume for Cheap, High-Capacity Storage

Once you've gone through a few computers, you probably have more than a few old hard drives lying around. You don't have to let them go to waste, thou

lifehacker.com

Cheers
Jay

 

[PliSsK]

Thanks for the input. Once I've transferred my files over and wiped them, I guess I have nothing to lose in trying it. I understand that with spanned volume it will write to and fill up the first drive before writing to the 2nd one.

Edit: It worked fine creating the spanned JBOD volume, data on the first drive, the NVMe, was reading at approx. NVMe speeds.

@PliSsK,

Ok that makes a big difference, yes you could use miss matched interfaces and drives for a spanned volume, although i haven't tried it personally it should work fine. Obviously read/write speeds will depend upon which drive a particular file is on.

How to Combine Multiple Hard Drives Into One Volume for Cheap, High-Capacity Storage

Once you've gone through a few computers, you probably have more than a few old hard drives lying around. You don't have to let them go to waste, thou

lifehacker.com

Cheers
Jay