iMac Pro iMac Pro SSD config

[zarf2007]

Hi,

got the base model iMac Pro and looking at other posts was led to believe that the 1TB storage would consist of 2 x 500GB SSD blades in a RAID 0 config. When I check under system information however it appears to be a single 1TB SSD blade.

Just checking if any other base model owners have the same? doesn't really bother me and tbh would prefer a single blade.

From system info:

APPLE SSD AP1024M:



Capacity: 1 TB (1,000,555,581,440 bytes)

TRIM Support: Yes

Model: APPLE SSD AP1024M

Revision: 114.37.2

Serial Number: C02747600JKJ803A4

Link Width: x4

Link Speed: 8.0 GT/s

Detachable Drive: No

BSD Name: disk0

Partition Map Type: GPT (GUID Partition Table)

Removable Media: No

Volumes:

EFI:

Capacity: 314.6 MB (314,572,800 bytes)

Available: 298 MB (298,033,152 bytes)

Writable: Yes

File System: MS-DOS FAT32

BSD Name: disk0s1

Mount Point: /Volumes/firmwaresyncd.p81CkC

Content: EFI

Volume UUID: E783267B-A4C3-3556-B751-DBED770EB996

disk0s2:

Capacity: 1 TB (1,000,240,963,584 bytes)

BSD Name: disk0s2

Content: Apple_APFS



thanks

Zarf

 

[FredT2]

Hi,

got the base model iMac Pro and looking at other posts was led to believe that the 1TB storage would consist of 2 x 500GB SSD blades in a RAID 0 config. When I check under system information however it appears to be a single 1TB SSD blade.

It is physically two separate sticks controlled by T2 chip, no RAID.

 

[zarf2007]

It is physically two separate sticks controlled by T2 chip, no RAID.

ah ok thanks

 

[RyanXM]

I would imagine the T2 Chip is making the separate physical drives into a LVG (Logical Volume Group). I haven't seen any evidence of it RAIDing them.

 

[wardie]

Does an LVG give you striping even if it’s not RAID0? I’m sure I saw some performance figures which indicated high speeds that you thought would only come from that type of config >2GB/s.

 

[RyanXM]

Does an LVG give you striping even if it’s not RAID0? I’m sure I saw some performance figures which indicated high speeds that you thought would only come from that type of config >2GB/s.

I'd have to dig into how the LVG handles the data transfers, but given that a "Fusion HD" is just an LVG group, software knows which volume is "faster", so I'd imagine you would see some benefits. Aren't write speeds higher than reads on the iMac Pro?

 

[curmudgeonette]

I would imagine the T2 Chip is making the separate physical drives into a LVG (Logical Volume Group). I haven't seen any evidence of it RAIDing them.

There's no significant controller on the individual SSD halves. Therefore, I suspect they are simply two banks of SSD chips. Just like two RAM DIMMs forming a 128 bit wide memory system.

 

[bplein]

So, if I told you it was one stick, or two, or 4... other than curiosity, what does it matter?

My solid bet is that the T2 is striping across 2 sticks. This gives better performance and write leveling BUT higher risk of failure. But you should be backing up regularly and even doubling the failure rate by striping across 2 devices is probably more reliable (lower failure rate) than a single HDD of old...

---- added later ----

By the way, a single SSD will stripe across many chips internally. More chips means more chances of failure, but higher performance. But you don't hear people complaining that several chips are used inside an SSD.