External SSD boot disc help

[Wrighty67]

Hi all

I have recently purchased an external 256gb ssd drive to use as a boot disc on my late 2013 iMac.

It is capable of speeds of up to 6gb/s in the specs.

I got it set up fine and cloned across with carbon copy cloner - all working fine.

Speed however is not what I expected - it appears faster than the internal, but on checking read/write speeds I am getting around 103 mb/s read and 95 write, which appears a long way short of what I expected.

USB 3 is working fine and system report showing speeds of up to 5gb/s.

I have reset SMC but no change.

Is there anything I may be missing in terms of settings that might be impacting speed?

Thanks in advance for any help.

Peter.

 

[Fishrrman]

It would help if you told us WHICH drive you bought.

Is this a "ready-to-use" drive, or was it a "bare" drive that you put into an enclosure?

Are you using it with a hub, or plugging it directly into the Mac?

An external USB3 SSD in an enclosure that supports UASP (USB attached SCSI protocol) should give read speeds around 430MBps and writes of 340MBps (or higher). The write speeds will vary with the drive's manufacturer, model, size, etc.

 

[tyc0746]

What SSD have you bought, is it a SATA SSD or a NVMe SSD in a USB enclosure?

What format have you set it up as - APFS, HFS+, ExFAT, NTFS, FAT32 - or have you just left it in the format it arrived?

I've got a Samsung Extreme USB3.1 one here, connected to a late 2014 iMac and it's giving about 420MB/s for both read & write (using a 5GB test file in Blackmagic Disk Speed Test) - and that's on an almost full, NTFS-formatted drive (using Paragon NTFS driver). Internal Apple SSD is giving about 620MB/s in the same test.

 

[Wrighty67]

It would help if you told us WHICH drive you bought.

Is this a "ready-to-use" drive, or was it a "bare" drive that you put into an enclosure?

Are you using it with a hub, or plugging it directly into the Mac?

An external USB3 SSD in an enclosure that supports UASP (USB attached SCSI protocol) should give read speeds around 430MBps and writes of 340MBps (or higher). The write speeds will vary with the drive's manufacturer, model, size, etc.

Thanks for the reply.

It's a generic (see link if that helps) that comes in an enclosure (ex of a laptop I believe)

External 256GB SSD 2.5" 6Gb/s - Fast Portable SSD Storage for PC, Laptop or Mac | eBay

Made with a lightweight and compact design, the case and the NEW 6Gb/s 7mm 256GB SSD will be unboxed and the unit assembled ready for you to just plug and play (As it runs from a USB 3.0 port, no external power source is needed).

www.ebay.co.uk

Plugged directly into iMac

 

[Wrighty67]

What SSD have you bought, is it a SATA SSD or a NVMe SSD in a USB enclosure?

What format have you set it up as - APFS, HFS+, ExFAT, NTFS, FAT32 - or have you just left it in the format it arrived

The product is in the link I posted above - hope that helps.

Its formatted to APFS as I was advised.

 

[tyc0746]

The product is in the link I posted above - hope that helps.

Its formatted to APFS as I was advised.

Strange, but your 3rd post appeared before the one with the link in!

It doesn't say what SSD is inside (only that it's from a laptop, and is refurbished), and as it is completely unbranded you may never know what you've bought...but I'd assume it's a simple SATA2/3 one from a scrapped laptop.

The fact that the seller is stating SATA speeds as the SSD speed, and listing multiple device brands in the description tells me the seller knows exactly what they're selling and are hoping less tech savvy buyers will snap it up just because it's cheap.

In fact, in some of his other listings the SSD read/write speed is listed...but in this it isn't...wonder why not?

I suppose you could return it as 'not as described' as your own speed tests have shown it's not the 6Gb/s SSD (which would be over 700MBps) as stated in the advert.

BTW, you've not turned encryption on have you, as I'm not sure what the overhead is on older, non-T2 iMacs....actually there was another post on here a couple of weeks ago where the initial speeds were slow...but I can't remember what the resolution was (I'll see if I can find it, it may help you after all).

ETA - the other post was simply due to a dodgy USB port, you could try another port just in case, as I think they're all 3.0 ports on that machine!

 

[Wrighty67]

Just out of interest - I have left the Blackmagic speed test running for the last 60 mins and the speed has increased to 220 read and 116 write for some reason
[automerge]1592060411[/automerge]

Strange, but your 3rd post appeared before the one with the link in!

I think that maybe they get moderated if there is a link..
[automerge]1592060853[/automerge]

Strange, but your 3rd post appeared before the one with the link in!

It doesn't say what SSD is inside (only that it's from a laptop, and is refurbished), and as it is completely unbranded you may never know what you've bought...but I'd assume it's a simple SATA2/3 one from a scrapped laptop.

The fact that the seller is stating SATA speeds as the SSD speed, and listing multiple device brands in the description tells me the seller knows exactly what they're selling and are hoping less tech savvy buyers will snap it up just because it's cheap.

In fact, in some of his other listings the SSD read/write speed is listed...but in this it isn't...wonder why not?

I suppose you could return it as 'not as described' as your own speed tests have shown it's not the 6Gb/s SSD (which would be over 700MBps) as stated in the advert.

I didn't have huge expectations for that price - I just wanted to make sure there was nothing obvious I was missing that would unlock its potential.

It's a fair bit faster than the original internal HD at least.

Thanks.

 

[Wrighty67]

BTW, you've not turned encryption on have you, as I'm not sure what the overhead is on older, non-T2 iMacs....actually there was another post on here a couple of weeks ago where the initial speeds were slow...but I can't remember what the resolution was (I'll see if I can find it, it may help you after all).

ETA - the other post was simply due to a dodgy USB port, you could try another port just in case, as I think they're all 3.0 ports on that machine!

No - just checked and it's off, as is Firewall.

 

[tyc0746]

I didn't have huge expectations for that price - I just wanted to make sure there was nothing obvious I was missing that would unlock its potential.

It's a fair bit faster than the original internal HD at least.

Thanks.

It's a bit of a gamble on ebay at that price, but it's half the cost of the cheapest branded one on Amazon (about £60 for the cheapest 256GB and £85 for the cheapest 500GB).

 

[Fishrrman]

Another suggestion:

ERASE it, this time as "Mac OS extended with journaling enabled", GUID partition format.

Connect and measure speed again.

Any difference?