SAS Harddrives

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Jörg Henninges posted this 21 January 2025

hello all...

as i own a pegasus1 r6 for almost a year now, i never run it in raid modes, just as a drive enclosure for some of my data disks. among them, a 14tb seagate exos x16 SATA spinner, which served me always fine.

i came across an offer of 10x 14tb wd ultrastar hc530 SAS drives for a really recent price and got 3 of them to have a testrun. 

to test everything with an SAS drive before the order arrive, i asked a friend who have an old 600gb sas 12gbit drive which he never used anymore.

the test went successfully and the 600gb drive was just recognized and usable, so no problem with the larger drives?

as they arrived, the ultrastar SAS drives werent recognized at first, after a shutdown of the pegasus, the where listet but just on of the 1,75gb platter inside of the drive was found but not useable.

as it cannot rely on the drive size (the 14tb seagate exos SATA was always fully available), i thought its maybe the controller which can't handle SCSI-6 commands (but why the 600gb drive?).

i decide to get a pegasus2 r4 and test the drives in this enclosure, same result...

couraged with the known exos SATA drives, i got another pair, which i found also almost as cheap as the ultrastar SAS drives and they worked that perfect, that i ordered another two for a total of 5 drives.

they are happily sync now for almost 30h at 35% with a total capacity of 42tb in a raid5 with one spare drive.

but the reason for my post is: does anybody have a clue, why the known good ultrastar SAS drives are not fully compatible with the pegasus1/2 ?

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R P posted this 5 weeks ago

Hi,

Be advised that while SAS drives may work on a Pegasus, they are not supported.

Also, I'm not sure if you can mix SATA and SAS drives in a Pegasus. This is not a design consideration for a SATA device.

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Jörg Henninges posted this 5 weeks ago

thanks for your reply.
i knew that it was a 50:50 chance to get a SAS drive running and was encouraged when the 600gb drive was fine. 

on the other hand, the controller chip inside of the pegasus is supporting SAS a/o SATA drives. thats what i found in a documentation.

the mixing with the 600gb SAS and other SATA drives wasn't the problem, they could be used side by side in my experimental setup. 

i tried with just the WDs which doesnt change the strange behaivor.

R P posted this 5 weeks ago

Hi,

Regarding the ultrastar hc530 SAS drives, from the spec sheet...

Capacity1 14TB ←
Interface SATA 6Gb/s: Sector size (bytes) - 4Kn:4096 512e: 512
Interface SAS 12Gb/s: Sector size (bytes) - 4Kn:4096, 4112, 4160, 4224, 512e:512, 520, 528

----

The Pegasus will support 4Kn, 512e and 512 byte sectors. If your SAS drives have any other sector size, the Pegasus won't work with the drives. Note, 4Kn drives will require a configuration change or rebuilds won't be able to start. There may be other issues that I am unaware of.

Jörg Henninges posted this 5 weeks ago

i attached a picture of one ofmthe drives...does it mean, a configuration change means a hardware or a software change? the drives run formerly in a dell das hooked on a windows machine...

R P posted this 4 weeks ago

Hi,

Well...

This drive is 4Kn, but with variable sector size, after some research this seems to be part of the 4Kn standard.

There was one case which I thought involved 4Kn drives, but now I'm not so sure.

I know that SAS drives can be used, but about 4Kn I'm now not so sure.

Are these drives visible in the Promise Utility?

 

 

 

Jörg Henninges posted this 4 weeks ago

yes, they are visible but just one of the 8 platter is recognized which explain the disk capacity of just 1,75tb of each drive.

R P posted this 4 weeks ago

Hi,

Sometimes a disk is not seen properly because of data already written to the disk. I've fixed some of these with macOS's dd command when the disk did not show up in the utility.

It might help if you run a quick init on the drive and restart the Pegasus.

Jörg Henninges posted this 4 weeks ago

problem is, the pegasus does recognize it, while macOS is not. 

a pass trough doesnt seem to work because there is a communication error reported, configuring the drive with 1,75tb as well, which seems logical to me.

when i plug the drives inside of my macpro5,1 ( with apple raid card ), i have to hide pin3 because of the known power issue, but the disks are not seen.

 

edit: planning to buy a lsi controller with breakout cable to get the disks run in my dell t3500.

R P posted this 4 weeks ago

Hi,

A quick init is run from the Promise Utility, it will by default zero out the first 64MB of the disk removing things like the disk label, partition maps and directory structure.

Please try a quick init and restart the Pegasus. The quick init function is in the background tasks tab.

Jörg Henninges posted this 4 weeks ago

i try this tomorrow. 

Jörg Henninges posted this 4 weeks ago

well, looks like i got rid of the three drives...they was bought on a flea market place where i offered them two days ago.

anyway, thanks for your help @R P !

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