SC4020: assign a LOT of hotspare drives

Hello polezhaevdmi,

What is your current SCOS version?  How many disks are you adding into the system?  if you are using SCOS 7.3 or above then you will be using Distributed Sparing.  Here is a link to a white paper which explains how it works.  https://dell.to/3faVUkV

Here is also a link to the administrator guide & it talks about drive sparing on page 39.  https://dell.to/3lIFR0c

I cant help with your questions but

• You are aware that with SCOS 7.3 they introduced the feature Distributed spare?
• Instead of using multible hot spares you can use Double Redundancy for that tier
• Place the disk under the desk and use it as a replacement and insert when needed

Regards,
Joerg

Hello, Joerg!

>You are aware that with SCOS 7.3 they introduced the feature Distributed spare?

Yes, I'm, but that solution is not implemented at SCOS 7.2, which is active in the system now.

>Instead of using multible hot spares you can use Double Redundancy for that tier

Seems, this is the best variant among all possible. Still, the question regarding force hotspare assignment remaining. Extra 6x HDDs in my case allow to migrate correctly from RAID5-9 over 36x HDDs to RAID6-10 over 40x HDDs. The 2x HDDs still be reasonable to be assigned as extra hotspares.

>Place the disk under the desk and use it as a replacement and insert when needed

Yes, but this solution is the worst, because the physical state of HDDs in storage remains unknown for long period. Thus, Customer may run into a trouble, when the 'fresh drive' from 'under-the-desk store' appears actually dead.

Greetings, Sam L!

>What is your current SCOS version?  

System runs SCOS 7.2, thus, the Distributed/embedded Spare option still not available for it. The SCOS upgrade to 7.3+ is not possible now, and, seems, forever.

>How many disks are you adding into the system?  

Six 900GB, 10KRpm drives were added.

>Here is also a link to the administrator guide & it talks about drive sparing on page 39.

Yes, I investigated the actual guide before, and compared it with older SCOS (5.xx) version. Looks like some fuctionality dropped on a way to implement new features (like ability to select hotspares at disk folder creation). As for Page39 (and 40) - it describes not too much regarding the hotspare logics. For example, it's still not clear whether the hotspares are "global" (may be automatically used across all disk folders) or not.

He would like to know how many disks your SC have in total.   IIRC in the past the rule was that with every 21th disk a drive was marked as a hotspare.

Regards,
Joerg

Hello, Sam L!

>Hotspare drives are global on a compellent system.

Sam L, great thanks! That is the solution.

>How many drives do you have in total between SC4020 & your expansion enclosure?

System has all 48 slots populated: 3 SSDs and 45 HDDs (900GB / 10K). 40 HDDs now are placed in R6-10 protected tier, 3 HDDs are the hot-spares, designated at deployment. And 2 HDDs I left as hot-spares in the separate disk folder "HotSpares Only". All resources are assigned.

>hotspares are normally auto reserved by SCOS based on the  total# of drives in the system

Yes, but Customer requested a little bit more. And, seems the task is done.

> every 21th disk a drive was marked as a hotspare.

Customer needs much 'self-healing abilities' from the system. The double redundancy plus extra spares (which are global) - is excelent variant, thanks You!