Primary Storage

Hi guys,

I have a scenario where I can't afford to buy many FCM drives from the beginning. I could start to 3 FCM drives with D-RAID 1 (one rebuild area) and slowly growing to 8 drives in the future. I understand the D-RAID 1 efficiency with 2 or 3 drives but it's not very clear for me what happens for 8 drives. Is the same efficiency as using D-RAID 5 but using a smaller strip size ?

Thanks.

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Adrian Nicolae
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Hi,

This is what I found in documents: https://www.ibm.com/docs/en/flashsystem-7x00/8.4.x?topic=ac-distributed-array-properties-1

The effective capacity of a distributed RAID 1 array made from the same number of underlying drives as a RAID 5 or RAID 6 array is in general less than the effective capacity of the latter. However, while capacity-wise, distributed RAID 5 and 6 are generally better, performance-wise, RAID 1 may be better for certain workloads.

Best Regards, Denis.

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Denis Olshanskiy
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Original Message:
Sent: Tue May 31, 2022 01:13 PM
From: Adrian Nicolae
Subject: D-RAID 1 with multiple drives

Hi guys,

I have a scenario where I can't afford to buy many FCM drives from the beginning. I could start to 3 FCM drives with D-RAID 1 (one rebuild area) and slowly growing to 8 drives in the future. I understand the D-RAID 1 efficiency with 2 or 3 drives but it's not very clear for me what happens for 8 drives. Is the same efficiency as using D-RAID 5 but using a smaller strip size ?

Thanks.

------------------------------
Adrian Nicolae
------------------------------

Hi Adrian,
DRAID-1 with one rebuild area generally has capacity of number of drives (n-1)/2,
whereas DRAID-5 with one rebuild area would be like n-2 and n-3 for DRAID-6.
NB: For FS5200 respectively from a certain software version on, configuring any RAID-5 is not supported any longer

------------------------------
Christian Schroeder
IBM SpecV Storage Support with Passion
------------------------------

Original Message:
Sent: Tue May 31, 2022 01:13 PM
From: Adrian Nicolae
Subject: D-RAID 1 with multiple drives

Hi guys,

I have a scenario where I can't afford to buy many FCM drives from the beginning. I could start to 3 FCM drives with D-RAID 1 (one rebuild area) and slowly growing to 8 drives in the future. I understand the D-RAID 1 efficiency with 2 or 3 drives but it's not very clear for me what happens for 8 drives. Is the same efficiency as using D-RAID 5 but using a smaller strip size ?

Thanks.

------------------------------
Adrian Nicolae
------------------------------

Thanks. All clear now.

------------------------------
Adrian Nicolae
------------------------------

Original Message:
Sent: Wed June 01, 2022 05:02 AM
From: Christian Schroeder
Subject: D-RAID 1 with multiple drives

Hi Adrian,
DRAID-1 with one rebuild area generally has capacity of number of drives (n-1)/2,
whereas DRAID-5 with one rebuild area would be like n-2 and n-3 for DRAID-6.
NB: For FS5200 respectively from a certain software version on, configuring any RAID-5 is not supported any longer

------------------------------
Christian Schroeder
IBM SpecV Storage Support with Passion

Original Message:
Sent: Tue May 31, 2022 01:13 PM
From: Adrian Nicolae
Subject: D-RAID 1 with multiple drives

Hi guys,

I have a scenario where I can't afford to buy many FCM drives from the beginning. I could start to 3 FCM drives with D-RAID 1 (one rebuild area) and slowly growing to 8 drives in the future. I understand the D-RAID 1 efficiency with 2 or 3 drives but it's not very clear for me what happens for 8 drives. Is the same efficiency as using D-RAID 5 but using a smaller strip size ?

Thanks.

------------------------------
Adrian Nicolae
------------------------------