The rule is that you can have data disks in the RAID group
smaller that the largest data disk, and not cause the larger data disks to be down-sized, as-long-as the parity disks are the size of the
largest data disk. The smaller disk just get truncated.
Here are a few tests/examples:
TEST 1: Create an aggregate with 5 * 113.4MB SSD and
usable size = 233.8MB
TEST 2: Add a 527.6MB SSD to the aggregate created in
TEST 1, and - as expected - the disk would be downsized
TEST 3: Create an aggregate with 6 * 527.6MB SSD + 1 * 113.4MB
SSD and usable size = 1.83GB (not 389.5MB as might have been expected)
TEST 4: Create an aggregate with 7 * 527.6MB SSD and add
1 * 113.4MB SSD
TEST 5: What happens when we try to replace the 113.4MB
SSD with a 527.6MB SSD?
Test Results
TEST 1: Create an aggregate with 5 * 86.56MB SSD and
usable size = 233.8MB
CLU01::> aggr create -aggregate
TEST_SSD2 -disklist NET-1.37,NET-1.38,NET-1.39,NET-1.40,NET-1.41
Info: The layout for aggregate
"TEST_SSD2" on node "CLU01-01" would be:
First Plex
RAID Group rg0, 5 disks (block checksum, raid_dp)
Usable Physical
Position Disk Type Size Size
---------- ------------------------- ---------- -------- --------
dparity NET-1.37 SSD - -
parity NET-1.38 SSD - -
data NET-1.39 SSD 86.56MB 113.4MB
data NET-1.40 SSD 86.56MB 113.4MB
data NET-1.41 SSD 86.56MB 113.4MB
Aggregate capacity available for volume use would be 233.8MB.
TEST 2: Add a 500MB SSD to the aggregate created in TEST
1, and - as expected - the disk would be downsized
CLU01::> aggr add-disk -aggregate
TEST_SSD2 -disklist NET-1.8 -raidgroup rg0
Info: Disks would be added to aggregate
"TEST_SSD2" on node "CLU01-01" in the following manner:
First Plex
RAID Group rg0, 6 disks (block checksum, raid_dp)
Usable Physical
Position Disk Type Size Size
---------- ------------------------- ---------- -------- --------
data NET-1.8 SSD 86.56MB 527.6MB
Aggregate capacity available for volume use would be increased by 77.93MB.
WARNING: One or more disks to be added will be downsized.
TEST 3: Create an aggregate with 6 * 527.6MB SSD + 1 * 113.4MB
SSD and usable size = 1.83GB (not 389.5MB as might have been expected)
CLU01::> aggr create -aggregate
TEST_SSD -disklist
NET-1.1,NET-1.46,NET-1.47,NET-1.48,NET-1.49,NET-1.50,NET-1.51
Info: The layout for aggregate
"TEST_SSD" on node "CLU01-01" would be:
First Plex
RAID Group rg0, 7 disks (block checksum, raid_dp)
Usable Physical
Position Disk Type Size Size
---------- ------------------------- ---------- -------- --------
dparity NET-1.46 SSD - -
parity NET-1.47 SSD - -
data NET-1.1 SSD 86.56MB 113.4MB
data NET-1.48 SSD 500MB 527.6MB
data NET-1.49 SSD 500MB 527.6MB
data NET-1.50 SSD 500MB 527.6MB
data NET-1.51 SSD 500MB 527.6MB
Aggregate capacity available for volume use would be 1.83GB.
CLU01::> aggr show
Aggregate Size Available Used% State RAID Status
--------- -------- --------- -----
------- ------------
TEST_SSD 1.83GB
1.83GB 0% online raid_dp,normal
Image: The smaller data disk doesn’t affect the usable
size of the larger data disks, it just truncates!
TEST 4: Create an aggregate with 7 * 527.6MB SSD and add
1 * 113.4MB SSD
CLU01::> aggr create -aggregate
TESTSSD3 -disklist NET-1.6,NET-1.7,NET-1.52,NET-1.53,NET-1.54,NET-1.55,NET-1.56
Info: The layout for aggregate
"TESTSSD3" on node "CLU01-01" would be:
First Plex
RAID Group rg0, 7 disks (block checksum, raid_dp)
Usable Physical
Position Disk Type Size Size
---------- ------------------------- ---------- -------- --------
dparity NET-1.6 SSD - -
parity NET-1.7 SSD - -
data NET-1.52 SSD 500MB 527.6MB
data NET-1.53 SSD 500MB 527.6MB
data NET-1.54 SSD 500MB 527.6MB
data NET-1.55 SSD 500MB 527.6MB
data NET-1.56 SSD 500MB 527.6MB
Aggregate capacity available for volume use would be 2.20GB.
CLU01::> aggr add-disk -aggr
"TESTSSD3" -disklist NET-1.4 -raidgroup rg0
Info: Disks would be added to aggregate
"TESTSSD3" on node "CLU01-01" in the following manner:
First Plex
RAID Group rg0, 8 disks (block checksum, raid_dp)
Usable Physical
Position Disk Type Size Size
---------- ------------------------- ---------- -------- --------
data NET-1.4 SSD 86.56MB 113.4MB
Aggregate capacity available for volume use would be increased by 77.93MB.
CLU01::> aggr show
Aggregate Size Available Used% State RAID Status
--------- -------- --------- -----
------- ------------
TESTSSD3 2.27GB 2.27GB 0% online
raid_dp,normal
TEST 5: What happens when we try to replace the 113.4MB
SSD with a 527.6MB SSD?
CLU01::> disk replace -disk NET-1.4
-replacement NET-1.51 -action start
Warning: Replacement 520.5MB disk will be downsized
to 107.1MB. Continue? {y|n}: n
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