I just installed another DAE (our second one) on a Celerra NX4 system. It has 12 x 600GB 15k RPM SAS drives. For best practices I'm trying to figure out how to carve out the storage.
On the DAE below it, I have a 6 disk RAID-5 and a 5 disk RAID-5 along with a hot spare. I was told not too long ago that a 6 disk RAID-5 performs slower than a 5 disk RAID-5.
So if I put 2 x 5 disk RAID 5's, I'm left with 2 extra disks.
What about the performance of RAID-6? Would 2 x RAID-6's be ok, or maybe 1 RAID-6 and 1 RAID-5 and 1 hot spare?
if this was my NX4 , i would continue to use the same approach and build 4+1 and a 5+1 RGs. I don't know how you feel about RAID-6 but i would not want to use it for VM datastores ..too much write penalty. I am curious why somebody would say that 5+1 is slower than 4+1 ? You have an extra spindle in 5+1, yes you might not have a pretty 256k stripe size but for random workloads like VM datastores i hardly doubt you would notice it. That's my 2 cents
I also threw around the idea of more disks in a raid 5 group. The thought was more spindles the better. But then again its larger size so it would take longer to rebuild or replicate / backup / move / etc..
So the 2 ~ 2.5 TB filesystems are still manageable when presented to VMWARE. Though it would be neat to see one giant file system and not think about where certain machines are stored (just pile them on there), I was always told not to be lazy and do something like that :-)
See that's my original thought as well. I was second guessing it when I was told that a 6 disk (5+1) raid-5 has more write penalty because it takes longer to calculate parity due to the extra disk????
Maybe this guy who told me that was mistaken?
Anyway if I keep it consistant..
The first 6 disks are RAID5 (5+1), present 3 equally divided LUNs off that, create a vm4-sas filesystem.
The second 5 disks are RAID5 (4+1), ''''', create vm5-sas filesystem.
Didn't know what you meant, but a quick search of Isilon shows me some cool stuff from EMC.
If money only grew on trees...
Wait, but would I still be here asking questions if my money grew on trees, rather than came from working in IT? Eh, its still a fun hobby - just would be limited in hours.
Anyway the NX4 can't do RAID-10 can it? I see an option for RAID1/0 but that slash in the name leads me to believe its not real raid 10. More like striping / no mirror.
But when I pick RAID1/0 it says 8 disks are reccomended. (Options are 2,4,6,8,10,12).
Again its that slash in the name RAID1/0 that has me worried its not RAID10 (no slash between the 1 and 0).
I also threw around the idea of more disks in a raid 5 group. The thought was more spindles the better. But then again its larger size so it would take longer to rebuild or replicate / backup / move / etc..
So the 2 ~ 2.5 TB filesystems are still manageable when presented to VMWARE. Though it would be neat to see one giant file system and not think about where certain machines are stored (just pile them on there), I was always told not to be lazy and do something like that :-)
dynamox
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Posted January 17th, 2013 06:00
if this was my NX4
, i would continue to use the same approach and build 4+1 and a 5+1 RGs. I don't know how you feel about RAID-6 but i would not want to use it for VM datastores ..too much write penalty. I am curious why somebody would say that 5+1 is slower than 4+1 ? You have an extra spindle in 5+1, yes you might not have a pretty 256k stripe size but for random workloads like VM datastores i hardly doubt you would notice it. That's my 2 cents 