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RAID 6 and Storage
We have a PE R820 with 16 900GB SAS drives and a H710P controller. Here's what i would like to do: use RAID 6 for the group of 16 disks then "in" the RAID 6 group, create separate disks (not partitions). We need some dedicated drives due to high I/O apps and i don't want those high I/O apps on the same disk as the VM's, backups and SQL DB's. If i config a VD for the OS and use 2 disks RAID 1, i lose a disk. IF i config another VD using the next 3 drives with a fault tolerant RAID, i lose a drive there and if i config another VD using the next 4 disks with a fault tolerant RAID, i lose another drive here too and so on. Is this possible?
theflash1932
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July 11th, 2018 12:00
I'll echo that ... if you are concerned with performance, then don't put them all in the same VD. Even if you put multiple VD's on the same disk group, you will be sharing IO's. You want to separate IO, separate the disks - two 8-disk RAID 10's, for example, would give you two IO pools to run apps in.
DELL-Daniel My
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July 11th, 2018 12:00
Hello
No, if all of the disks are in one large RAID 6 the controller will determine where to put the data.
If performance is a concern then I suggest you not use parity RAID levels like RAID 5 or 6. I think we have some information on the RAID levels in the controller manual.
http://www.dell.com/storagecontrollermanuals/
Thanks
Tek-Nerds
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July 11th, 2018 14:00
I'm not concerned about the performance of RAID 6 with the H710P. As i understand it, the h710P boosts the RAID 6 write times. Is this true?
If that is true, im not concerned about the performance of RAID 6 and want to use that RAID level; we can lose 2 drives and get the benefit of total capacity (which we desperately need). The point that i am concerned with if 1 big drive, i don't want to put the high IO apps to where they are accessing the 1 big drive. For example, SQL DB's backups and VM's, not a best practice to put those items on the same drive. I know, what we NEED is a powervault/SAN and i have proposed that but it is not in the budget.... So i am left trying to make this server fit these needs.
theflash1932
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July 11th, 2018 15:00
Fair enough, but you won't be able to truly separate the IO if they are all in the same disk group.
Tek-Nerds
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July 12th, 2018 19:00
OK, so i had to completely reconfigure the available 3 storage devices and the PEr820. I wanted to retire a legacy device but will instead use it for backup storage only and move the SQL DB's and logs from this legacy device to the r820 and here is what i am thinking about RAID configurations on the r820:
2 drives in RAID 1 for the OS
14 drives in RAID 10. Then create partitions for high IO apps. Since RAID 10 is highest read/write operations, will this fact nullify the high IO apps being on the same physical drive?
DELL-Daniel My
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July 13th, 2018 09:00
No, partitions in the operating system do not affect physical disk data placement. If you want to choose which physical disk(s) the data is placed on then you need to segregate the data using virtual disks on the controller.
That being said, one large RAID 10 is a good option for high I/O. RAID 10 does not use concatenation for data placement, so it does not fill up one drive and then move on to the next drive. When you write data to a RAID 10 it is striped across every disk. It does a stripe of data across all disks and then does another stripe across all of the disks. It writes data across all of the disks as if they were one large disk. The more disks there are in a RAID 10 then the more spread out the data and thus the I/O is. Large RAID 10s are a good option for spreading I/O across physical disks.