RAID configuration

[unni]

Please find my Virtual drive information below. Can i proceed to installation with this setup?

Adapter 0 -- Virtual Drive Information:
Virtual Drive: 0 (Target Id: 0)
Name :
RAID Level : Primary-1, Secondary-0, RAID Level Qualifier-0
Size : 557.861 GB
Sector Size : 512
Mirror Data : 557.861 GB
State : Optimal
Strip Size : 64 KB
Number Of Drives : 2
Span Depth : 1
Default Cache Policy: WriteBack, ReadAhead, Cached, Write Cache OK if Bad BBU
Current Cache Policy: WriteBack, ReadAhead, Cached, Write Cache OK if Bad BBU
Default Access Policy: Read/Write
Current Access Policy: Read/Write
Disk Cache Policy : Disabled
Encryption Type : None
Bad Blocks Exist: No
Is VD Cached: Yes
Cache Cade Type : Read Only




Virtual Drive: 1 (Target Id: 1)
Name :
RAID Level : Primary-1, Secondary-0, RAID Level Qualifier-0
Size : 1.088 TB
Sector Size : 512
Mirror Data : 1.088 TB
State : Optimal
Strip Size : 64 KB
Number Of Drives per span:2
Span Depth : 2
Default Cache Policy: WriteBack, ReadAhead, Cached, Write Cache OK if Bad BBU
Current Cache Policy: WriteBack, ReadAhead, Cached, Write Cache OK if Bad BBU
Default Access Policy: Read/Write
Current Access Policy: Read/Write
Disk Cache Policy : Disabled
Encryption Type : None
Bad Blocks Exist: No
Is VD Cached: Yes
Cache Cade Type : Read Only

 

[cesarpk]

HI Unni

If you want the best performance and security of your data, i suggest to do these changes for all your virtual disks:

In the RAID controller:
1- Change "Write Cache OK if Bad BBU" to write cache off if Bad BBU - the default configuration of factory for avoid lost of data (in case of breakdowns or hangings)
2- Remove the cache policy "Readahead" - If the VM makes read cache in his RAM memory, why does it have a second read cache in the RAID controller?. - This is redundant, unnecessary, and it make to work more the Hardware, so will have more delay for get the data
2A- The speed of the memory RAM is +/- 1600 Mhz., and the buffer in the RAID controller is +/- 600 Mhz. RAM is always more fast
2B- The VM always search first in your cache that is in his RAM
2C- You will have more memory free for write data in the buffer of the RAID controller - get more speed for the writes
3- If is possible: "Disk Cache Policy : read" - never configure cache write if you want to avoid lost of data (in case of breakdowns or hangings)
4- Avoid to use RAID 0 - If a disk crashes, you will can not get access to your VD., more secure is to have raid 1, 5, 10, 50, 60. RAID 50 and 60 is the faster if you have many HDDs, with few HDDs RAID 10 is the best choice (redundant for security reasons and speed).

All the previously described is thinking if you have HDDs of platters and not SSD, with SSD disks, the configuration can be different.

5- About of Cache Cade: i don't have practices with these type of HDDs, but i know that these type of HDDS have little time to live in compare with the standard of HDDs of platters and is used for specific purposes (i think that the redundant is very important if you use these type of HDDs)
6- Also manufacturers of HDDs makes HDDs Hybrids, that is a mix of platters and SSD, but in this case the HDD put the the data of more use in the part of SSD, of this manner you get more speed of access. For this type of disks, the OS see it as a simple hard disk.

In the configuration of the Virtual disks of the VMs:

7- For avoid the lost of data (in case of breakdowns or hangings), you should configure the VM with access to disk as "directsync" or "writethroug". I think that "directsync" is better for avoid redundant write cache (RAM in Host and Buffer in RAID controller). - In anyway, if your RAID controller is configured as WriteBack, the VMs and the Host will think that the data is writes on the platter of the disk while that really the data is in the buffer of the RAID controller, and this last will know when the data will be writen in the platter of the HDDs, of this manner you will get a great performance for disk writes and the necessary security if the RAID controller is configured as i describe above.

I hope have helped you with this information

Best regards
Cesar

 

[udo]

... RAID 50 and 60 is the faster if you have many HDDs, with few HDDs RAID 10 is the best choice (redundant for security reasons and speed).

Hi,
why do you think that raid50/60 is faster than raid10? Normaly I would not agree - perhaps it's depends on the controller.

If you wan't speed, go for an good raidcontroller with fast sas-disks in raid10 - this in my opinion.

Udo

 

[cesarpk]

Hi,
why do you think that raid50/60 is faster than raid10? Normaly I would not agree - perhaps it's depends on the controller.

If you wan't speed, go for an good raidcontroller with fast sas-disks in raid10 - this in my opinion.

Udo

Hi Udo, that good to greet you again (you are a Master!!!)

I have understanding that if i have many HDDs in RAID 5, 50 or 60 (for example ten or more HDDs), the RAID controller writes the data in many little blocks of data simultaneously in the HDDs, so in this case, the write speed will be more fast that a single RAID-10, generally these RAID controllers that support many disks are of high performance, and with WriteBack cache included the performance will be better.

Or am I'm missing something?

Best regards
Cesar