which is better: seperate raid drives or 1 raid drive with partition

[overdraft015]

Is there any difference between having say 4 physicals disks into 1 raid disk split into two partitions or 4 physicals disks into 2 raid disks.

both senarios give the os the appearance of two disks but is there any performance difference?

Our usual reason for wanting two "disks" per server is C:\ drive will be the OS and D:\ will be the data for the apps. e.g. active directory, file shares, web pages etc...

just not sure which would be the best config. also should i be choosing a difference raid levels for the os and the data for better performance?

Thanks for those that can offer help.

Michael.

It's not what you know. It's who's on Tek-Tip's

 

[technome]

4 physical disks in raid 1 is referred to as raid 10.

Raid 10 will be much faster then a 2 disk raid 1. In raid 1, only 1 of the two disks is read from a mirrored set. In a 4 drive raid 10, multiple drives are read at the same time. Writes have a penalty over a single drive as the 2nd drive of mirror set(s) need to be written to after the data is written to the first member of mirror set; if disk traffic is low, this is basically negated by the raid cards cache.

Your best bet is to go a 4 disk raid 10, with 2 partitions. One for the OS, one for data. Included in the OS partition is any Active directory files, which are by default included in the OS partition.

........................................
Chernobyl disaster..a must see pictorial

http://www.kiddofspeed.com/default.htm

 

[overdraft015]

Thanks technome,

what if some servers have 5/6 disks available. what would the best solution be then? also would all the disks need to be of the same size? to have 1 raid drive then multiple partitions?

some servers for example have 2 x 9.1GB/18.2GB/36GB/72GB drives (D:\) and 4 x 36GB/72.8GB/146GB/300GB drives (D:\)

It's not what you know. It's who's on Tek-Tip's

 

[technome]

1) Any drives less then 36 Gig are fairly old and damn slow, I would dump them.

2) if you have 6 disks, I would create two arrays. A raid1 (2 disks ) for the OS, then 4 in raid 10. You also have the option of creating raid 5 arrays, which would save on the number of drives used in array, but raid 10 generally beats raid 5 in overall performance.

3) In an individual array, all drives in should be the same size, or the array is limited in size by the smallest disk's capacity. EG 4 drive raid, 3 drives 160 Gig , 1 drive 60 Gig, end result you would only get a 120 Gig array, as only 60Gig out of each 160Gig drive could be used in the array.

4) An array, be it raid 1, 10, 5 etc is treated by an OS as a single drive; Os do not know about the individual disk in an array set. You can have many partitions.



........................................
Chernobyl disaster..a must see pictorial

http://www.kiddofspeed.com/default.htm