Quick Raid quiz :)

Posted by Jimmer on 05-Dec-2014 03:34

Hi, I have a quick Raid quiz and would appreciate the advice/feedback :)If you had 8 disks and no AI, would you go for 8 disks in Raid 10 for all areas OR 6 disks in Raid 10 for the data and 2 disks in Raid 1 for the BI?

P.S: I guess, ideally you would remove all Raid 1 and replace them with Raid 10. So it would be better to go for 10 disks, with the data on 6 disks in Raid 10 and the BI on 4 disks in Raid 10.

But the question here is if we're limited to 8 disks.

Thanks and have a good weekend!

Jimmer

OpenEdge RDBMS - Forum
Posted by ChUIMonster on 05-Dec-2014 07:27

On 12/5/14, 4:51 AM, Jimmer wrote:
Reply by Jimmer

:) some businesses do.


Businesses do foolish things.

That particular choice borders on suicidal.

Others use 3-5 online incremental backups during work hours to alleviate, so... :)


Very, very few modern businesses can actually "rekey" several hours of lost work.  And if external systems are involved reconciling the data feeds and safely eliminating duplicate transactions becomes quite a challenge with even the smallest window of lost data.

After-imaging is the DBAs best friend.  Running without it is stupid.

Consider that the AI are on separate disks, what would be your advice regarding the 8 remaining?


Knowing nothing else and having no insight into the workload or the application but extrapolating from "no ai" that it must be a relatively small and lightweight system I would build a single RAID 10.

Even if it is larger I would probably go that way.

Discrete disk for the BI file only really works if there is just a single database.  Many, possibly most, systems are composed of multiple databases and thus have multiple bi logs.  In those cases the benefits of having a single drive that is accessed mostly sequentially are lost so you are better off combining them all.

Of course gathering real data about the systems actual workload and performance could change my mind.

-- 
Tom Bascom
603 396 4886
tom@greenfieldtech.com

Posted by ke@iap.de on 05-Dec-2014 04:38

The answer depends on the read load. With higher number of physical reads, you will benefit from a separated write channel on separate disks. So when you can read most data from memory (>=99%) then the Raid 10 with all disks give you better overall performance.

But as you can see from my vague arguing, there may no final answer before you have a look at the server running the application... :)

Klaus

All Replies

Posted by James Palmer on 05-Dec-2014 03:38

I wouldn't ever have a situation where there is no AI so the question is moot.

Posted by Jimmer on 05-Dec-2014 03:50

:) some businesses do.

Others use 3-5 online incremental backups during work hours to alleviate, so... :)

Consider that the AI are on separate disks, what would be your advice regarding the 8 remaining?

Thanks

Jimmer

Posted by ke@iap.de on 05-Dec-2014 04:38

The answer depends on the read load. With higher number of physical reads, you will benefit from a separated write channel on separate disks. So when you can read most data from memory (>=99%) then the Raid 10 with all disks give you better overall performance.

But as you can see from my vague arguing, there may no final answer before you have a look at the server running the application... :)

Klaus

Posted by James Palmer on 05-Dec-2014 06:29

[quote user="Jimmer"]

:) some businesses do.

[/quote]

They shouldn't. There is no alternative to AI that is better or easier to implement. Using anything else on data that is important is folly and asking for trouble. If you are going to the trouble of working out disk configuration then you should also be enabling AI. It's not difficult, and the AI Archiver takes all the hard work out of managing the files. 

Incremental backups are the devil's work IMO. 

As for disk configuration, IMO, for data that is important it should all be on RAID10. 

Posted by ChUIMonster on 05-Dec-2014 07:27

On 12/5/14, 4:51 AM, Jimmer wrote:
Reply by Jimmer

:) some businesses do.


Businesses do foolish things.

That particular choice borders on suicidal.

Others use 3-5 online incremental backups during work hours to alleviate, so... :)


Very, very few modern businesses can actually "rekey" several hours of lost work.  And if external systems are involved reconciling the data feeds and safely eliminating duplicate transactions becomes quite a challenge with even the smallest window of lost data.

After-imaging is the DBAs best friend.  Running without it is stupid.

Consider that the AI are on separate disks, what would be your advice regarding the 8 remaining?


Knowing nothing else and having no insight into the workload or the application but extrapolating from "no ai" that it must be a relatively small and lightweight system I would build a single RAID 10.

Even if it is larger I would probably go that way.

Discrete disk for the BI file only really works if there is just a single database.  Many, possibly most, systems are composed of multiple databases and thus have multiple bi logs.  In those cases the benefits of having a single drive that is accessed mostly sequentially are lost so you are better off combining them all.

Of course gathering real data about the systems actual workload and performance could change my mind.

-- 
Tom Bascom
603 396 4886
tom@greenfieldtech.com

Posted by Jimmer on 08-Dec-2014 07:53

Ok then, I got the picture, specifically the AI one :))

Thanks for your time and guidance/help on the matter.

Jimmer

This thread is closed