I'm setting up a new web server that is going to be running ASP.Net 2.0 website with a SQL Server 2005 database. The server has two physical SATA drives. It will not be possible to add more drives to the server, so my question is...
Would it be better to use the two drives as two separate drives with the SQL log files and data files on separate drives, or would it be better to set the two drives up in a RAID configuration and just keep the files together on the same drive?
If the RAID option is better, then should it be a RAID 0 or RAID 1?
The server has a 2Ghz Xeon Processor with 4GB of memory.
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Not Raid 5 - Please !!!
Mirroring is best for security and redundancy purposes - it 1 drive fails, bung in another and life goes on.
However, that would mean all system, logs, data and transient space as well as virtual memory is going on the one spindle and sata aint that fast !
So, you are going to have to rely on backups and have the two disks just as drives, and build a very very tight Disaster Recovery plan to make very sure that your recovery process enables re-entry of missing data since last backup. Can you get an external big drive ? You can trickle feed in background regular backups of your more critical files.
The failure rate of drives is improving no end, but doesn't mean it doesn't happen.
What is the machine used for ?
@mark wills:
The machine is a web server that is going to host an ASP.Net web application for an electronic recycling company. The app handles everything from shipments to invoicing and payments.
We already do nightly backups on the app's current server, and would continue the same for the new server.
How much of a performance difference would there be between a RAID configuration with logs, data etc on the same drive and a two drive system?
Thanks!
IT depends on what type of activity you have...if not a lot of reads/writes, then hardly no difference. If you ahve a lot of transactions and reads and writes, then substantial if they are on the same drive...the reason is that writes to the trans log are sequential in nature, whereas writes to the data files are random, along with random reads.
Agree with chapmandew - and I was going to try hard not to today :)
Is it just internal, or is the site exposed to customers ?
How many transactions per day would you say - how big do you think the DB will get ?
How are the transactions captured into the system (retyping paperwork or direct entry) ?
If you can keep the database very clean, it will spend a fair bit of time in memory. So read performance should be OK. But write performance is the slow bit. Sata drives are not that quick, and given the nature of this discussion, you probably don't have write caching enabled on you IO cards.
Also, having IIS and SQL Server on the one machine exposed to the outside world is not particularly safe. You will need to lock it down.
What would happen to the business if the box went down for a few hours ?
Some RAID facts... Over simplification as it may be...
Raid 0 and Raid 5 are based on striping technology - meaning they try to achieve a level of concurrency by distributing data across spindles. That does make it quicker for retrieval, but slower for writing because it hast to map where the data streams go, and create parity check digits etc etc... Raid 5 is a bit worse because it goes a lot further in its parity checking - and really needs three disks.
Raid 1 is basic mirroring. Meaning write it to a disk, and it gets copied to the other. One of them fails the other kicks in. Like Raid 0 , needs 2 disks or multiple pairs.
Raid 10 is a pair of striped disks being mirrored - needs at least 4 disks and has the speed of striping with the security of mirroring. The more spindles the better - but then capacity can look a bit silly.
Any RAID Must be Hardware Raid - if it is software raid, then we can stop right now.
Striping raid technologies are hard to recover because it has to re-establish parity and checks.
Therefore mirroring is the only real basis for raid because of the additional security in having redundancy - disks have significantly outgrown the origins of raid way back when a 9 gig disk was huge, and the only way to get a 10 gig database was to have raid.
Disks are now very big, so it is not the normal reason for Raid anymore. So it is a question of performance over reliability.
It is probably not the logs and data as much as the system files for memory and paging. Especially with a web server which tends to be a bit more slap happy with memory and will page requests in and out - meaning disk activity flushing memory back to disk. SQL on the other hand, wants to grab a few gig and play in that space. So already we can see a little bit of contention. Combined with Kernel mode IO activity whilst trying to commit a humble invoice, there is even more contention. And disk IO is the slowest part of any system today...
The calculated trade off has to be performance over reliability. That also include user experience and continuity of service.
Apologies for the diatribe...
It sounds to me like there would most likely be a significant performance increase due to having the log and data files on different drives, but only at a cost to reliability because of the lack of a RAID setup.
So, basically it's just a judgment call between performance and reliability.
Thanks for the input... I'll leave this question open a little while longer just in case anyone else has more input.
Thanks!
I'm guessing that I'm not going to get any more responses on this, so I'm going to go ahead and close the question.
Honestly, my boss had already made up his mind before I asked this question, so the server is already in a raid configuration with both the log and data files on the same drive. I just wanted to see if there actually is a significant performance increase the other way.
Thanks for your input! I'll reward equal points for each post that has good information in it.
Thanks,
Jeff
Business Accounts
Answer for Membership
by: chapmandewPosted on 2008-04-17 at 14:29:28ID: 21381537
I would create them as a RAID container, with RAID 10 (if you can afford it). It provides max redundancy and max peformance.