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07-06-2005, 11:57 PM #1WHT Addict
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if my database is small enough to fit in memory, do i need to bother with scsi?
i run a php/mysql driven site and my database is small enough that it fits in the memory of the system. does this mean, scsi would not benefit me much?
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07-07-2005, 12:36 AM #2rogue element
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(I'm going to pretend he's asking if he needs RAID, not SCSI. )
You still need RAID. When the machine is rebooted, what happens to that database held in memory? It's written to disk before shutdown. Let's say the HD fails upon restart. Where's your data now?
Ideally, on the rest of the RAID array, so you can reconstruct. What if you only have a single HD? Better have a current backup. When you backed up that database, the data wasn't read from memory, it was read from disk. If the HD fails and corrupts data, it's the corrupted data from the disk that's backed up, not the correct data in memory.
There's always a benefit to using a RAID array.Eric J. Bowman, principal
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07-07-2005, 12:44 AM #3WHT Addict
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i backup the data seperately so i don't need raid. i do need high performance and many say scsi is better for database servers.
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07-07-2005, 12:50 AM #4Web Hosting Master
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Technically speaking, if you have a very active website which is database intensively, it would inevitably means that it would access the harddisk quite often and a SCSI because of its built-in disk controller, it would reduce the load on the server's CPU. This means that the CPU can be free to handle other activities.
However, that is only useful when your activity is very high. An IDE would handle most of the requirement. If you don't want SCSI then you don't need to. The only thing is that there may be a couple of seconds slowdown during heavy activities.
Like you say if you load the database to memory then there would in theory not be a need for a fast harddisk. However as all database intensive sites, it would require a fast CPU to handle the server. It all depends on your load.
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07-08-2005, 12:14 AM #5Web Hosting Master
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Originally posted by BigBison
When you backed up that database, the data wasn't read from memory, it was read from disk. If the HD fails and corrupts data, it's the corrupted data from the disk that's backed up, not the correct data in memory.
Write activity still must pushed to disk at some point. If you have a significant update/insert load, disk IO could still be a bottleneck. Generally, if you sustain more than 500k/sec of IO, I recommend SCSI. Otherwise, that money is better spent elsewhere.Game Servers are the next hot market!
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07-08-2005, 03:17 AM #6rogue element
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Originally posted by hiryuu
Any data that's in disk cache...
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07-08-2005, 03:55 AM #7Junior Guru
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If u can fit database in memory then your DISK speed will not be important.
Let say your databse is 10 MB in size.
Only time when your hard drive will be accessed is for system files from OS or for static pages if u host on same server.
Also u should think about this - how much often u will write down (dump) databse back to hard drive.
Cause if your server crash or whatver (reboot etc) - u will lose all your data.
We have solution for some of our clients that database is writen down to hard drive every 5 minutes from memory.
So in worst case u will lost 5 minutes of data. In same case we have set that each time there is some "write" in database we are doin dump on harddrive to prevent any loss of data.
Database from memory really works great, your website can really work fast this way, but u need to take care of your data in case something bad happen.
Bottom line - if u doin what u doin - u dont need SCSI - but cant hurt
N.
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07-08-2005, 09:45 AM #8Temporarily Suspended
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we have compared 2 servers: P4 3GHz with IDE HDD, and P3 733 with SCSI HDD. The server load in P4 is around 0.3. And in P3 is around 0.2. Customers in P3 box are much happier than other.
I am a big fan of SCSI