Which EXP810's Disk Drive to choose?

[khalidaaa]

I didn't mean to cross-post or any thing but could any body help me with this as i need to buy the disks urgently.

http://www.tek-tips.com/viewthread.cfm?qid=1530028&page=1

I couldn't have any help since yesterday on that forum!

Regards,
Khalid

 

[mrn]

Hi Khalid,

Try taking a look at

http://www.storageperformance.org/results/benchmark_results_spc1

Mike

"Whenever I dwell for any length of time on my own shortcomings, they gradually begin to seem mild, harmless, rather engaging little things, not at all like the staring defects in other people's characters."

 

[khalidaaa]

Thanks Mike for the nice link. I went through the report but i really couldn't find what i'm looking for. The link shows the different LUN sizes performance for 36GB disks only!

Any other thoughts?

Regards,
Khalid

 

[p5wizard]

How much cache do you have in your controllers?

All FC options are 15krpm, so for production databases I'd go for the 146GB or even 300GB disks depending on your cache size and/or cache-(un)friendliness of your server applications.
If your controllers are low on cache, perhaps the 73GB disks must be your choice for production systems.

For Dev/Test, the 300GB or 450GB are probably OK.

For data archiving purposes (no read or write performance constraints), you may want to go for the SATA disks.



HTH,

p5wizard

 

[khalidaaa]

I don't remember to be honest! As per this document:

http://www.nasi.com/IBM_DS4500.php

The maximum cache is 2GB (I guess ours is 1GB). I will have to confirm this.

Whatever you say p5wizard i take it for granted But do you have any official document on this to present it to our IT Infrastructure head?

Thanks

Regads,
Khalid

 

[p5wizard]

How about this?

http://www.redbooks.ibm.com/abstracts/tips0458.html?Open

If you google for "FC SATA comparison", there 's a whole bunch of other information.

They need hard figures? FC disks run at 15000rpm, SATA disks run at 7200rpm. Databases need high disk speed and low disk seek times!


HTH,

p5wizard

 

[khalidaaa]

Our Cache is 1GB as i expected!

Thanks p5wizard but i went through the document and it still doesn't answer my query

One thing i got out of it which says RAID10 performance is higher than RAID5.

I wonder if any body has the 146GB configuration so we can run few tests here and there and just compare the data!

Regards,
Khalid

 

[p5wizard]

We run all prod databases on RAID5 LUNs on 146GB 15krpm disks, but they are in DS8k with loads more cache than you have, so you can't really compare.
73GB 15krpm would be overkill in a DS8k IMHO. in a DS4k with just 1GB of cache? I don't know...


HTH,

p5wizard

 

[p5wizard]

Can't you ask IBM or your business partner for help in setting up a test environment? Or maybe a Try&Buy offer?



HTH,

p5wizard

 

[khalidaaa]

We usually don't get into that many questions when buying stuff but during this economic climate, it is a horrifying decision to upgrade machines!

I've sent to that query to IBM but they came back with refferal to the salesperson i'm dealing with! I'm looking for a neutral suggestion!

I asked our salesperson to provide me with the transfer rate for each option and see what is the difference! I'm still with the first option as it logically provides the fastest seek time.

I was monitoring the cache hit percent for some of the production LUNs and i've noticed that we have an average of 30% cache hit which suggest that it's better to go with the first option for this type of data.

What do you think?

Regards,
Khalid

 

[p5wizard]

With low cache hit ratio, it's better to go for disks with lowest seek times, best transfer rates and as many spindles as possible.

Then it's probably up to your boss to trade off $ per GB versus performance per $ ...


HTH,

p5wizard