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Adding capacity – performance impact

Experts! I have a challenge. I have an existing system to which I need to add storage capacity, for the best possible performance per dollar. I have two drive cabinets, each having a capacity of 14 drives, each with 8 bays full. The drives are 72GB each, the raids are in a 0 + 1 configuration. That has given us 271 GB storage each cabinet, for a total of 542 GB. We use this storage for both data and backups. It’s worked great, but it’s getting full. Here are my thoughts: 1. Just fill the rest of the bays with new drives of the same size. Works, but it’s still too small for 12 months projected growth. 2. Remove existing drives from one, and put 6 of them in the other. Then fill the newly-empty cabinet with bigger (144 GB?) drives. I worry about a performance hit with the bigger drives. Should I worry? 3. Add another controller and drives for an additional volume, dedicated only to backups. Save some bucks by making the additional volume somewhat less robust, since backup will be its only function. 4. Aquire Litespeed. Which is the best?
my preference is to use all available drives for data & tempdb, excluding disks dedicated to logs this usually implies the following
on each RAID array (comprised of several disks)
create 1 partition for data (or 1 partition for each file group)
one partition for tempdb
one partition for backups another option is as follows
on a common set of disks
create 1 RAID 10 array for partitions containing active data and tempdb
create 1 RAID 5 array for partitions containing data with little write activity and backups for low cost, consider first reconfiguring the arrays, fill the remaining drive bays, get LS
for future expansion, stop buying additional SCSI storage and start on SAS storage cabinets usually i like to have enough storage for 2 full backups
but having LS let me keep several backups
Thanks Joe – good advice as always. Along with LS, which of these two options would you recommend?: A. Add 12 72GB drives to the current cabinets we have, as volumes D and E. Current storage is 271 GB * 2 cabinets = 542 GB With the additional drives, the capacity becomes 474 GB * 2 cabinets = 948 GB. or B. Empty one of the existing cabinets (E) and move 6 of its 8 existing drives to the other (D). That would make one cabinet for drive D with capacity 474 GB. Fill the empty cabinet with new 144 GB drives. That would yield a second volume having ~1,000 GB of capacity. Is option B likely to entail a performance hit? Or would 144GB drives deliver close to the same performance as the 72’s?

assuming the data is split into multiple files, each file should reside on a disk array with reasonably comparable performance, unless you will accept unbalanced performance assuming both are 10K, there is no difference on size,
except that if you use 50% of a 73G and 25% of a 146G, the 146G will have slightly better random IO because the seek times will be less