MODELCAR.HK

My 2nd Head YOUTEK IG Extreme Pro

By admin, October 26, 2011 10:35 pm

After playing with Head YOUTEK IG Extreme Pro almost 3 weeks, I’ve decided it’s time for me to get an extra stick for spare in case my 1^st one broke as Head YOUTEK IG Extreme Pro is famous for eating strings.

It came to my attention someone has posted a 99.9% new IG Extreme Pro in a local tennis forum, so I contacted the seller directly and bought it without hesitation at almost 30% off the original price.

One of the most important reasons is because I do need an original Grip 3 IG Extreme Pro.

Originally I was thinking selling the original Grip 2 at the same tennis forum, and there was actually a NO Brain approached me asking for 50% off, then I found out it’s very easy to change the grip to a Grip 3 at a pro-shop, even better, I simply put an over grip on the of the Grip 2 solved the problem with $40.

After receiving the racket, I couldn’t be happier, as I found out it’s almost new, even newer than my 1^st one, absolutely no scratch on the bumper that makes me wonder if the previous owner actually went to court and hit the balls.

Then it’s the perfect Grip 3, I can feel it’s even a bit smaller than my DIY Grip 3.

Anyway, I do hope the pair will last for a long long time, probably another 20 years just like my beloved POG. Well, it may not be a good news for local pro-shop though.

Tennis (網球)

More Spindles Means More IOPS? RAID10 vs RAID50

Comments (2)

By admin, October 26, 2011 10:21 pm

I’ve asked Equallogic Support the following question today, it turns out I had wrong understanding about RAID10 before.

Client enviornment is running VMWare using EQL PS6000XV, 16 15K RPM disks (ie, 14 disks + 2 hot-spares)

In RAID10, there are 7 spindles as RAID10 only ultilizes half the disks, so there are only 7 spindles producing the atual IOPS.

In RAID50, all 14 spindles are used.

I/O pattern is mostly random (30% Read, 70% Write)

Does this mean in this case RAID50 is faster than RAID10 in terms of IOPS as there are 14 spindles in RAID50 compares to 7 spindles RAID10?

Reply from Equallogic’s US Support

The thing to remember here is that with RAID10 it will make two writes, one to each disk.

With RAID50, it will need to make the read/write/parity to all of the member disks in the raidset.

With Read/Write sequential IO, the difference would be minimal. With an environment as you described (virtual environment) where there are many small random I/Os, RAID10 will be quicker.

RAID10 will also be quicker if a drive fails whereas the performance with RAID5/50 is poor when the raidset is degraded and a rebuild is going on.

And of course, the space issue when considering RAID10 or RAID50 is a huge consideration

Then, I got an even better answer from a Dell storage expert in Hong Kong

Actually spindle in RAID10 is still 14, not 7; 7 is the capacity oriented view. We still consider using all disks during I/O.

But you may notice that above chart didn’t mention for Read performance? And yes, read performance for RAID 10 and RAID 50 or even RAID-5 will almost the same! The different will mainly focus on write.

RAID 50 is two RAID-5 and stripe, the RAID parity overhead will still exist across the disks; the more disks you have in the RAID group, the more overhead and performance penalty you have!

In RAID 10, every RAID group consists with two disks only, so overhead and performance penalty is minimum.