IOPS, latency, disk access time, for HP 2TB 6G SAS 7.2K LFF DP MDL (AW555A)

Posted on 2014-01-31
Last Modified: 2014-02-04
Hello, are there published performance numbers for HP's AW555A 3.5 inch disk drives, such as read/write IOPS, etc?

We will be using them in RAID10 on a P2000 (SAS) array and I wanted to see what their performance is going to be like.

Thank you
Question by:sk391
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by:Duncan Meyers
Duncan Meyers earned 200 total points
ID: 39826193
Manufacturers stopped publishing performance numbers some time ago - I guess probably because their customers expected their products to achieve the inflated numbers  their marketing departments  came up with.  :-)

Use 60 - 80 IOPS for a 7200rpm SATA drive. Expect latency to be in the order of 5-10mS up to about 100 IOPS  per drive then latency will climb.

What workload are you intending to run on the drives? Remember that SATA drives are not built for random workloads and they don;t perform particularly well with those loads.

Author Comment

ID: 39826229
Thank you! I intend to use these mostly for Tier-2 storage on VMware (ESXi 5.1).

The same P2000 also has 12x 600GB SAS 15k RPM disks, which are mostly used for O/S and databases (1 RAID10 vdisk, 6 LUNs presented to the ESXi hosts)

So for example non-demanding workloads, like data disks / backups inside the guest OS of the VM's will be using this new storage tier. The average tenant pool will be around 1TB of 7.2k rpm storage , and 300-400GB of 15k rpm storage.

I noticed you mention SATA but these are actually SAS 7.2 rpm drives, which should be good for error monitoring/reliability I believe?

Overall the only objective is archival-class storage for these disks, just wanted to have a rough idea of the performance so we know when to add one more disk enclosure..
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Accepted Solution

andyalder earned 300 total points
ID: 39826470
IOPS for a fully configured P2000 MSA G3 are published but it's stuffed with 15K disks.

Rotation and average seek for the disks is published in , you can work out raw IOPS, access time and latency from that but it doesn't take into account the controller's cache nor re-ordering requests to cut down on long seeks.

Author Comment

ID: 39826523
thanks thats exactly what i was looking for!

I see for HP 2TB 6G SAS 7.2K rpm LFF (3.5-inch) SC Midline 1yr Warranty Hard Drive 507616-B21,

Seek Time (typical reads, including settling)

Single Track 0.7 ms
Average 8.5 ms
Full-Stroke 18.2 ms
Rotational Speed 7200 rpm

Physical Configuration Bytes/Sector 512
Logical Blocks 3,907,029,168

No mention of IOPS, but like you said around 70 mixed iops per drive would be a safe assumption?
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Author Comment

ID: 39826526
sorry i meant to split the points.. I am asking a moderator to help.
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Expert Comment

ID: 39826572
Calculate IOPS: 60/7200=8.3ms for a full revolution but on average you only need to go half way around so rotational latency = 4.15ms, add 8.5ms average seek = 12.65ms for one I/O 1000/12.65=79 IOPS - but write IOPS are lower than that due to a longer settle time being needed to make sure you write in the middle of the track and also it doesn't take into account the data transfer time. 70 IOPS for a 7.2K disk is a good rule of thumb.

Author Comment

ID: 39826702
Thanks andyalder, for archival/backup data it should be fine then, thank you...

I've seen on average most windows 2008/2012 server VM's are using ~30 IOPS on a 24hr period, so with 12x disks @ 75 iops each we should be able to run around 30 windows server VM's on our hosts using this storage, and around 80 windows server VMs on the 15k rpm storage (roughly)

The P2000 has two controllers, if I understand the documentation correctly I have the ability to assign resources to a specific storage controller (at the vDisk level), so I will try to set

Controller1 -> vDisk1 (12x 15k rpm disks, raid10, 3.6TB usable)
Controller2 -> vDisk2 (12x 7.2k rpm disks, raid10, 12TB usable)
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Expert Comment

by:Duncan Meyers
ID: 39826898
... that's where 60-180 IOPS comes from. The main contributor is the drive's spin speed. There's a bit of variation in average seek time across drives but it's pretty small

SAS and FC disks will maintain two to two and a half times the calculated performance. SATA drives will max out at about two times before latency goes through the roof

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