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

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

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Duncan Meyers

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sk391

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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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Member_2_231077

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sk391

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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?

sk391

ASKER

sorry i meant to split the points.. I am asking a moderator to help.

Member_2_231077

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.

sk391

ASKER

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)

Duncan Meyers

... 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