topic Re: Problem MSA1500cs in Disk Enclosures

Problem MSA1500cs

Ivanov Aleksey — Mon, 05 May 2008 11:28:06 GMT

Sory for my bad English :)

I have a 24x750 Gb SATA disk on MSA1500cs .
I want to use it how ~16Tb logical drive...
The max LUN size is 2Tb ?
Then I have 8 2Tb logical drives...
I try to spanned it in one drive ... but the speed of copy files from drive is too low (8 Mb/s). If I create RAID 0 of this drives... then speed too low.

How I can do ~16Tb logical drive and don't reduse speed of transport of data ?:)

Re: Problem MSA1500cs

Patrick Terlisten — Mon, 05 May 2008 11:54:10 GMT

Hello,

which raid level did you use? How did you configured the arrays and logical drives??

It depends on you configuration how fast it is. You should distribute the arrays / logical drives across the shelfs. Use RAID 5 or RAID 1 instead of RAID ADG. Use only one logical drive per array. You should create arrays with eight or twelve drives and create two or three logical drive with RAID 5 in it. I don't think that you can use 16 TB, because you can only handle 2 TB per logical drive. Because of the drive size, you can use 1,5 TB, or with bigger drives, you loose space if you want equal sized logical drives.

Hope this helps.

Best regards,
Patrick

Re: Problem MSA1500cs

Ivanov Aleksey — Tue, 06 May 2008 04:50:43 GMT

With RAID 5.
I create array A - all drives, and at this array I create 8 logical drives.
If I create Array of all drives and create 1 logical drive (10 Gb for test), when upload on this logical drive is 50Mb/s, download 10 Mb/s...
I afraid trouble in MSA1500 ... or HP proliant server.

Re: Problem MSA1500cs

Ivanov Aleksey — Tue, 06 May 2008 05:22:38 GMT

I create 1 array of 3 phisycal drives (750Gb) ... create logical drive RAID 5 (100Gb) ... and speed too low again :(

Re: Problem MSA1500cs

Patrick Terlisten — Tue, 06 May 2008 06:26:54 GMT

How did you test it??

A SATA drive can deliver round about 100 IOPS. With 24 drives you will get round about 2400 IOPS. If each IO has a size of only 4 KB, you will get only round about 9600 KB/s, if you read from all 24 drives. Now you got a RAID 5 with 24 drives. You will read effective only from 23 drives, cause 1 drive keeps the parity block. If you write to that RAID, it's getting much more complicate: A logical write IO in a RAID 5 is divided into two physical read, and two physical write IOs. So you use only 25% of your possible IOPS. Back to you 2400 IOPS: If you do a write IO on that RAID 5, ony 600 IOPS will be used. 600 IOPS x 4 KB Transfersize = 2400 KB/s. If you get only 10 MB/s, your average transfer size is round about 17 KB. That's equal to your read performance: You get round about 50 MB/s, so your transfer size is round about 22 KB.

Your performance depends on you application, how it access the storage and what kind of IO will be done.

Hope this helps.

Best regards,
Patrick