MSA20 weird performance issues..

[Louis Henninger_1]

I have a DL380/G4 w add-on SA6402 controller. This is attached to an MSA20 enclosure with three 2TB disks (sata) in ARRAY config.
The disks have two logical drives, each one is RAID5. Drive 1 is 1.9TB and drive 2 is 1.8TB.
when I copy data from CD/DVD to drive 1 I average 10MB per sec. Doing the same operation to drive 2, I average 2MB per sec. I ran ADU and have it attached.

[Michael A. McKenney]

SATA, 3 drive, RAID 5 two arrays. The parity writes on SATA drives are your issue. It is not strange. I tested a MSA 2012fc 10 drive RAID 5 array and had 100 MB/s transfers. What stripe size did you use? Did you enable the cache? Does your controller have battery cache for better write performance. I would consider doing RAID 10 with four drives.

Microsoft does not support OS on RAID 5. RAID 1 or 10. Paging/swap files should be RAID 1 or 10. RAID 5 for either will cause excessive parity writes and really degrade performance.

[Louis Henninger_1]

Sorry...to clairfly....server has 2 disks internal configured Raid0+1 for O/S and page files, 3 more disks in Raid 5 (O/S volume D). The MSA20 is secondary DAS (E and F).

SA6402 has 128MB WBC w/battery, stripe size is 128K (default setting), read to write ratio is 30/70...was 50/50...no change. Then set to 10/90...no change...

Copy 1 GB file...less than 2 minute, 7GB file took 1hour +.

[Michael A. McKenney]

I usually use 64KB stripes for every RAID config. Windows 512KB clusters. Even on SQL and Exchange. I have done this for 20+ years.

Did you try copying from Drive C: to this drive?

Slow CD copying could be caused by how the CD/DVD was written. Factory disks are 1x for reliability. I would do a test RAID to RAID or across the wire from a desktop.

[Louis Henninger_1]

I'll try internal Raid 5 (disk D) to MSA (disk E) Then I'll try same test (disk D) to MSA (disk F).

I would've thought if problem was parity writes back to SATA's, my performance would be same no matter which disk I picked (E or F). I'll post results tomorrow, if possible.

Thanks,

Louis

[steve bryson]

I may have confused Louis when I emailed him the issue. We are not using a CD/DVD in the scenario we are writing from a PC to a share on a dl380 with an attached MSA20. Over the network write I am seeing 10mb per sec to one logical drive and 2mb per sec to another logical drive that are both part of the same array config. If I write to a share on the D drive which is a raid 5 on the dl380 not the MSA20 I am seeing 70mb per sec over the network. I also tried a copy from d(dl380) to f(msa20) and it took a little over an hour for a 7gb folder. server will hold a lot of large ISO files, 1gb to 7gb so should the stripe be larger rather than smaller?

[Michael A. McKenney · Accepted solution]

Three 2 TB drives.
Two logical drives about 1.8 and 1.9 on same array.

20+ years of SCSI. I started with 85MB SCSI I drives on Buslogic controllers in the 80s

The problem could be disk thrashing. In hardware RAID 5 on JBOD, it is best to have one partition only. You risk the drives fighting over r/w and parity writes between the two arrays. SATA drives don't have the performance and cache speed of SAS or SCSI. Even the new SATA drives can't compete end to end with SAS/SCSI.

You are moving the heads back and forth from 0-49% to 50-99% of the sectors each time across three drives, one cluster parity writes and two data writes/reads. SATA was not designed for this.

[Michael A. McKenney]

At home I use a LSI Logic MegaRAID 8708EM2 SAS RAID controller with 128MB DDR667 battery cache. A pair of Seagate 15K 300GB in RAID 1 for OS and data partitions, 10K Savvio for paging files and archive storage. I did not do RAID 5 becaue of write performance and Microsoft does not support OS or paging in RAID 5.

1.097GB/s cached reads and 850 MB/s cached writes on drive C: on 15K RAID 1. They are designed to handle a server. This is my CAD/Photoshop workstation. SAS allows me to do two partitions. On SATA and SCSI RAID, I do one partition per RAID array. Only in SAS RAID and a MSA SAN, I will do multiple arrays.