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5741
May 31st, 2013 06:00
sector\block\track\cyl relation in symmetrix,dmx,vmx
I was going though a old discussion
https://community.emc.com/message/400093#400093
and got this calculation :
Old Symms and DMX1-2:
1 sector = 512 bytes
1 block = 8 sectors = 4 kb
1 track = 8 sectors = 32 kb
1 cyl = 15 tracks = 480 kb
DMX3-4:
1 sector= 512 bytes
1 block= 8 sectors = 4 kb
1 track= 16 sectors = 64 kb
1 cyl = 15 tracks = 960 kb
so, In Symmetrix the basic addressable unit is sector or block ? and is this DMX3-4 calculation applicable for Vmax(10,20,40K) also ?
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Quincy561
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June 3rd, 2013 08:00
Block is 512 in DMX2 and below, 520 in DMX3 and above (except some AS400 volumes which have 8 more bytes)
A block is the smallest IO that a FBA host can read/write.
sergv1
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June 1st, 2013 03:00
DMX3 numbers still true for VMAX family.
Fenglin1
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June 2nd, 2013 20:00
Hi anoop_acr
I think the number you listed about the DMX1-2 and DMX3-4 is little different from which I got.
The Sector is the smallest unit referenced on disk. The back-end hardware will not transfer data in sizes smaller than one sector. A Cyclic Redundancy Check (CRC) is performed on every sector of data transferred between components within the array. If the check shows that data has been damaged, the array takes countermeasures, such as re-transmitting or marking a disk region as damaged. In DMX arrays up to the DMX-2, the sector size was 4 KB. With the DMX-3, the size was doubled to 8 KB.
A Track is composed of eight continuous sectors. When a track of disk data is being represented in cache, the storage location used is called a “slot.” Arrays up to the DMX-2 used track sizes of 32 KB; DMX-3 arrays and higher use 64 KB tracks.
A cylinder was 480 KB for open systems arrays up to the DMX-2. All cylinders are 960 KB for DMX-3 arrays and higher.
VMAX changed the block size from 512 bytes to 520 bytes for open system, the additional 8 bytes store the array integrity checking word.
anoop_acr
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June 3rd, 2013 08:00
Thanks Quincy56,
So what I was referring as a sector in my original post is block and blocks form a sector. Is that correct ?
is below calculation is correct ? I have a doubt here with vmax block size.
Non DMX3,4 and Vmax Models:
1 Block = 512bytes
1 Sector=8 blocks=512*8=4096bytes=4KB(1KB=1024bytes)
1 Track = 8 blocks=8*4KB=32KB
1 Cylinder = 15 tracks = 15*32KB=480KB
DMX3,4 and VMAX Models:
1 Block = 512bytes (I read in vmax one block has 520 bytes where 512 bytes for data and 8 for data integrity check)
1 Sector=8 blocks=512*8=4096bytes=4KB (1KB=1024bytes)
1 Track = 16 blocks=16*4KB=64KB
1 Cylinder = 15 tracks = 15*64KB=960KB
anoop_acr
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June 3rd, 2013 08:00
Thanks Fenglin for the reply.. Still I an confused here... do we still use the word block now ?
xe2sdc can you help me here..
Quincy561
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June 3rd, 2013 09:00
For "user" data, you can use 512 bytes = block.
Quincy561
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June 3rd, 2013 09:00
Looks correct
anoop_acr
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June 3rd, 2013 09:00
For Vmax series, do we need to take 1 Block = 520 bytes for doing above calculations ?
sangil01
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June 4th, 2015 08:00
Is the block size on a Vmax unchangeable. Is it set for 512 bytes.
Quincy561
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June 4th, 2015 11:00
@sangil01, is that a question? If so, the answer is no, it is not changeable.
Quincy561
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June 4th, 2015 11:00
Product guide on around page 19
http://www.emc.com/collateral/hardware/product-description/h6544-vmax-w-enginuity-pdg.pdf
sangil01
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June 4th, 2015 11:00
Yes, it’s a question about the VMAX and the block size. Can you direct me to a document where EMC states that?
Thank you in advance,
Gilberto Sanchez
Storage Administrator, Open Systems Disk Services || Wipro Data Center Services, Wipro Technologies
|| P: 936-525-0275 || gilberto.sanchez@wipro.com