Presentazione storage concetti base pdf

Considerazioni per la tipologia di Dischi da Utilizzare

Considerazioni di Base

• Dischi e LUN

• Livelli di Raid

• Path

• Mirroring Sincrono


• Average Seek Time : The time the read/write head needs to physically move to the

correct place.

• IOs per Second : The amount of operations a disk can handle per second.

• MBs per Second :The amount of data a disk can transfer per second.

In qualsiasi soluzione di Storage è necessario avere particolare attenzione nella scelta del

layout dei dischi.

Tipiche indicazioni di classificazione delle tipologie di Dischi


Tipiche indicazioni di classificazione delle tipologie di Dischi

Performance dei dischi SSD

Specifications

•Up to 550MB/s Sequential Read

•Up to 500MB/s Sequential Write

•Up to 55,000 IOPS 4k Random Read

•Up to 75,000 IOPS 4k Random Write

Normale disco da 2’’ per server fino d 512GByte


Nuove Soluzioni in tecnologia FLASH

Performance Board Flash

Specifications

Up to 1800 MB/s Sequential Read

Up to 1700 MB/s Sequential Write

Up to 140,000 IOPS 4k Random Write

Available in 240GB, 480GB, 960GB


Performance dei dischi SSD


Performance Board Flash


Layout di utilizzo delle varie tipologie di Raid in funzione del Tier di utilizzo

Le nuove Tecnologie SSD e Flash possono essere integrate nei Tier

Fino a 4 livelli di Tier SSD + SAS (15K) + SAS (10K) + SATA


Tanti dischi, meno capienti ma più veloci ….


Distribuzione dei Lun nei vari array

Example 1 – 15 Disks in 1 RAID Set, 1 LUN

exported to the pool

Pro:

• Good performance due to striping across 15 physical

spindles

• Small storage loss for RAID overhead (depending on chosen

RAID level)

Contro:

• DataCore has just a single I/O queue to the disks which may

result in congestion

• If one physical disk fails, the whole LUN is affected by RAID

rebuild

• RAID rebuild may take a long time on large RAID sets and

degrade performance



Example 2 -- 15 Disks in 1 RAID Set, 3 LUNs created from RAID set and exported to the pool:

Pro:

• Small storage loss for RAID overhead

(depending on chosen RAID level)

Contro:

• If one physical disk fails, all three LUNs are

affected by RAID rebuild

• RAID rebuild may take a long time on large

RAID sets and degrades performance

• The DataCore pool concept of distributing

allocated blocks conflicts with the RAID layout – creates additional seek and rotational latency on the physical disks, thus degrading

performance



Example 4 - No RAID level – “just a bunch of disks” (JBOD)

Pro:

• Full use of capacity

• Many I/O queues to disks

• Pool spreads loads across spindles

• Contro:

• One failed disk will affect the entire pool(s)

• Disk failure may cause long recovery time

• Bad blocks on disks are not recognized



Example 3 – 15 Disks in 3 RAID Sets, 1 LUN for each RAID Set exported to the pool:

Pro:

DataCore has three I/O queues to the disks.

The distribution algorithm spreads out the load across

LUNs and increase performance

A failed physical disk affects just one LUN

RAID rebuild is quicker with fewer disks.

Contro:

Greater storage loss for RAID overhead (depending

on RAID level)

Pro superano i contro, buon bilanciamento tra

costi e prestazioni e disponibilità.

Configurazione consigliata in questo tipo di

situazione.


Distribuzione dei Lun nei vari array e tipologia di Raid

RAID 0 – Striping:

Pro:

• Full use of capacity

• Highest write performance

• Highest read performance

Contro:

• Highest risk potential

• DataCore has just a single I/O queue to the disks

which may result in congestion

• One failed disk destroys all data in the pool

• Disk failure may cause long recovery time



RAID 1 – Mirroring:

Pro:

• High security level

• High sequential read/write performance

• High random read/write performance

• DataCore spreads load across all RAID1 sets

• Failed disk doesn’t significantly affect

performance

• Quick recovery from disk failure

Contro:

• 50% capacity loss

Recommended for non-mirrored volumes and

applications which cause lots of small random I/Os (like database and email applications). Pools

which contain numerous volumes accessed by many Hosts may experience highly random I/O too.



RAID 10 – Mirroring e Striping:

Pro

• High security level


• Highest random read/write performance

Contro

• 50% capacity loss

• Less I/O queues compared to multiple RAID1



RAID 5 – Striping with Parity:

Pro:

• Moderate capacity loss


• High random read performance

Contro:

• Low random write performance

• Moderate security level

• Failed disk / rebuild impacts performance

RAID 5 sets are good for applications with mainly

sequential I/O or highly random reads like file server, average loaded databases and so on.

Creating multiple, smaller RAID5 sets are preferred over fewer large ones


Pool Disk

L'algoritmo di piscina DataCore distribuisce i blocchi di dati allocati in tutti i dischi in una

pool.

Non ha poco senso avere più lento e più veloce o più grandi e più piccoli all'interno di un

livello. Se una capacità del Pool è destinata ad essere ampliata e non sono disponibili risorse

tipo dischi/tipo/capacità ecc, può essere utile creare un nuovo pool con migrazione di

dischi virtuali.

Scenari di implementazione della soluzione DataCore

Host Ridondati, Path Ridondati

Front-end Port Front-end Port

Mirroring Port

Back-end Port Back-end Port

Path


Esempio di utilizzo di DataCore con due Host di Virtualizzazione VMware


Autotiering


Autotiering – Come funziona


Autotiering e la distribuzione disco virtuale


Layout di un Mirroring Sincrono


Considerazioni per l’utilizzo un Mirroring Sincrono

Dark fibre links can be stretched up to 10 km (with 1300 nm laser) or 35 km (with 1550 nm laser). Adark fibre link of 35 km adds a latency of around 5 micro seconds per km. A microsecond (µs) is equal to one millionth of a second or

one thousandth of a millisecond (ms).

This means a dark fibre link of 35 km adds a latency of 5 µs * 35km * 8(trips)= 1400 micro seconds(µs) = 1.4 milliseconds (ms) Degradation of the signal along the cable; this tends to increase the longer the link and brings downreliability without extra hardware to correct the degradation. If the link (HBAs and FC switches, link hardware) has not enough FC Buffer Credit, latency can

increase. The faster FC speed you want to use (2Gbps, 4Gbps, 8Gbps etc.) and the longer the link the more FC Buffer Credits you will need to fully utilize the link.

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